Revert "more: exit if POLLHUP or POLLERR on stdin is received"

[thirdparty/util-linux.git] / text-utils / more.c

/*
 * Copyright (C) 1980 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

/* more.c - General purpose tty output filter and file perusal program
 *
 * by Eric Shienbrood, UC Berkeley
 *
 * modified by Geoff Peck
 *      UCB to add underlining, single spacing
 * modified by John Foderaro
 *      UCB to add -c and MORE environment variable
 * modified by Erik Troan <ewt@redhat.com>
 *      to be more posix and so compile on linux/axp.
 * modified by Kars de Jong <jongk@cs.utwente.nl>
 *      to use terminfo instead of termcap.
 * 1999-02-22 Arkadiusz Miśkiewicz <misiek@pld.ORG.PL>
 *      added Native Language Support
 * 1999-03-19 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
 *      more nls translatable strings
 * 1999-05-09 aeb
 *      applied a RedHat patch (setjmp->sigsetjmp); without it a second
 *      ^Z would fail.
 * 1999-05-09 aeb
 *      undone Kars' work, so that more works without libcurses (and
 *      hence can be in /bin with libcurses being in
 *      /usr/lib which may not be mounted).  However, when termcap is not
 *      present curses can still be used.
 * 2010-10-21 Davidlohr Bueso <dave@gnu.org>
 *      modified mem allocation handling for util-linux
 */

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdarg.h>
#include <sys/param.h>
#include <ctype.h>
#include <signal.h>
#include <errno.h>
#include <fcntl.h>
#include <termios.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <sys/ttydefaults.h>
#include <sys/wait.h>
#include <regex.h>
#include <assert.h>
#include <poll.h>
#include <sys/signalfd.h>
#include <paths.h>
#include <getopt.h>

#if defined(HAVE_NCURSESW_TERM_H)
# include <ncursesw/term.h>
#elif defined(HAVE_NCURSES_TERM_H)
# include <ncurses/term.h>
#elif defined(HAVE_TERM_H)
# include <term.h>
#endif

#ifdef HAVE_MAGIC
# include <magic.h>
#endif

#include "strutils.h"
#include "nls.h"
#include "xalloc.h"
#include "widechar.h"
#include "closestream.h"
#include "env.h"

#ifdef TEST_PROGRAM
# define NON_INTERACTIVE_MORE 1
#endif

#define BACKSPACE       "\b"
#define CARAT           "^"

#define ARROW_UP        "\x1b\x5b\x41"
#define ARROW_DOWN      "\x1b\x5b\x42"
#define PAGE_UP         "\x1b\x5b\x35\x7e"
#define PAGE_DOWN       "\x1b\x5b\x36\x7e"

#define MIN_LINE_SZ     256     /* minimal line_buf buffer size */
#define ESC             '\033'
#define SCROLL_LEN      11
#define LINES_PER_PAGE  24
#define NUM_COLUMNS     80
#define TERMINAL_BUF    4096
#define INIT_BUF        80
#define COMMAND_BUF     200
#define REGERR_BUF      NUM_COLUMNS

#define TERM_AUTO_RIGHT_MARGIN    "am"
#define TERM_BACKSPACE            "cub1"
#define TERM_CEOL                 "xhp"
#define TERM_CLEAR                "clear"
#define TERM_CLEAR_TO_LINE_END    "el"
#define TERM_CLEAR_TO_SCREEN_END  "ed"
#define TERM_COLS                 "cols"
#define TERM_CURSOR_ADDRESS       "cup"
#define TERM_EAT_NEW_LINE         "xenl"
#define TERM_EXIT_STANDARD_MODE   "rmso"
#define TERM_HARD_COPY            "hc"
#define TERM_HOME                 "home"
#define TERM_LINE_DOWN            "cud1"
#define TERM_LINES                "lines"
#define TERM_OVER_STRIKE          "os"
#define TERM_STANDARD_MODE        "smso"
#define TERM_STD_MODE_GLITCH      "xmc"

/* Used in read_command() */
typedef enum {
        more_kc_unknown_command,
        more_kc_colon,
        more_kc_repeat_previous,
        more_kc_backwards,
        more_kc_jump_lines_per_screen,
        more_kc_set_lines_per_screen,
        more_kc_set_scroll_len,
        more_kc_quit,
        more_kc_skip_forward_screen,
        more_kc_skip_forward_line,
        more_kc_next_line,
        more_kc_clear_screen,
        more_kc_previous_search_match,
        more_kc_display_line,
        more_kc_display_file_and_line,
        more_kc_repeat_search,
        more_kc_search,
        more_kc_run_shell,
        more_kc_help,
        more_kc_next_file,
        more_kc_previous_file,
        more_kc_run_editor
} more_key_commands;
struct number_command {
        unsigned int number;
        more_key_commands key;
};

struct more_control {
        struct termios output_tty;      /* output terminal */
        struct termios original_tty;    /* original terminal settings */
        FILE *current_file;             /* currently open input file */
        off_t file_position;            /* file position */
        off_t file_size;                /* file size */
        int argv_position;              /* argv[] position */
        int lines_per_screen;           /* screen size in lines */
        int d_scroll_len;               /* number of lines scrolled by 'd' */
        int prompt_len;                 /* message prompt length */
        int current_line;               /* line we are currently at */
        int next_jump;                  /* number of lines to skip ahead */
        char **file_names;              /* The list of file names */
        int num_files;                  /* Number of files left to process */
        char *shell;                    /* name of the shell to use */
        int sigfd;                      /* signalfd() file descriptor */
        sigset_t sigset;                /* signal operations */
        char *line_buf;                 /* line buffer */
        size_t line_sz;                 /* size of line_buf buffer */
        int lines_per_page;             /* lines per page */
        char *clear;                    /* clear screen */
        char *erase_line;               /* erase line */
        char *enter_std;                /* enter standout mode */
        char *exit_std;                 /* exit standout mode */
        char *backspace_ch;             /* backspace character */
        char *go_home;                  /* go to home */
        char *move_line_down;           /* move line down */
        char *clear_rest;               /* clear rest of screen */
        int num_columns;                /* number of columns */
        char *next_search;              /* file beginning search string */
        char *previous_search;          /* previous search() buf[] item */
        struct {
                off_t row_num;          /* row file position */
                long line_num;          /* line number */
        } context,
          screen_start;
        unsigned int leading_number;    /* number in front of key command */
        struct number_command previous_command; /* previous key command */
        char *shell_line;               /* line to execute in subshell */
#ifdef HAVE_MAGIC
        magic_t magic;                  /* libmagic database entries */
#endif
        unsigned int
                bad_stdout:1,           /* true if overwriting does not turn off standout */
                catch_suspend:1,        /* we should catch the SIGTSTP signal */
                clear_line_ends:1,      /* do not scroll, paint each screen from the top */
                clear_first:1,          /* is first character in file \f */
                dumb_tty:1,             /* is terminal type known */
                eat_newline:1,          /* is newline ignored after 80 cols */
                erase_input_ok:1,       /* is erase input supported */
                erase_previous_ok:1,    /* is erase previous supported */
                exit_on_eof:1,          /* exit on EOF */
                first_file:1,           /* is the input file the first in list */
                fold_long_lines:1,      /* fold long lines */
                hard_tabs:1,            /* print spaces instead of '\t' */
                hard_tty:1,             /* is this hard copy terminal (a printer or such) */
                leading_colon:1,        /* key command has leading ':' character */
                is_eof:1,               /* EOF detected */
                is_paused:1,            /* is output paused */
                no_quit_dialog:1,       /* suppress quit dialog */
                no_scroll:1,            /* do not scroll, clear the screen and then display text */
                no_tty_in:1,            /* is input in interactive mode */
                no_tty_out:1,           /* is output in interactive mode */
                no_tty_err:1,           /* is stderr terminal */
                print_banner:1,         /* print file name banner */
                reading_num:1,          /* are we reading leading_number */
                report_errors:1,        /* is an error reported */
                search_at_start:1,      /* search pattern defined at start up */
                search_called:1,        /* previous more command was a search */
                squeeze_spaces:1,       /* suppress white space */
                stdout_glitch:1,        /* terminal has standout mode glitch */
                stop_after_formfeed:1,  /* stop after form feeds */
                suppress_bell:1,        /* suppress bell */
                wrap_margin:1;          /* set if automargins */
};

static void __attribute__((__noreturn__)) usage(void)
{
        printf("%s", USAGE_HEADER);
        printf(_(" %s [options] <file>...\n"), program_invocation_short_name);

        printf("%s", USAGE_SEPARATOR);
        printf("%s\n", _("Display the contents of a file in a terminal."));

        printf("%s", USAGE_OPTIONS);
        printf("%s\n", _(" -d, --silent          display help instead of ringing bell"));
        printf("%s\n", _(" -f, --logical         count logical rather than screen lines"));
        printf("%s\n", _(" -l, --no-pause        suppress pause after form feed"));
        printf("%s\n", _(" -c, --print-over      do not scroll, display text and clean line ends"));
        printf("%s\n", _(" -p, --clean-print     do not scroll, clean screen and display text"));
        printf("%s\n", _(" -e, --exit-on-eof     exit on end-of-file"));
        printf("%s\n", _(" -s, --squeeze         squeeze multiple blank lines into one"));
        printf("%s\n", _(" -u, --plain           suppress underlining and bold"));
        printf("%s\n", _(" -n, --lines <number>  the number of lines per screenful"));
        printf("%s\n", _(" -<number>             same as --lines"));
        printf("%s\n", _(" +<number>             display file beginning from line number"));
        printf("%s\n", _(" +/<pattern>           display file beginning from pattern match"));
        printf("%s", USAGE_SEPARATOR);
        printf(USAGE_HELP_OPTIONS(23));
        printf(USAGE_MAN_TAIL("more(1)"));
        exit(EXIT_SUCCESS);
}

static void argscan(struct more_control *ctl, int as_argc, char **as_argv)
{
        int c, opt;
        static const struct option longopts[] = {
                { "silent",      no_argument,       NULL, 'd' },
                { "logical",     no_argument,       NULL, 'f' },
                { "no-pause",    no_argument,       NULL, 'l' },
                { "print-over",  no_argument,       NULL, 'c' },
                { "clean-print", no_argument,       NULL, 'p' },
                { "exit-on-eof", no_argument,       NULL, 'e' },
                { "squeeze",     no_argument,       NULL, 's' },
                { "plain",       no_argument,       NULL, 'u' },
                { "lines",       required_argument, NULL, 'n' },
                { "version",     no_argument,       NULL, 'V' },
                { "help",        no_argument,       NULL, 'h' },
                { NULL, 0, NULL, 0 }
        };

        /* Take care of number option and +args. */
        for (opt = 0; opt < as_argc; opt++) {
                int move = 0;

                if (as_argv[opt][0] == '-' && isdigit_string(as_argv[opt] + 1)) {
                        ctl->lines_per_screen =
                            strtos16_or_err(as_argv[opt], _("failed to parse number"));
                        ctl->lines_per_screen = abs(ctl->lines_per_screen);
                        move = 1;
                } else if (as_argv[opt][0] == '+') {
                        if (isdigit_string(as_argv[opt] + 1)) {
                                ctl->next_jump = strtos32_or_err(as_argv[opt],
                                    _("failed to parse number")) - 1;
                                move = 1;
                        } else if (as_argv[opt][1] == '/') {
                                free(ctl->next_search);
                                ctl->next_search = xstrdup(as_argv[opt] + 2);
                                ctl->search_at_start = 1;
                                move = 1;
                        }
                }
                if (move) {
                        as_argc = remove_entry(as_argv, opt, as_argc);
                        opt--;
                }
        }

        while ((c = getopt_long(as_argc, as_argv, "dflcpsun:eVh", longopts, NULL)) != -1) {
                switch (c) {
                case 'd':
                        ctl->suppress_bell = 1;
                        break;
                case 'l':
                        ctl->stop_after_formfeed = 0;
                        break;
                case 'f':
                        ctl->fold_long_lines = 0;
                        break;
                case 'p':
                        ctl->no_scroll = 1;
                        break;
                case 'c':
                        ctl->clear_line_ends = 1;
                        break;
                case 's':
                        ctl->squeeze_spaces = 1;
                        break;
                case 'u':
                        break;
                case 'n':
                        ctl->lines_per_screen = strtou16_or_err(optarg, _("argument error"));
                        break;
                case 'e':
                        ctl->exit_on_eof = 1;
                        break;
                case 'V':
                        print_version(EXIT_SUCCESS);
                case 'h':
                        usage();
                default:
                        errtryhelp(EXIT_FAILURE);
                        break;
                }
        }
        ctl->num_files = as_argc - optind;
        ctl->file_names = as_argv + optind;
}

static void env_argscan(struct more_control *ctl, const char *s)
{
        char **env_argv;
        int env_argc = 1;
        int size = 8;
        const char delim[] = { ' ', '\n', '\t', '\0' };
        char *str = xstrdup(s);
        char *key = NULL, *tok;

        env_argv = xreallocarray(NULL, size, sizeof(char *));
        env_argv[0] = _("MORE environment variable");   /* program name */
        for (tok = strtok_r(str, delim, &key); tok; tok = strtok_r(NULL, delim, &key)) {
                if (size == env_argc) {
                        size *= 2;
                        env_argv = xreallocarray(env_argv, size, sizeof(char *));
                }
                env_argv[env_argc++] = tok;
        }

        argscan(ctl, env_argc, env_argv);
        /* Reset optind, command line parsing needs this.  */
        optind = 0;
        free(str);
        free(env_argv);
}

static void more_fseek(struct more_control *ctl, off_t pos)
{
        ctl->file_position = pos;
        fseeko(ctl->current_file, pos, SEEK_SET);
}

static int more_getc(struct more_control *ctl)
{
        int ret = getc(ctl->current_file);
        ctl->file_position = ftello(ctl->current_file);
        return ret;
}

static int more_ungetc(struct more_control *ctl, int c)
{
        int ret = ungetc(c, ctl->current_file);
        ctl->file_position = ftello(ctl->current_file);
        return ret;
}

static void print_separator(const int c, int n)
{
        while (n--)
                putchar(c);
        putchar('\n');
}

/* check_magic -- check for file magic numbers. */
static int check_magic(struct more_control *ctl, char *fs)
{
#ifdef HAVE_MAGIC
        const int fd = fileno(ctl->current_file);
        const char *mime_encoding = magic_descriptor(ctl->magic, fd);
        const char *magic_error_msg = magic_error(ctl->magic);

        if (magic_error_msg) {
                printf("%s: %s: %s\n", program_invocation_short_name,
                        _("magic failed"), magic_error_msg);
                return 0;
        }
        if (!mime_encoding || !(strcmp("binary", mime_encoding))) {
                printf(_("\n******** %s: Not a text file ********\n\n"), fs);
                return 1;
        }
#else
        signed char twobytes[2];

        /* don't try to look ahead if the input is unseekable */
        if (fseek(ctl->current_file, 0L, SEEK_SET))
                return 0;

        if (fread(twobytes, 2, 1, ctl->current_file) == 1) {
                switch (twobytes[0] + (twobytes[1] << 8)) {
                case 0407:      /* a.out obj */
                case 0410:      /* a.out exec */
                case 0413:      /* a.out demand exec */
                case 0405:
                case 0411:
                case 0177545:
                case 0x457f:    /* simple ELF detection */
                        printf(_("\n******** %s: Not a text file ********\n\n"),
                               fs);
                        return 1;
                }
        }
        fseek(ctl->current_file, 0L, SEEK_SET); /* rewind() not necessary */
#endif
        return 0;
}

/* Check whether the file named by fs is an ASCII file which the user may
 * access.  If it is, return the opened file.  Otherwise return NULL. */
static void checkf(struct more_control *ctl, char *fs)
{
        struct stat st;
        int c;

        ctl->current_line = 0;
        ctl->file_position = 0;
        ctl->file_size = 0;
        fflush(NULL);

        ctl->current_file = fopen(fs, "r");
        if (ctl->current_file == NULL) {
                if (ctl->clear_line_ends)
                        putp(ctl->erase_line);
                warn(_("cannot open %s"), fs);
                return;
        }
        if (fstat(fileno(ctl->current_file), &st) != 0) {
                warn(_("stat of %s failed"), fs);
                return;
        }
        if ((st.st_mode & S_IFMT) == S_IFDIR) {
                printf(_("\n*** %s: directory ***\n\n"), fs);
                ctl->current_file = NULL;
                return;
        }
        ctl->file_size = st.st_size;
        if (0 < ctl->file_size && check_magic(ctl, fs)) {
                fclose(ctl->current_file);
                ctl->current_file = NULL;
                return;
        }
        fcntl(fileno(ctl->current_file), F_SETFD, FD_CLOEXEC);
        c = more_getc(ctl);
        ctl->clear_first = (c == '\f');
        more_ungetc(ctl, c);
}

static void prepare_line_buffer(struct more_control *ctl)
{
        size_t sz = ctl->num_columns * 4;

        if (ctl->line_sz >= sz)
                return;

        if (sz < MIN_LINE_SZ)
                sz = MIN_LINE_SZ;

        /* alloc sz and extra space for \n\0 */
        ctl->line_buf = xrealloc(ctl->line_buf, sz + 2);
        ctl->line_sz = sz;
}

/* Get a logical line */
static int get_line(struct more_control *ctl, int *length)
{
        int c;
        char *p;
        int column;
        static int column_wrap;

#ifdef HAVE_WIDECHAR
        size_t i;
        wchar_t wc;
        int wc_width;
        mbstate_t state, state_bak;     /* Current status of the stream. */
        char mbc[MB_LEN_MAX];           /* Buffer for one multibyte char. */
        size_t mblength;                /* Byte length of multibyte char. */
        size_t mbc_pos = 0;             /* Position of the MBC. */
        int use_mbc_buffer_flag = 0;    /* If 1, mbc has data. */
        int break_flag = 0;             /* If 1, exit while(). */
        off_t file_position_bak = ctl->file_position;

        memset(&state, '\0', sizeof(mbstate_t));
#endif

        p = ctl->line_buf;
        column = 0;
        c = more_getc(ctl);
        if (column_wrap && c == '\n') {
                ctl->current_line++;
                c = more_getc(ctl);
        }
        while (p < &ctl->line_buf[ctl->line_sz - 1]) {
#ifdef HAVE_WIDECHAR
                if (ctl->fold_long_lines && use_mbc_buffer_flag && MB_CUR_MAX > 1) {
                        use_mbc_buffer_flag = 0;
                        state_bak = state;
                        mbc[mbc_pos++] = c;
 process_mbc:
                        mblength = mbrtowc(&wc, mbc, mbc_pos, &state);

                        switch (mblength) {
                        case (size_t)-2:        /* Incomplete multibyte character. */
                                use_mbc_buffer_flag = 1;
                                state = state_bak;
                                break;

                        case (size_t)-1:        /* Invalid as a multibyte character. */
                                *p++ = mbc[0];
                                state = state_bak;
                                column++;
                                file_position_bak++;
                                if (column >= ctl->num_columns) {
                                        more_fseek(ctl, file_position_bak);
                                } else {
                                        memmove(mbc, mbc + 1, --mbc_pos);
                                        if (mbc_pos > 0) {
                                                mbc[mbc_pos] = '\0';
                                                goto process_mbc;
                                        }
                                }
                                break;

                        default:
                                wc_width = wcwidth(wc);
                                if (column + wc_width > ctl->num_columns) {
                                        more_fseek(ctl, file_position_bak);
                                        break_flag = 1;
                                } else {
                                        for (i = 0; p < &ctl->line_buf[ctl->line_sz - 1] &&
                                                    i < mbc_pos; i++)
                                                *p++ = mbc[i];
                                        if (wc_width > 0)
                                                column += wc_width;
                                }
                        }

                        if (break_flag || column >= ctl->num_columns)
                                break;

                        c = more_getc(ctl);
                        continue;
                }
#endif  /* HAVE_WIDECHAR */
                if (c == EOF) {
                        if (p > ctl->line_buf) {
                                *p = '\0';
                                *length = p - ctl->line_buf;
                                return column;
                        }
                        *length = p - ctl->line_buf;
                        return EOF;
                }
                if (c == '\n') {
                        ctl->current_line++;
                        break;
                }

                *p++ = c;
                if (c == '\t') {
                        if (!ctl->hard_tabs || (column < ctl->prompt_len && !ctl->hard_tty)) {
                                if (ctl->hard_tabs && ctl->erase_line && !ctl->dumb_tty) {
                                        column = 1 + (column | 7);
                                        putp(ctl->erase_line);
                                        ctl->prompt_len = 0;
                                } else {
                                        for (--p; p < &ctl->line_buf[ctl->line_sz - 1];) {
                                                *p++ = ' ';
                                                if ((++column & 7) == 0)
                                                        break;
                                        }
                                        if (column >= ctl->prompt_len)
                                                ctl->prompt_len = 0;
                                }
                        } else
                                column = 1 + (column | 7);
                } else if (c == '\b' && column > 0) {
                        column--;
                } else if (c == '\r') {
                        int next = more_getc(ctl);
                        if (next == '\n') {
                                p--;
                                ctl->current_line++;
                                break;
                        }
                        more_ungetc(ctl, c);
                        column = 0;
                } else if (c == '\f' && ctl->stop_after_formfeed) {
                        p[-1] = '^';
                        *p++ = 'L';
                        column += 2;
                        ctl->is_paused = 1;
                } else if (c == EOF) {
                        *length = p - ctl->line_buf;
                        return column;
                } else {
#ifdef HAVE_WIDECHAR
                        if (ctl->fold_long_lines && MB_CUR_MAX > 1) {
                                memset(mbc, '\0', MB_LEN_MAX);
                                mbc_pos = 0;
                                mbc[mbc_pos++] = c;
                                state_bak = state;

                                mblength = mbrtowc(&wc, mbc, mbc_pos, &state);
                                /* The value of mblength is always less than 2 here. */
                                switch (mblength) {
                                case (size_t)-2:
                                        p--;
                                        file_position_bak = ctl->file_position - 1;
                                        state = state_bak;
                                        use_mbc_buffer_flag = 1;
                                        break;

                                case (size_t)-1:
                                        state = state_bak;
                                        column++;
                                        break;

                                default:
                                        wc_width = wcwidth(wc);
                                        if (wc_width > 0)
                                                column += wc_width;
                                }
                        } else
#endif  /* HAVE_WIDECHAR */
                        {
                                if (isprint(c))
                                        column++;
                        }
                }

                if (column >= ctl->num_columns && ctl->fold_long_lines)
                        break;
#ifdef HAVE_WIDECHAR
                if (use_mbc_buffer_flag == 0 && p >= &ctl->line_buf[ctl->line_sz - 1 - 4])
                        /* don't read another char if there is no space for
                         * whole multibyte sequence */
                        break;
#endif
                c = more_getc(ctl);
        }
        if (column >= ctl->num_columns && ctl->num_columns > 0) {
                if (!ctl->wrap_margin) {
                        *p++ = '\n';
                }
        }
        column_wrap = column == ctl->num_columns && ctl->fold_long_lines;
        if (column_wrap && ctl->eat_newline && ctl->wrap_margin) {
                *p++ = '\n';    /* simulate normal wrap */
        }
        *length = p - ctl->line_buf;
        *p = 0;
        return column;
}

/* Erase the rest of the prompt, assuming we are starting at column col. */
static void erase_to_col(struct more_control *ctl, int col)
{

        if (ctl->prompt_len == 0)
                return;
        if (col == 0 && ctl->clear_line_ends)
                puts(ctl->erase_line);
        else if (ctl->hard_tty)
                putchar('\n');
        else {
                if (col == 0)
                        putchar('\r');
                if (!ctl->dumb_tty && ctl->erase_line)
                        putp(ctl->erase_line);
                else {
                        printf("%*s", ctl->prompt_len - col, "");
                        if (col == 0)
                                putchar('\r');
                }
        }
        ctl->prompt_len = col;
}

static void output_prompt(struct more_control *ctl, char *filename)
{
        if (ctl->clear_line_ends)
                putp(ctl->erase_line);
        else if (ctl->prompt_len > 0)
                erase_to_col(ctl, 0);
        if (!ctl->hard_tty) {
                ctl->prompt_len = 0;
                if (ctl->enter_std) {
                        putp(ctl->enter_std);
                        ctl->prompt_len += (2 * ctl->stdout_glitch);
                }
                if (ctl->clear_line_ends)
                        putp(ctl->erase_line);
                ctl->prompt_len += printf(_("--More--"));
                if (filename != NULL) {
                        ctl->prompt_len += printf(_("(Next file: %s)"), filename);
                } else if (!ctl->no_tty_in && 0 < ctl->file_size) {
                    int position = ((ctl->file_position * 100) / ctl->file_size);
                    if (position == 100) {
                        erase_to_col(ctl, 0);
                        ctl->prompt_len += printf(_("(END)"));
                    } else {
                        ctl->prompt_len += printf("(%d%%)", position);
                    }
                } else if (ctl->is_eof) {
                        erase_to_col(ctl, 0);
                        ctl->prompt_len += printf(_("(END)"));
                }

                if (ctl->suppress_bell) {
                        ctl->prompt_len +=
                            printf(_("[Press space to continue, 'q' to quit.]"));
                }
                if (ctl->exit_std)
                        putp(ctl->exit_std);
                if (ctl->clear_line_ends)
                        putp(ctl->clear_rest);
        } else
                fprintf(stderr, "\a");
        fflush(NULL);
}

static void reset_tty(struct more_control *ctl)
{
        if (ctl->no_tty_out)
                return;
        fflush(NULL);
        ctl->output_tty.c_lflag |= ICANON | ECHO;
        ctl->output_tty.c_cc[VMIN] = ctl->original_tty.c_cc[VMIN];
        ctl->output_tty.c_cc[VTIME] = ctl->original_tty.c_cc[VTIME];
        tcsetattr(STDERR_FILENO, TCSANOW, &ctl->original_tty);
}

/* Clean up terminal state and exit. Also come here if interrupt signal received */
static void __attribute__((__noreturn__)) more_exit(struct more_control *ctl)
{
#ifdef HAVE_MAGIC
        magic_close(ctl->magic);
#endif
        reset_tty(ctl);
        if (ctl->clear_line_ends) {
                putchar('\r');
                putp(ctl->erase_line);
        } else if (!ctl->clear_line_ends && (ctl->prompt_len > 0))
                erase_to_col(ctl, 0);
        fflush(NULL);
        free(ctl->previous_search);
        free(ctl->shell_line);
        free(ctl->line_buf);
        free(ctl->go_home);
        if (ctl->current_file)
                fclose(ctl->current_file);
        del_curterm(cur_term);
        _exit(EXIT_SUCCESS);
}

static cc_t read_user_input(struct more_control *ctl)
{
        cc_t c;

        errno = 0;
        /*
         * Key commands can be read() from either stderr or stdin.  If they
         * are read from stdin such as 'cat file.txt | more' then the pipe
         * input is understood as series key commands - and that is not
         * wanted.  Keep the read() reading from stderr.
         */
        if (read(STDERR_FILENO, &c, 1) <= 0) {
                if (errno != EINTR)
                        more_exit(ctl);
                else
                        c = ctl->output_tty.c_cc[VKILL];
        }
        return c;
}

/* Read a number and command from the terminal.  Set cmd to the non-digit
 * which terminates the number. */
static struct number_command read_command(struct more_control *ctl)
{
        cc_t input[8] = { 0 };
        ssize_t i, ilen;
        struct number_command cmd = { .key = more_kc_unknown_command };

        /* See stderr note in read_user_input() */
        if ((ilen = read(STDERR_FILENO, &input, sizeof(input))) <= 0)
                return cmd;
        if (2 < ilen) {
                if (!memcmp(input, ARROW_UP, sizeof(ARROW_UP))) {
                        cmd.key = more_kc_backwards;
                        return cmd;
                } else if (!memcmp(input, ARROW_DOWN, sizeof(ARROW_DOWN))) {
                        cmd.key = more_kc_jump_lines_per_screen;
                        return cmd;
                } else if (!memcmp(input, PAGE_UP, sizeof(PAGE_UP))) {
                        cmd.key = more_kc_backwards;
                        return cmd;
                } else if (!memcmp(input, PAGE_DOWN, sizeof(PAGE_DOWN))) {
                        cmd.key = more_kc_jump_lines_per_screen;
                        return cmd;
                }
        }
        for (i = 0; i < ilen; i++) {
                if (isdigit(input[i])) {
                        if (0 < ctl->reading_num) {
                                ctl->leading_number *= 10;
                                ctl->leading_number += input[i] - '0';
                        } else
                                ctl->leading_number = input[i] - '0';
                        ctl->reading_num = 1;
                        continue;
                }
                cmd.number = ctl->leading_number;
                ctl->reading_num = 0;
                ctl->leading_number = 0;
                if (ctl->leading_colon) {
                        ctl->leading_colon = 0;
                        switch (input[i]) {
                        case 'f':
                                cmd.key = more_kc_display_file_and_line;
                                return cmd;
                        case 'n':
                                cmd.key = more_kc_next_file;
                                return cmd;
                        case 'p':
                                cmd.key = more_kc_previous_file;
                                return cmd;
                        default:
                                cmd.key = more_kc_unknown_command;
                                return cmd;
                        }
                }
                /* command is a single char */
                switch (input[i]) {
                case '.':
                        cmd.key = more_kc_repeat_previous;
                        break;
                case ':':
                        ctl->leading_colon = 1;
                        break;
                case 'b':
                case CTRL('B'):
                        cmd.key = more_kc_backwards;
                        break;
                case ' ':
                        cmd.key = more_kc_jump_lines_per_screen;
                        break;
                case 'z':
                        cmd.key = more_kc_set_lines_per_screen;
                        break;
                case 'd':
                case CTRL('D'):
                        cmd.key = more_kc_set_scroll_len;
                        break;
                case 'q':
                case 'Q':
                        cmd.key = more_kc_quit;
                        return cmd;
                        break;
                case 'f':
                case CTRL('F'):
                        cmd.key = more_kc_skip_forward_screen;
                        break;
                case 's':
                        cmd.key = more_kc_skip_forward_line;
                        break;
                case '\n':
                        cmd.key = more_kc_next_line;
                        break;
                case '\f':
                        cmd.key = more_kc_clear_screen;
                        break;
                case '\'':
                        cmd.key = more_kc_previous_search_match;
                        break;
                case '=':
                        cmd.key = more_kc_display_line;
                        break;
                case 'n':
                        cmd.key = more_kc_repeat_search;
                        break;
                case '/':
                        cmd.key = more_kc_search;
                        break;
                case '!':
                        cmd.key = more_kc_run_shell;
                        break;
                case '?':
                case 'h':
                        cmd.key = more_kc_help;
                        break;
                case 'v':
                        cmd.key = more_kc_run_editor;
                        break;
                }
        }
        return cmd;
}

/* Change displayed file from command line list to next nskip, where nskip
 * is relative position in argv and can be negative, that is a previous
 * file.  */
static void change_file(struct more_control *ctl, int nskip)
{
        if (nskip == 0)
                return;
        if (nskip > 0) {
                if (ctl->argv_position + nskip > ctl->num_files - 1)
                        nskip = ctl->num_files - ctl->argv_position - 1;
        }
        ctl->argv_position += nskip;
        if (ctl->argv_position < 0)
                ctl->argv_position = 0;
        puts(_("\n...Skipping "));
        if (ctl->clear_line_ends)
                putp(ctl->erase_line);
        if (nskip > 0)
                fputs(_("...Skipping to file "), stdout);
        else
                fputs(_("...Skipping back to file "), stdout);
        puts(ctl->file_names[ctl->argv_position]);
        if (ctl->clear_line_ends)
                putp(ctl->erase_line);
        putchar('\n');
        ctl->argv_position--;
}

static void show(struct more_control *ctl, char c)
{
        if ((c < ' ' && c != '\n' && c != ESC) || c == CERASE) {
                c += (c == CERASE) ? -0100 : 0100;
                fputs(CARAT, stderr);
                ctl->prompt_len++;
        }
        fputc(c, stderr);
        ctl->prompt_len++;
}

static void more_error(struct more_control *ctl, char *mess)
{
        if (ctl->clear_line_ends)
                putp(ctl->erase_line);
        else
                erase_to_col(ctl, 0);
        ctl->prompt_len += strlen(mess);
        if (ctl->enter_std)
                putp(ctl->enter_std);
        fputs(mess, stdout);
        if (ctl->exit_std)
                putp(ctl->exit_std);
        fflush(NULL);
        ctl->report_errors++;
}

static void erase_one_column(struct more_control *ctl)
{
        if (ctl->erase_previous_ok)
                fprintf(stderr, "%s ", ctl->backspace_ch);
        fputs(ctl->backspace_ch, stderr);
}

static void ttyin(struct more_control *ctl, char buf[], int nmax, char pchar)
{
        char *sp;
        cc_t c;
        int slash = 0;
        int maxlen;

        sp = buf;
        maxlen = 0;
        while (sp - buf < nmax) {
                if (ctl->prompt_len > maxlen)
                        maxlen = ctl->prompt_len;
                c = read_user_input(ctl);
                if (c == '\\') {
                        slash++;
                } else if (c == ctl->output_tty.c_cc[VERASE] && !slash) {
                        if (sp > buf) {
#ifdef HAVE_WIDECHAR
                                if (MB_CUR_MAX > 1) {
                                        wchar_t wc;
                                        size_t pos = 0, mblength;
                                        mbstate_t state, state_bak;

                                        memset(&state, '\0', sizeof(mbstate_t));

                                        while (1) {
                                                state_bak = state;
                                                mblength =
                                                    mbrtowc(&wc, buf + pos,
                                                            sp - buf, &state);

                                                switch (mblength) {
                                                case (size_t)-2:
                                                case (size_t)-1:
                                                        state = state_bak;
                                                        /* fallthrough */
                                                case 0:
                                                        mblength = 1;
                                                }
                                                if (buf + pos + mblength >= sp)
                                                        break;

                                                pos += mblength;
                                        }

                                        if (mblength == 1) {
                                                erase_one_column(ctl);
                                        } else {
                                                int wc_width;
                                                wc_width = wcwidth(wc);
                                                wc_width =
                                                    (wc_width <
                                                     1) ? 1 : wc_width;
                                                while (wc_width--) {
                                                        erase_one_column(ctl);
                                                }
                                        }

                                        while (mblength--) {
                                                --ctl->prompt_len;
                                                --sp;
                                        }
                                } else
#endif  /* HAVE_WIDECHAR */
                                {
                                        --ctl->prompt_len;
                                        erase_one_column(ctl);
                                        --sp;
                                }

                                if ((*sp < ' ' && *sp != '\n') || *sp == CERASE) {
                                        --ctl->prompt_len;
                                        erase_one_column(ctl);
                                }
                                continue;
                        }
                        if (!ctl->erase_line)
                                ctl->prompt_len = maxlen;
                } else if (c == ctl->output_tty.c_cc[VKILL] && !slash) {
                        if (ctl->hard_tty) {
                                show(ctl, c);
                                putchar('\n');
                                putchar(pchar);
                        } else {
                                putchar('\r');
                                putchar(pchar);
                                if (ctl->erase_line)
                                        erase_to_col(ctl, 1);
                                else if (ctl->erase_input_ok)
                                        while (ctl->prompt_len-- > 1)
                                                fprintf(stderr, "%s %s", ctl->backspace_ch, ctl->backspace_ch);
                                ctl->prompt_len = 1;
                        }
                        sp = buf;
                        fflush(NULL);
                        continue;
                }
                if (slash && (c == ctl->output_tty.c_cc[VKILL] ||
                              c == ctl->output_tty.c_cc[VERASE])) {
                        erase_one_column(ctl);
                        --sp;
                }
                if (c != '\\')
                        slash = 0;
                *sp++ = c;
                if ((c < ' ' && c != '\n' && c != ESC) || c == CERASE) {
                        c += (c == CERASE) ? -0100 : 0100;
                        fputs(CARAT, stderr);
                        ctl->prompt_len++;
                }
                if (c != '\n' && c != ESC) {
                        fputc(c, stderr);
                        ctl->prompt_len++;
                } else
                        break;
        }
        *--sp = '\0';
        if (!ctl->erase_line)
                ctl->prompt_len = maxlen;
        if (sp - buf >= nmax - 1)
                more_error(ctl, _("Line too long"));
}

/* Expand shell command line. */
static void expand(struct more_control *ctl, char *inbuf)
{
        char *inpstr;
        char *outstr;
        char c;
        char *temp;
        int tempsz, xtra = 0, offset;

        if (!ctl->no_tty_in)
                xtra += strlen(ctl->file_names[ctl->argv_position]) + 1;
        if (ctl->shell_line)
                xtra += strlen(ctl->shell_line) + 1;

        tempsz = COMMAND_BUF + xtra;
        temp = xmalloc(tempsz);
        inpstr = inbuf;
        outstr = temp;

        while ((c = *inpstr++) != '\0') {
                offset = outstr - temp;
                if (tempsz - offset - 1 < xtra) {
                        tempsz += COMMAND_BUF + xtra;
                        temp = xrealloc(temp, tempsz);
                        outstr = temp + offset;
                }
                switch (c) {
                case '%':
                        if (!ctl->no_tty_in) {
                                strcpy(outstr, ctl->file_names[ctl->argv_position]);
                                outstr += strlen(ctl->file_names[ctl->argv_position]);
                        } else
                                *outstr++ = c;
                        break;
                case '!':
                        if (ctl->shell_line) {
                                strcpy(outstr, ctl->shell_line);
                                outstr += strlen(ctl->shell_line);
                        } else
                                more_error(ctl, _
                                           ("No previous command to substitute for"));
                        break;
                case '\\':
                        if (*inpstr == '%' || *inpstr == '!') {
                                *outstr++ = *inpstr++;
                                break;
                        }
                        /* fallthrough */
                default:
                        *outstr++ = c;
                }
        }
        *outstr++ = '\0';
        free(ctl->shell_line);
        ctl->shell_line = temp;
}

static void set_tty(struct more_control *ctl)
{
        ctl->output_tty.c_lflag &= ~(ICANON | ECHO);
        ctl->output_tty.c_cc[VMIN] = 1; /* read at least 1 char */
        ctl->output_tty.c_cc[VTIME] = 0;        /* no timeout */
        tcsetattr(STDERR_FILENO, TCSANOW, &ctl->output_tty);
}

/* Come here if a quit signal is received */
static void sigquit_handler(struct more_control *ctl)
{
        if (!ctl->dumb_tty && ctl->no_quit_dialog) {
                ctl->prompt_len += fprintf(stderr, _("[Use q or Q to quit]"));
                ctl->no_quit_dialog = 0;
        } else
                more_exit(ctl);
}

/* Come here when we get a suspend signal from the terminal */
static void sigtstp_handler(struct more_control *ctl)
{
        reset_tty(ctl);
        fflush(NULL);
        kill(getpid(), SIGSTOP);
}

/* Come here when we get a continue signal from the terminal */
static void sigcont_handler(struct more_control *ctl)
{
        set_tty(ctl);
}

/* Come here if a signal for a window size change is received */
static void sigwinch_handler(struct more_control *ctl)
{
        struct winsize win;

        if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &win) != -1) {
                if (win.ws_row != 0) {
                        ctl->lines_per_page = win.ws_row;
                        ctl->d_scroll_len = ctl->lines_per_page / 2 - 1;
                        if (ctl->d_scroll_len < 1)
                                ctl->d_scroll_len = 1;
                        ctl->lines_per_screen = ctl->lines_per_page - 1;
                }
                if (win.ws_col != 0)
                        ctl->num_columns = win.ws_col;
        }
        prepare_line_buffer(ctl);
}

static void __attribute__((__format__ (__printf__, 3, 4)))
        execute(struct more_control *ctl, char *filename, const char *cmd, ...)
{
        pid_t id;
        va_list argp;
        char *arg;
        char **args;
        int argcount;

        fflush(NULL);
        id = fork();
        if (id == 0) {
                int errsv;
                if (!isatty(STDIN_FILENO)) {
                        close(STDIN_FILENO);
                        ignore_result( open("/dev/tty", 0) );
                }
                reset_tty(ctl);

                va_start(argp, cmd);
                arg = va_arg(argp, char *);
                argcount = 0;
                while (arg) {
                        argcount++;
                        arg = va_arg(argp, char *);
                }
                va_end(argp);

                args = xcalloc(argcount + 1, sizeof(char *));

                va_start(argp, cmd);
                arg = va_arg(argp, char *);
                argcount = 0;
                while (arg) {
                        args[argcount] = arg;
                        argcount++;
                        arg = va_arg(argp, char *);
                }
                va_end(argp);

                if ((geteuid() != getuid() || getegid() != getgid())
                    && drop_permissions() != 0)
                        err(EXIT_FAILURE, _("drop permissions failed"));

                execvp(cmd, args);
                errsv = errno;
                fputs(_("exec failed\n"), stderr);
                exit(errsv == ENOENT ? EX_EXEC_ENOENT : EX_EXEC_FAILED);
        }
        if (id > 0) {
                errno = 0;
                while (wait(NULL) > 0) {
                        if (errno == EINTR)
                                continue;
                }
        } else
                fputs(_("can't fork\n"), stderr);
        set_tty(ctl);
        print_separator('-', 24);
        output_prompt(ctl, filename);
}

static void run_shell(struct more_control *ctl, char *filename)
{
        char cmdbuf[COMMAND_BUF];

        erase_to_col(ctl, 0);
        putchar('!');
        fflush(NULL);
        if (ctl->previous_command.key == more_kc_run_shell && ctl->shell_line)
                fputs(ctl->shell_line, stderr);
        else {
                ttyin(ctl, cmdbuf, sizeof(cmdbuf) - 2, '!');
                if (strpbrk(cmdbuf, "%!\\"))
                        expand(ctl, cmdbuf);
                else {
                        free(ctl->shell_line);
                        ctl->shell_line = xstrdup(cmdbuf);
                }
        }
        fputc('\n', stderr);
        fflush(NULL);
        ctl->prompt_len = 0;
        execute(ctl, filename, ctl->shell, ctl->shell, "-c", ctl->shell_line, 0);
}

/* Skip n lines in the file f */
static void skip_lines(struct more_control *ctl)
{
        int c;

        while (ctl->next_jump > 0) {
                while ((c = more_getc(ctl)) != '\n')
                        if (c == EOF)
                                return;
                ctl->next_jump--;
                ctl->current_line++;
        }
}

/*  Clear the screen */
static void more_clear_screen(struct more_control *ctl)
{
        if (ctl->clear && !ctl->hard_tty) {
                putp(ctl->clear);
                /* Put out carriage return so that system doesn't get
                 * confused by escape sequences when expanding tabs */
                putchar('\r');
                ctl->prompt_len = 0;
        }
}

static void read_line(struct more_control *ctl)
{
        int c;
        char *p;

        p = ctl->line_buf;
        while ((c = more_getc(ctl)) != '\n' && c != EOF
               && (ptrdiff_t)p != (ptrdiff_t)(ctl->line_buf + ctl->line_sz - 1))
                *p++ = c;
        if (c == '\n')
                ctl->current_line++;
        *p = '\0';
}

static int more_poll(struct more_control *ctl, int timeout)
{
        struct pollfd pfd[2];

        pfd[0].fd = ctl->sigfd;
        pfd[0].events = POLLIN | POLLERR | POLLHUP;
        pfd[1].fd = STDIN_FILENO;
        pfd[1].events = POLLIN;

        if (poll(pfd, 2, timeout) < 0) {
                if (errno == EAGAIN)
                        return 1;
                more_error(ctl, _("poll failed"));
                return 1;
        }
        if (pfd[0].revents != 0) {
                struct signalfd_siginfo info;
                ssize_t sz;

                sz = read(pfd[0].fd, &info, sizeof(info));
                assert(sz == sizeof(info));
                switch (info.ssi_signo) {
                case SIGINT:
                        more_exit(ctl);
                        break;
                case SIGQUIT:
                        sigquit_handler(ctl);
                        break;
                case SIGTSTP:
                        sigtstp_handler(ctl);
                        break;
                case SIGCONT:
                        sigcont_handler(ctl);
                        break;
                case SIGWINCH:
                        sigwinch_handler(ctl);
                        break;
                default:
                        abort();
                }
        }
        if (pfd[1].revents == 0)
                return 1;
        return 0;
}

/* Search for nth occurrence of regular expression contained in buf in
 * the file */
static void search(struct more_control *ctl, char buf[], int n)
{
        off_t startline = ctl->file_position;
        off_t line1 = startline;
        off_t line2 = startline;
        off_t line3;
        int lncount;
        int saveln, rc;
        regex_t re;

        if (buf != ctl->previous_search) {
                free(ctl->previous_search);
                ctl->previous_search = buf;
        }

        ctl->search_called = 1;
        ctl->context.line_num = saveln = ctl->current_line;
        ctl->context.row_num = startline;
        lncount = 0;
        if (!buf)
                goto notfound;
        if ((rc = regcomp(&re, buf, REG_NOSUB)) != 0) {
                char s[REGERR_BUF];
                regerror(rc, &re, s, sizeof s);
                more_error(ctl, s);
                return;
        }
        while (!feof(ctl->current_file)) {
                line3 = line2;
                line2 = line1;
                line1 = ctl->file_position;
                read_line(ctl);
                lncount++;
                if (regexec(&re, ctl->line_buf, 0, NULL, 0) == 0 && --n == 0) {
                        if ((1 < lncount && ctl->no_tty_in) || 3 < lncount) {
                                putchar('\n');
                                if (ctl->clear_line_ends)
                                        putp(ctl->erase_line);
                                fputs(_("...skipping\n"), stdout);
                        }
                        if (!ctl->no_tty_in) {
                                ctl->current_line -= (lncount < 3 ? lncount : 3);
                                more_fseek(ctl, line3);
                                if (ctl->no_scroll) {
                                        if (ctl->clear_line_ends) {
                                                putp(ctl->go_home);
                                                putp(ctl->erase_line);
                                        } else
                                                more_clear_screen(ctl);
                                }
                        } else {
                                erase_to_col(ctl, 0);
                                if (ctl->no_scroll) {
                                        if (ctl->clear_line_ends) {
                                                putp(ctl->go_home);
                                                putp(ctl->erase_line);
                                        } else
                                                more_clear_screen(ctl);
                                }
                                puts(ctl->line_buf);
                        }
                        break;
                }
                more_poll(ctl, 1);
        }
        /* Move ctrl+c signal handling back to more_key_command(). */
        signal(SIGINT, SIG_DFL);
        sigaddset(&ctl->sigset, SIGINT);
        sigprocmask(SIG_BLOCK, &ctl->sigset, NULL);
        regfree(&re);
        if (feof(ctl->current_file)) {
                if (!ctl->no_tty_in) {
                        ctl->current_line = saveln;
                        more_fseek(ctl, startline);
                } else {
                        fputs(_("\nPattern not found\n"), stdout);
                        more_exit(ctl);
                }
notfound:
                more_error(ctl, _("Pattern not found"));
        }
}

static char *find_editor(void)
{
        static char *editor;

        editor = getenv("VISUAL");
        if (editor == NULL || *editor == '\0')
                editor = getenv("EDITOR");
        if (editor == NULL || *editor == '\0')
                editor = _PATH_VI;
        return editor;
}

static void runtime_usage(void)
{
        fputs(_("Most commands optionally preceded by integer argument k.  "
                "Defaults in brackets.\n"
                "Star (*) indicates argument becomes new default.\n"), stdout);
        print_separator('-', 79);
        fprintf(stdout,
                _
                ("<space>                 Display next k lines of text [current screen size]\n"
                 "z                       Display next k lines of text [current screen size]*\n"
                 "<return>                Display next k lines of text [1]*\n"
                 "d or ctrl-D             Scroll k lines [current scroll size, initially 11]*\n"
                 "q or Q or <interrupt>   Exit from more\n"
                 "s                       Skip forward k lines of text [1]\n"
                 "f                       Skip forward k screenfuls of text [1]\n"
                 "b or ctrl-B             Skip backwards k screenfuls of text [1]\n"
                 "'                       Go to place where previous search started\n"
                 "=                       Display current line number\n"
                 "/<regular expression>   Search for kth occurrence of regular expression [1]\n"
                 "n                       Search for kth occurrence of last r.e [1]\n"
                 "!<cmd> or :!<cmd>       Execute <cmd> in a subshell\n"
                 "v                       Start up '%s' at current line\n"
                 "ctrl-L                  Redraw screen\n"
                 ":n                      Go to kth next file [1]\n"
                 ":p                      Go to kth previous file [1]\n"
                 ":f                      Display current file name and line number\n"
                 ".                       Repeat previous command\n"),
                find_editor());
        print_separator('-', 79);
}

static void execute_editor(struct more_control *ctl, char *cmdbuf, size_t buflen, char *filename)
{
        char *editor, *p;
        int split = 0;
        int n;

        if ((ctl->current_line - ctl->lines_per_screen) < 1)
                n = 1;
        else
                n = ctl->current_line - (ctl->lines_per_screen + 1) / 2;
        editor = find_editor();
        p = strrchr(editor, '/');
        if (p)
                p++;
        else
                p = editor;
        /*
         * Earlier: call vi +n file. This also works for emacs.
         * POSIX: call vi -c n file (when editor is vi or ex).
         */
        if (!strcmp(p, "vi") || !strcmp(p, "ex")) {
                snprintf(cmdbuf, buflen, "-c %d", n);
                split = 1;
        } else
                snprintf(cmdbuf, buflen, "+%d", n);

        erase_to_col(ctl, 0);
        printf("%s %s %s", editor, cmdbuf, ctl->file_names[ctl->argv_position]);
        if (split) {
                cmdbuf[2] = 0;
                execute(ctl, filename, editor, editor,
                        cmdbuf, cmdbuf + 3,
                        ctl->file_names[ctl->argv_position], (char *)0);
        } else
                execute(ctl, filename, editor, editor,
                        cmdbuf, ctl->file_names[ctl->argv_position], (char *)0);
}

static int skip_backwards(struct more_control *ctl, int nlines)
{
        if (nlines == 0)
                nlines++;
        erase_to_col(ctl, 0);
        printf(P_("...back %d page", "...back %d pages", nlines), nlines);
        putchar('\n');
        ctl->next_jump = ctl->current_line - (ctl->lines_per_screen * (nlines + 1)) - 1;
        if (ctl->next_jump < 0)
                ctl->next_jump = 0;
        more_fseek(ctl, 0);
        ctl->current_line = 0;
        skip_lines(ctl);
        return ctl->lines_per_screen;
}

static int skip_forwards(struct more_control *ctl, int nlines, cc_t comchar)
{
        int c;

        if (nlines == 0)
                nlines++;
        if (comchar == 'f')
                nlines *= ctl->lines_per_screen;
        putchar('\r');
        erase_to_col(ctl, 0);
        putchar('\n');
        if (ctl->clear_line_ends)
                putp(ctl->erase_line);
        printf(P_("...skipping %d line",
                  "...skipping %d lines", nlines), nlines);

        if (ctl->clear_line_ends)
                putp(ctl->erase_line);
        putchar('\n');

        while (nlines > 0) {
                while ((c = more_getc(ctl)) != '\n')
                        if (c == EOF)
                                return 0;
                ctl->current_line++;
                nlines--;
        }
        return 1;
}

/* Read a command and do it.  A command consists of an optional integer
 * argument followed by the command character.  Return the number of
 * lines to display in the next screenful.  If there is nothing more to
 * display in the current file, zero is returned. */
static int more_key_command(struct more_control *ctl, char *filename)
{
        int retval = 0;
        int done = 0, search_again = 0;
        char cmdbuf[INIT_BUF];
        struct number_command cmd;

        if (!ctl->report_errors)
                output_prompt(ctl, filename);
        else
                ctl->report_errors = 0;
        ctl->search_called = 0;
        for (;;) {
                if (more_poll(ctl, -1) != 0)
                        continue;
                cmd = read_command(ctl);
                if (cmd.key == more_kc_unknown_command)
                        continue;
                if (cmd.key == more_kc_repeat_previous)
                        cmd = ctl->previous_command;
                switch (cmd.key) {
                case more_kc_backwards:
                        if (ctl->no_tty_in) {
                                fprintf(stderr, "\a");
                                return -1;
                        }
                        retval = skip_backwards(ctl, cmd.number);
                        done = 1;
                        break;
                case more_kc_jump_lines_per_screen:
                case more_kc_set_lines_per_screen:
                        if (cmd.number == 0)
                                cmd.number = ctl->lines_per_screen;
                        else if (cmd.key == more_kc_set_lines_per_screen)
                                ctl->lines_per_screen = cmd.number;
                        retval = cmd.number;
                        done = 1;
                        break;
                case more_kc_set_scroll_len:
                        if (cmd.number != 0)
                                ctl->d_scroll_len = cmd.number;
                        retval = ctl->d_scroll_len;
                        done = 1;
                        break;
                case more_kc_quit:
                        more_exit(ctl);
                case more_kc_skip_forward_screen:
                        if (skip_forwards(ctl, cmd.number, 'f'))
                                retval = ctl->lines_per_screen;
                        done = 1;
                        break;
                case more_kc_skip_forward_line:
                        if (skip_forwards(ctl, cmd.number, 's'))
                                retval = ctl->lines_per_screen;
                        done = 1;
                        break;
                case more_kc_next_line:
                        if (cmd.number != 0)
                                ctl->lines_per_screen = cmd.number;
                        else
                                cmd.number = 1;
                        retval = cmd.number;
                        done = 1;
                        break;
                case more_kc_clear_screen:
                        if (!ctl->no_tty_in) {
                                more_clear_screen(ctl);
                                more_fseek(ctl, ctl->screen_start.row_num);
                                ctl->current_line = ctl->screen_start.line_num;
                                retval = ctl->lines_per_screen;
                                done = 1;
                                break;
                        } else {
                                fprintf(stderr, "\a");
                                break;
                        }
                case more_kc_previous_search_match:
                        if (!ctl->no_tty_in) {
                                erase_to_col(ctl, 0);
                                fputs(_("\n***Back***\n\n"), stdout);
                                more_fseek(ctl, ctl->context.row_num);
                                ctl->current_line = ctl->context.line_num;
                                retval = ctl->lines_per_screen;
                                done = 1;
                                break;
                        } else {
                                fprintf(stderr, "\a");
                                break;
                        }
                case more_kc_display_line:
                        erase_to_col(ctl, 0);
                        ctl->prompt_len = printf("%d", ctl->current_line);
                        fflush(NULL);
                        break;
                case more_kc_display_file_and_line:
                        erase_to_col(ctl, 0);
                        if (!ctl->no_tty_in)
                                ctl->prompt_len =
                                    printf(_("\"%s\" line %d"),
                                           ctl->file_names[ctl->argv_position], ctl->current_line);
                        else
                                ctl->prompt_len = printf(_("[Not a file] line %d"),
                                                         ctl->current_line);
                        fflush(NULL);
                        break;
                case more_kc_repeat_search:
                        if (!ctl->previous_search) {
                                more_error(ctl, _("No previous regular expression"));
                                break;
                        }
                        search_again = 1;
                        /* fallthrough */
                case more_kc_search:
                        if (cmd.number == 0)
                                cmd.number++;
                        erase_to_col(ctl, 0);
                        putchar('/');
                        ctl->prompt_len = 1;
                        fflush(NULL);
                        if (search_again) {
                                fputc('\r', stderr);
                                search(ctl, ctl->previous_search, cmd.number);
                                search_again = 0;
                        } else {
                                ttyin(ctl, cmdbuf, sizeof(cmdbuf) - 2, '/');
                                fputc('\r', stderr);
                                ctl->next_search = xstrdup(cmdbuf);
                                search(ctl, ctl->next_search, cmd.number);
                        }
                        retval = ctl->lines_per_screen - 1;
                        done = 1;
                        break;
                case more_kc_run_shell:
                        run_shell(ctl, filename);
                        break;
                case more_kc_help:
                        if (ctl->no_scroll)
                                more_clear_screen(ctl);
                        erase_to_col(ctl, 0);
                        runtime_usage();
                        output_prompt(ctl, filename);
                        break;
                case more_kc_next_file:
                        putchar('\r');
                        erase_to_col(ctl, 0);
                        if (cmd.number == 0)
                                cmd.number = 1;
                        if (ctl->argv_position + cmd.number >= (unsigned int)ctl->num_files)
                                more_exit(ctl);
                        change_file(ctl, cmd.number);
                        done = 1;
                        break;
                case more_kc_previous_file:
                        if (ctl->no_tty_in) {
                                fprintf(stderr, "\a");
                                break;
                        }
                        putchar('\r');
                        erase_to_col(ctl, 0);
                        if (cmd.number == 0)
                                cmd.number = 1;
                        change_file(ctl, -cmd.number);
                        done = 1;
                        break;
                case more_kc_run_editor:        /* This case should go right before default */
                        if (!ctl->no_tty_in) {
                                execute_editor(ctl, cmdbuf, sizeof(cmdbuf), filename);
                                break;
                        }
                        /* fallthrough */
                default:
                        if (ctl->suppress_bell) {
                                erase_to_col(ctl, 0);
                                if (ctl->enter_std)
                                        putp(ctl->enter_std);
                                ctl->prompt_len =
                                    printf(_("[Press 'h' for instructions.]"))
                                            + 2 * ctl->stdout_glitch;
                                if (ctl->exit_std)
                                        putp(ctl->exit_std);
                        } else
                                fprintf(stderr, "\a");
                        fflush(NULL);
                        break;
                }
                ctl->previous_command = cmd;
                if (done) {
                        cmd.key = more_kc_unknown_command;
                        break;
                }
        }
        putchar('\r');
        ctl->no_quit_dialog = 1;
        return retval;
}

/* Print out the contents of the file f, one screenful at a time. */
static void screen(struct more_control *ctl, int num_lines)
{
        int c;
        int nchars;
        int length;                     /* length of current line */
        static int prev_len = 1;        /* length of previous line */

        for (;;) {
                while (num_lines > 0 && !ctl->is_paused) {
                        nchars = get_line(ctl, &length);
                        ctl->is_eof = nchars == EOF;
                        if (ctl->is_eof && ctl->exit_on_eof) {
                                if (ctl->clear_line_ends)
                                        putp(ctl->clear_rest);
                                return;
                        }
                        if (ctl->squeeze_spaces && length == 0 && prev_len == 0 && !ctl->is_eof)
                                continue;
                        prev_len = length;
                        if (ctl->bad_stdout
                            || ((ctl->enter_std && *ctl->enter_std == ' ') && (ctl->prompt_len > 0)))
                                erase_to_col(ctl, 0);
                        /* must clear before drawing line since tabs on
                         * some terminals do not erase what they tab
                         * over. */
                        if (ctl->clear_line_ends)
                                putp(ctl->erase_line);
                        fwrite(ctl->line_buf, length, 1, stdout);
                        if (nchars < ctl->prompt_len)
                                erase_to_col(ctl, nchars);
                        ctl->prompt_len = 0;
                        if (nchars < ctl->num_columns || !ctl->fold_long_lines)
                                putchar('\n');
                        num_lines--;
                }
                fflush(NULL);

                c = more_getc(ctl);
                ctl->is_eof = c == EOF;

                if (ctl->is_eof && ctl->exit_on_eof) {
                        if (ctl->clear_line_ends)
                                putp(ctl->clear_rest);
                        return;
                }

                if (ctl->is_paused && ctl->clear_line_ends)
                        putp(ctl->clear_rest);
                more_ungetc(ctl, c);
                ctl->is_paused = 0;
                do {
                        if ((num_lines = more_key_command(ctl, NULL)) == 0)
                                return;
                } while (ctl->search_called && !ctl->previous_search);
                if (ctl->hard_tty && ctl->prompt_len > 0)
                        erase_to_col(ctl, 0);
                if (ctl->no_scroll && num_lines >= ctl->lines_per_screen) {
                        if (ctl->clear_line_ends)
                                putp(ctl->go_home);
                        else
                                more_clear_screen(ctl);
                }
                ctl->screen_start.line_num = ctl->current_line;
                ctl->screen_start.row_num = ctl->file_position;
        }
}

static void copy_file(FILE *f)
{
        char buf[BUFSIZ];
        size_t sz;

        while ((sz = fread(&buf, sizeof(char), sizeof(buf), f)) > 0)
                fwrite(&buf, sizeof(char), sz, stdout);
}


static void display_file(struct more_control *ctl, int left)
{
        if (!ctl->current_file)
                return;
        ctl->context.line_num = ctl->context.row_num = 0;
        ctl->current_line = 0;
        if (ctl->first_file) {
                ctl->first_file = 0;
                if (ctl->next_jump)
                        skip_lines(ctl);
                if (ctl->search_at_start) {
                        search(ctl, ctl->next_search, 1);
                        if (ctl->no_scroll)
                                left--;
                }
        } else if (ctl->argv_position < ctl->num_files && !ctl->no_tty_out)
                left =
                    more_key_command(ctl, ctl->file_names[ctl->argv_position]);
        if (left != 0) {
                if ((ctl->no_scroll || ctl->clear_first)
                    && 0 < ctl->file_size) {
                        if (ctl->clear_line_ends)
                                putp(ctl->go_home);
                        else
                                more_clear_screen(ctl);
                }
                if (ctl->print_banner) {
                        if (ctl->bad_stdout)
                                erase_to_col(ctl, 0);
                        if (ctl->clear_line_ends)
                                putp(ctl->erase_line);
                        if (ctl->prompt_len > 14)
                                erase_to_col(ctl, 14);
                        if (ctl->clear_line_ends)
                                putp(ctl->erase_line);
                        print_separator(':', 14);
                        if (ctl->clear_line_ends)
                                putp(ctl->erase_line);
                        puts(ctl->file_names[ctl->argv_position]);
                        if (ctl->clear_line_ends)
                                putp(ctl->erase_line);
                        print_separator(':', 14);
                        if (left > ctl->lines_per_page - 4)
                                left = ctl->lines_per_page - 4;
                }
                if (ctl->no_tty_out)
                        copy_file(ctl->current_file);
                else
                        screen(ctl, left);
        }
        fflush(NULL);
        fclose(ctl->current_file);
        ctl->current_file = NULL;
        ctl->screen_start.line_num = ctl->screen_start.row_num = 0;
        ctl->context.line_num = ctl->context.row_num = 0L;
}

static void initterm(struct more_control *ctl)
{
        int ret;
        char *term;
        struct winsize win;
        char *cursor_addr;

#ifndef NON_INTERACTIVE_MORE
        ctl->no_tty_out = tcgetattr(STDOUT_FILENO, &ctl->output_tty);
#endif
        ctl->no_tty_in = tcgetattr(STDIN_FILENO, &ctl->output_tty);
        ctl->no_tty_err = tcgetattr(STDERR_FILENO, &ctl->output_tty);
        ctl->original_tty = ctl->output_tty;

        ctl->hard_tabs = (ctl->output_tty.c_oflag & TABDLY) != TAB3;
        if (ctl->no_tty_out)
                return;

        ctl->output_tty.c_lflag &= ~(ICANON | ECHO);
        ctl->output_tty.c_cc[VMIN] = 1;
        ctl->output_tty.c_cc[VTIME] = 0;
        ctl->erase_previous_ok = (ctl->output_tty.c_cc[VERASE] != 255);
        ctl->erase_input_ok = (ctl->output_tty.c_cc[VKILL] != 255);
        if ((term = getenv("TERM")) == NULL) {
                ctl->dumb_tty = 1;
        }
        setupterm(term, 1, &ret);
        if (ret <= 0) {
                ctl->dumb_tty = 1;
                return;
        }
        if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &win) < 0) {
                ctl->lines_per_page = tigetnum(TERM_LINES);
                ctl->num_columns = tigetnum(TERM_COLS);
        } else {
                if ((ctl->lines_per_page = win.ws_row) == 0)
                        ctl->lines_per_page = tigetnum(TERM_LINES);
                if ((ctl->num_columns = win.ws_col) == 0)
                        ctl->num_columns = tigetnum(TERM_COLS);
        }
        if ((ctl->lines_per_page <= 0) || tigetflag(TERM_HARD_COPY)) {
                ctl->hard_tty = 1;
                ctl->lines_per_page = LINES_PER_PAGE;
        }

        if (tigetflag(TERM_EAT_NEW_LINE))
                /* Eat newline at last column + 1; dec, concept */
                ctl->eat_newline++;
        if (ctl->num_columns <= 0)
                ctl->num_columns = NUM_COLUMNS;

        ctl->wrap_margin = tigetflag(TERM_AUTO_RIGHT_MARGIN);
        ctl->bad_stdout = tigetflag(TERM_CEOL);
        ctl->erase_line = tigetstr(TERM_CLEAR_TO_LINE_END);
        ctl->clear = tigetstr(TERM_CLEAR);
        if ((ctl->enter_std = tigetstr(TERM_STANDARD_MODE)) != NULL) {
                ctl->exit_std = tigetstr(TERM_EXIT_STANDARD_MODE);
                if (0 < tigetnum(TERM_STD_MODE_GLITCH))
                        ctl->stdout_glitch = 1;
        }

        cursor_addr = tigetstr(TERM_HOME);
        if (cursor_addr == NULL || *cursor_addr == '\0') {
                cursor_addr = tigetstr(TERM_CURSOR_ADDRESS);
                if (cursor_addr)
                        cursor_addr = tparm(cursor_addr, 0, 0);
        }
        if (cursor_addr)
                ctl->go_home = xstrdup(cursor_addr);

        if ((ctl->move_line_down = tigetstr(TERM_LINE_DOWN)) == NULL)
                ctl->move_line_down = BACKSPACE;
        ctl->clear_rest = tigetstr(TERM_CLEAR_TO_SCREEN_END);
        if ((ctl->backspace_ch = tigetstr(TERM_BACKSPACE)) == NULL)
                ctl->backspace_ch = BACKSPACE;

        if ((ctl->shell = getenv("SHELL")) == NULL)
                ctl->shell = _PATH_BSHELL;
}

int main(int argc, char **argv)
{
        char *s;
        int left;
        struct more_control ctl = {
                .first_file = 1,
                .fold_long_lines = 1,
                .no_quit_dialog = 1,
                .stop_after_formfeed = 1,
                .wrap_margin = 1,
                .lines_per_page = LINES_PER_PAGE,
                .num_columns = NUM_COLUMNS,
                .d_scroll_len = SCROLL_LEN,
                0
        };

        setlocale(LC_ALL, "");
        bindtextdomain(PACKAGE, LOCALEDIR);
        textdomain(PACKAGE);
        close_stdout_atexit();
        setlocale(LC_ALL, "");

        /* Auto set no scroll on when binary is called page */
        if (!(strcmp(program_invocation_short_name, "page")))
                ctl.no_scroll++;

        ctl.exit_on_eof = getenv("POSIXLY_CORRECT") ? 0 : 1;

        if ((s = getenv("MORE")) != NULL)
                env_argscan(&ctl, s);

        argscan(&ctl, argc, argv);

        /* clear any inherited settings */
        signal(SIGCHLD, SIG_DFL);

        initterm(&ctl);

        if (ctl.no_tty_err)
                /* exit when we cannot read user's input */
                ctl.exit_on_eof = 1;

#ifdef HAVE_MAGIC
        ctl.magic = magic_open(MAGIC_MIME_ENCODING | MAGIC_SYMLINK);
        magic_load(ctl.magic, NULL);
#endif
        prepare_line_buffer(&ctl);

        ctl.d_scroll_len = ctl.lines_per_page / 2 - 1;
        if (ctl.d_scroll_len <= 0)
                ctl.d_scroll_len = 1;

        /* allow clear_line_ends only if go_home and erase_line and clear_rest strings are
         * defined, and in that case, make sure we are in no_scroll mode */
        if (ctl.clear_line_ends) {
                if ((ctl.go_home == NULL) || (*ctl.go_home == '\0') ||
                    (ctl.erase_line == NULL) || (*ctl.erase_line == '\0') ||
                    (ctl.clear_rest == NULL) || (*ctl.clear_rest == '\0'))
                        ctl.clear_line_ends = 0;
                else
                        ctl.no_scroll = 1;
        }
        if (ctl.lines_per_screen == 0)
                ctl.lines_per_screen = ctl.lines_per_page - 1;
        left = ctl.lines_per_screen;
        if (ctl.num_files > 1)
                ctl.print_banner = 1;
        if (!ctl.no_tty_in && ctl.num_files == 0) {
                warnx(_("bad usage"));
                errtryhelp(EXIT_FAILURE);
        } else
                ctl.current_file = stdin;
        if (!ctl.no_tty_out) {
                if (signal(SIGTSTP, SIG_IGN) == SIG_DFL) {
                        ctl.catch_suspend++;
                }
                tcsetattr(STDERR_FILENO, TCSANOW, &ctl.output_tty);
        }
        sigemptyset(&ctl.sigset);
        sigaddset(&ctl.sigset, SIGINT);
        sigaddset(&ctl.sigset, SIGQUIT);
        sigaddset(&ctl.sigset, SIGTSTP);
        sigaddset(&ctl.sigset, SIGCONT);
        sigaddset(&ctl.sigset, SIGWINCH);
        sigprocmask(SIG_BLOCK, &ctl.sigset, NULL);
        ctl.sigfd = signalfd(-1, &ctl.sigset, SFD_CLOEXEC);
        if (ctl.no_tty_in) {
                if (ctl.no_tty_out)
                        copy_file(stdin);
                else {
                        ctl.current_file = stdin;
                        display_file(&ctl, left);
                }
                ctl.no_tty_in = 0;
                ctl.print_banner = 1;
                ctl.first_file = 0;
        }

        while (ctl.argv_position < ctl.num_files) {
                checkf(&ctl, ctl.file_names[ctl.argv_position]);
                display_file(&ctl, left);
                ctl.first_file = 0;
                ctl.argv_position++;
        }
        ctl.clear_line_ends = 0;
        ctl.prompt_len = 0;
        more_exit(&ctl);
}