hardlink: fix typo

[thirdparty/util-linux.git] / misc-utils / hardlink.c

/* hardlink.c - Link multiple identical files together
 *
 * Copyright (C) 2008 - 2014 Julian Andres Klode <jak@jak-linux.org>
 * Copyright (C) 2021 Karel Zak <kzak@redhat.com>
 *
 * SPDX-License-Identifier: MIT
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
#define _POSIX_C_SOURCE 200112L /* POSIX functions */
#define _XOPEN_SOURCE      600  /* nftw() */

#include <sys/types.h>          /* stat */
#include <sys/stat.h>           /* stat */
#include <sys/time.h>           /* getrlimit, getrusage */
#include <sys/resource.h>       /* getrlimit, getrusage */
#include <fcntl.h>              /* posix_fadvise */
#include <ftw.h>                /* ftw */
#include <search.h>             /* tsearch() and friends */
#include <signal.h>             /* SIG*, sigaction */
#include <getopt.h>             /* getopt_long() */
#include <ctype.h>              /* tolower() */

#include "nls.h"
#include "c.h"
#include "xalloc.h"
#include "strutils.h"
#include "monotonic.h"
#include "optutils.h"

/* Use libpcre2posix if it's available */
#ifdef HAVE_PCRE2_POSIX
# include <pcre2posix.h>
# undef REG_NOSUB
# define REG_NOSUB 0            /* we do want backreferences in PCRE mode */
#else
# include <regex.h>             /* regcomp(), regsearch() */
#endif

#ifdef HAVE_SYS_XATTR_H
# include <sys/xattr.h>         /* listxattr, getxattr */
#endif

static int quiet;               /* don't print anything */

/**
 * struct file - Information about a file
 * @st:       The stat buffer associated with the file
 * @next:     Next file with the same size
 * @basename: The offset off the basename in the filename
 * @path:     The path of the file
 *
 * This contains all information we need about a file.
 */
struct file {
        struct stat st;
        struct file *next;
        struct link {
                struct link *next;
                int basename;
#if __STDC_VERSION__ >= 199901L
                char path[];
#elif __GNUC__
                char path[0];
#else
                char path[1];
#endif
        } *links;
};

/**
 * enum log_level - Logging levels
 * @JLOG_SUMMARY: Default log level
 * @JLOG_INFO:    Verbose logging (verbose == 1)
 * @JLOG_VERBOSE1:  Verbosity 2
 * @JLOG_VERBOSE2:  Verbosity 3
 */
enum log_level {
        JLOG_SUMMARY,
        JLOG_INFO,
        JLOG_VERBOSE1,
        JLOG_VERBOSE2
};

/**
 * struct statistic - Statistics about the file
 * @started: Whether we are post command-line processing
 * @files: The number of files worked on
 * @linked: The number of files replaced by a hardlink to a master
 * @xattr_comparisons: The number of extended attribute comparisons
 * @comparisons: The number of comparisons
 * @saved: The (exaggerated) amount of space saved
 * @start_time: The time we started at
 */
static struct statistics {
        int started;
        size_t files;
        size_t linked;
        size_t xattr_comparisons;
        size_t comparisons;
        double saved;
        struct timeval start_time;
} stats;

/**
 * struct options - Processed command-line options
 * @include: A linked list of regular expressions for the --include option
 * @exclude: A linked list of regular expressions for the --exclude option
 * @verbosity: The verbosity. Should be one of #enum log_level
 * @respect_mode: Whether to respect file modes (default = TRUE)
 * @respect_owner: Whether to respect file owners (uid, gid; default = TRUE)
 * @respect_name: Whether to respect file names (default = FALSE)
 * @respect_time: Whether to respect file modification times (default = TRUE)
 * @respect_xattrs: Whether to respect extended attributes (default = FALSE)
 * @maximise: Chose the file with the highest link count as master
 * @minimise: Chose the file with the lowest link count as master
 * @keep_oldest: Choose the file with oldest timestamp as master (default = FALSE)
 * @dry_run: Specifies whether hardlink should not link files (default = FALSE)
 * @min_size: Minimum size of files to consider. (default = 1 byte)
 */
static struct options {
        struct regex_link {
                regex_t preg;
                struct regex_link *next;
        } *include, *exclude;

        signed int verbosity;
        unsigned int respect_mode:1;
        unsigned int respect_owner:1;
        unsigned int respect_name:1;
        unsigned int respect_time:1;
        unsigned int respect_xattrs:1;
        unsigned int maximise:1;
        unsigned int minimise:1;
        unsigned int keep_oldest:1;
        unsigned int dry_run:1;
        uintmax_t min_size;
} opts = {
        /* default setting */
        .respect_mode = TRUE,
        .respect_owner = TRUE,
        .respect_time = TRUE,
        .respect_xattrs = FALSE,
        .keep_oldest = FALSE,
        .min_size = 1
};

/*
 * files
 *
 * A binary tree of files, managed using tsearch(). To see which nodes
 * are considered equal, see compare_nodes()
 */
static void *files;
static void *files_by_ino;

/*
 * last_signal
 *
 * The last signal we received. We store the signal here in order to be able
 * to break out of loops gracefully and to return from our nftw() handler.
 */
static int last_signal;

/**
 * jlog - Logging for hardlink
 * @level: The log level
 * @format: A format string for printf()
 */
__attribute__((format(printf, 2, 3)))
static void jlog(enum log_level level, const char *format, ...)
{
        va_list args;

        if (quiet || level > (unsigned int)opts.verbosity)
                return;

        va_start(args, format);
        vfprintf(stdout, format, args);
        va_end(args);
        fputc('\n', stdout);
}

/**
 * CMP - Compare two numerical values, return 1, 0, or -1
 * @a: First value
 * @b: Second value
 *
 * Used to compare two integers of any size while avoiding overflow.
 */
#define CMP(a, b) ((a) > (b) ? 1 : ((a) < (b) ? -1 : 0))

/**
 * regexec_any - Match against multiple regular expressions
 * @pregs: A linked list of regular expressions
 * @what:  The string to match against
 *
 * Checks whether any of the regular expressions in the list matches the
 * string.
 */
static int regexec_any(struct regex_link *pregs, const char *what)
{
        for (; pregs != NULL; pregs = pregs->next) {
                if (regexec(&pregs->preg, what, 0, NULL, 0) == 0)
                        return TRUE;
        }
        return FALSE;
}

/**
 * compare_nodes - Node comparison function
 * @_a: The first node (a #struct file)
 * @_b: The second node (a #struct file)
 *
 * Compare the two nodes for the binary tree.
 */
static int compare_nodes(const void *_a, const void *_b)
{
        const struct file *a = _a;
        const struct file *b = _b;
        int diff = 0;

        if (diff == 0)
                diff = CMP(a->st.st_dev, b->st.st_dev);
        if (diff == 0)
                diff = CMP(a->st.st_size, b->st.st_size);

        return diff;
}

/**
 * compare_nodes_ino - Node comparison function
 * @_a: The first node (a #struct file)
 * @_b: The second node (a #struct file)
 *
 * Compare the two nodes for the binary tree.
 */
static int compare_nodes_ino(const void *_a, const void *_b)
{
        const struct file *a = _a;
        const struct file *b = _b;
        int diff = 0;

        if (diff == 0)
                diff = CMP(a->st.st_dev, b->st.st_dev);
        if (diff == 0)
                diff = CMP(a->st.st_ino, b->st.st_ino);

        /* If opts.respect_name is used, we will restrict a struct file to
         * contain only links with the same basename to keep the rest simple.
         */
        if (diff == 0 && opts.respect_name)
                diff = strcmp(a->links->path + a->links->basename,
                              b->links->path + b->links->basename);

        return diff;
}

/**
 * print_stats - Print statistics to stdout
 */
static void print_stats(void)
{
        struct timeval end = { 0, 0 }, delta = { 0, 0 };
        char *ssz;

        gettime_monotonic(&end);
        timersub(&end, &stats.start_time, &delta);

        jlog(JLOG_SUMMARY, "%-15s %s", _("Mode:"),
             opts.dry_run ? _("dry-run") : _("real"));
        jlog(JLOG_SUMMARY, "%-15s %zu", _("Files:"), stats.files);
        jlog(JLOG_SUMMARY, _("%-15s %zu files"), _("Linked:"), stats.linked);

#ifdef HAVE_SYS_XATTR_H
        jlog(JLOG_SUMMARY, _("%-15s %zu xattrs"), _("Compared:"),
             stats.xattr_comparisons);
#endif
        jlog(JLOG_SUMMARY, _("%-15s %zu files"), _("Compared:"),
             stats.comparisons);

        ssz = size_to_human_string(SIZE_SUFFIX_3LETTER |
                                   SIZE_SUFFIX_SPACE |
                                   SIZE_DECIMAL_2DIGITS, stats.saved);

        jlog(JLOG_SUMMARY, "%-15s %s", _("Saved:"), ssz);
        free(ssz);

        jlog(JLOG_SUMMARY, _("%-15s %ld.%06ld seconds"), _("Duration:"),
             (long)delta.tv_sec, (long)delta.tv_usec);
}

/**
 * handle_interrupt - Handle a signal
 *
 * Returns: %TRUE on SIGINT, SIGTERM; %FALSE on all other signals.
 */
static int handle_interrupt(void)
{
        switch (last_signal) {
        case SIGINT:
        case SIGTERM:
                return TRUE;
        case SIGUSR1:
                print_stats();
                putchar('\n');
                break;
        }

        last_signal = 0;
        return FALSE;
}

#ifdef HAVE_SYS_XATTR_H

/**
 * llistxattr_or_die - Wrapper for llistxattr()
 *
 * This does the same thing as llistxattr() except that it aborts if any error
 * other than "not supported" is detected.
 */
static ssize_t llistxattr_or_die(const char *path, char *list, size_t size)
{
        ssize_t len = llistxattr(path, list, size);

        if (len < 0 && errno != ENOTSUP)
                err(EXIT_FAILURE, _("cannot get xattr names for %s"), path);

        return len;
}

/**
 * lgetxattr_or_die - Wrapper for lgetxattr()
 *
 * This does the same thing as lgetxattr() except that it aborts upon error.
 */
static ssize_t lgetxattr_or_die(const char *path,
                        const char *name, void *value, size_t size)
{
        ssize_t len = lgetxattr(path, name, value, size);

        if (len < 0)
                err(EXIT_FAILURE, _("cannot get xattr value of %s for %s"),
                    name, path);

        return len;
}

/**
 * get_xattr_name_count - Count the number of xattr names
 * @names: a non-empty table of concatenated, null-terminated xattr names
 * @len: the total length of the table
 *
 * @Returns the number of xattr names
 */
static int get_xattr_name_count(const char *const names, ssize_t len)
{
        int count = 0;
        const char *name;

        for (name = names; name < (names + len); name += strlen(name) + 1)
                count++;

        return count;
}

/**
 * cmp_xattr_name_ptrs - Compare two pointers to xattr names by comparing
 * the names they point to.
 */
static int cmp_xattr_name_ptrs(const void *ptr1, const void *ptr2)
{
        return strcmp(*(char *const *)ptr1, *(char *const *)ptr2);
}

/**
 * get_sorted_xattr_name_table - Create a sorted table of xattr names.
 * @names - table of concatenated, null-terminated xattr names
 * @n - the number of names
 *
 * @Returns allocated table of pointers to the names, sorted alphabetically
 */
static const char **get_sorted_xattr_name_table(const char *names, int n)
{
        const char **table = xmalloc(n * sizeof(char *));
        int i;

        for (i = 0; i < n; i++) {
                table[i] = names;
                names += strlen(names) + 1;
        }

        qsort(table, n, sizeof(char *), cmp_xattr_name_ptrs);

        return table;
}

/**
 * file_xattrs_equal - Compare the extended attributes of two files
 * @a: The first file
 * @b: The second file
 *
 * @Returns: %TRUE if and only if extended attributes are equal
 */
static int file_xattrs_equal(const struct file *a, const struct file *b)
{
        ssize_t len_a;
        ssize_t len_b;
        char *names_a = NULL;
        char *names_b = NULL;
        int n_a;
        int n_b;
        const char **name_ptrs_a = NULL;
        const char **name_ptrs_b = NULL;
        void *value_a = NULL;
        void *value_b = NULL;
        int ret = FALSE;
        int i;

        assert(a->links != NULL);
        assert(b->links != NULL);

        jlog(JLOG_VERBOSE1, _("Comparing xattrs of %s to %s"), a->links->path,
             b->links->path);

        stats.xattr_comparisons++;

        len_a = llistxattr_or_die(a->links->path, NULL, 0);
        len_b = llistxattr_or_die(b->links->path, NULL, 0);

        if (len_a <= 0 && len_b <= 0)
                return TRUE;    // xattrs not supported or neither file has any

        if (len_a != len_b)
                return FALSE;   // total lengths of xattr names differ

        names_a = xmalloc(len_a);
        names_b = xmalloc(len_b);

        len_a = llistxattr_or_die(a->links->path, names_a, len_a);
        len_b = llistxattr_or_die(b->links->path, names_b, len_b);
        assert((len_a > 0) && (len_a == len_b));

        n_a = get_xattr_name_count(names_a, len_a);
        n_b = get_xattr_name_count(names_b, len_b);

        if (n_a != n_b)
                goto exit;      // numbers of xattrs differ

        name_ptrs_a = get_sorted_xattr_name_table(names_a, n_a);
        name_ptrs_b = get_sorted_xattr_name_table(names_b, n_b);

        // We now have two sorted tables of xattr names.

        for (i = 0; i < n_a; i++) {
                if (handle_interrupt())
                        goto exit;      // user wants to quit

                if (strcmp(name_ptrs_a[i], name_ptrs_b[i]) != 0)
                        goto exit;      // names at same slot differ

                len_a =
                    lgetxattr_or_die(a->links->path, name_ptrs_a[i], NULL, 0);
                len_b =
                    lgetxattr_or_die(b->links->path, name_ptrs_b[i], NULL, 0);

                if (len_a != len_b)
                        goto exit;      // xattrs with same name, different value lengths

                value_a = xmalloc(len_a);
                value_b = xmalloc(len_b);

                len_a = lgetxattr_or_die(a->links->path, name_ptrs_a[i],
                                         value_a, len_a);
                len_b = lgetxattr_or_die(b->links->path, name_ptrs_b[i],
                                         value_b, len_b);
                assert((len_a >= 0) && (len_a == len_b));

                if (memcmp(value_a, value_b, len_a) != 0)
                        goto exit;      // xattrs with same name, different values

                free(value_a);
                free(value_b);
                value_a = NULL;
                value_b = NULL;
        }

        ret = TRUE;

 exit:
        free(names_a);
        free(names_b);
        free(name_ptrs_a);
        free(name_ptrs_b);
        free(value_a);
        free(value_b);
        return ret;
}
#else /* !HAVE_SYS_XATTR_H */
static int file_xattrs_equal(const struct file *a, const struct file *b)
{
        return TRUE;
}
#endif /* HAVE_SYS_XATTR_H */

/**
 * file_contents_equal - Compare contents of two files for equality
 * @a: The first file
 * @b: The second file
 *
 * Compare the contents of the files for equality
 */
static int file_contents_equal(const struct file *a, const struct file *b)
{
        FILE *fa = NULL;
        FILE *fb = NULL;
        char buf_a[8192];
        char buf_b[8192];
        int cmp = 0;            /* zero => equal */
        off_t off = 0;          /* current offset */

        assert(a->links != NULL);
        assert(b->links != NULL);

        jlog(JLOG_VERBOSE1, _("Comparing %s to %s"), a->links->path,
             b->links->path);

        stats.comparisons++;

        if ((fa = fopen(a->links->path, "rb")) == NULL)
                goto err;
        if ((fb = fopen(b->links->path, "rb")) == NULL)
                goto err;

#if defined(POSIX_FADV_SEQUENTIAL) && defined(HAVE_POSIX_FADVISE)
        posix_fadvise(fileno(fa), 0, 0, POSIX_FADV_SEQUENTIAL);
        posix_fadvise(fileno(fb), 0, 0, POSIX_FADV_SEQUENTIAL);
#endif

        while (!handle_interrupt() && cmp == 0) {
                size_t ca;
                size_t cb;

                ca = fread(buf_a, 1, sizeof(buf_a), fa);
                if (ca < sizeof(buf_a) && ferror(fa))
                        goto err;

                cb = fread(buf_b, 1, sizeof(buf_b), fb);
                if (cb < sizeof(buf_b) && ferror(fb))
                        goto err;

                off += ca;

                if ((ca != cb || ca == 0)) {
                        cmp = CMP(ca, cb);
                        break;
                }
                cmp = memcmp(buf_a, buf_b, ca);
        }
 out:
        if (fa != NULL)
                fclose(fa);
        if (fb != NULL)
                fclose(fb);
        return !handle_interrupt() && cmp == 0;
 err:
        if (fa == NULL || fb == NULL)
                warn(_("cannot open %s"), fa ? b->links->path : a->links->path);
        else
                warn(_("cannot read %s"),
                     ferror(fa) ? a->links->path : b->links->path);
        cmp = 1;
        goto out;
}

/**
 * file_may_link_to - Check whether a file may replace another one
 * @a: The first file
 * @b: The second file
 *
 * Check whether the two fies are considered equal and can be linked
 * together. If the two files are identical, the result will be FALSE,
 * as replacing a link with an identical one is stupid.
 */
static int file_may_link_to(const struct file *a, const struct file *b)
{
        return (a->st.st_size != 0 &&
                a->st.st_size == b->st.st_size &&
                a->links != NULL && b->links != NULL &&
                a->st.st_dev == b->st.st_dev &&
                a->st.st_ino != b->st.st_ino &&
                (!opts.respect_mode || a->st.st_mode == b->st.st_mode) &&
                (!opts.respect_owner || a->st.st_uid == b->st.st_uid) &&
                (!opts.respect_owner || a->st.st_gid == b->st.st_gid) &&
                (!opts.respect_time || a->st.st_mtime == b->st.st_mtime) &&
                (!opts.respect_name
                 || strcmp(a->links->path + a->links->basename,
                           b->links->path + b->links->basename) == 0) &&
                (!opts.respect_xattrs || file_xattrs_equal(a, b)) &&
                file_contents_equal(a, b));
}

/**
 * file_compare - Compare two files to decide which should be master
 * @a: The first file
 * @b: The second file
 *
 * Check which of the files should be considered greater and thus serve
 * as the master when linking (the master is the file that all equal files
 * will be replaced with).
 */
static int file_compare(const struct file *a, const struct file *b)
{
        int res = 0;
        if (a->st.st_dev == b->st.st_dev && a->st.st_ino == b->st.st_ino)
                return 0;

        if (res == 0 && opts.maximise)
                res = CMP(a->st.st_nlink, b->st.st_nlink);
        if (res == 0 && opts.minimise)
                res = CMP(b->st.st_nlink, a->st.st_nlink);
        if (res == 0)
                res = opts.keep_oldest ? CMP(b->st.st_mtime, a->st.st_mtime)
                    : CMP(a->st.st_mtime, b->st.st_mtime);
        if (res == 0)
                res = CMP(b->st.st_ino, a->st.st_ino);

        return res;
}

/**
 * file_link - Replace b with a link to a
 * @a: The first file
 * @b: The second file
 *
 * Link the file, replacing @b with the current one. The file is first
 * linked to a temporary name, and then renamed to the name of @b, making
 * the replace atomic (@b will always exist).
 */
static int file_link(struct file *a, struct file *b)
{
        char *ssz;

 file_link:
        assert(a->links != NULL);
        assert(b->links != NULL);

        ssz = size_to_human_string(SIZE_SUFFIX_3LETTER |
                                   SIZE_SUFFIX_SPACE |
                                   SIZE_DECIMAL_2DIGITS, a->st.st_size);
        jlog(JLOG_INFO, _("%sLinking %s to %s (-%s)"),
             opts.dry_run ? _("[DryRun] ") : "", a->links->path, b->links->path,
             ssz);
        free(ssz);

        if (!opts.dry_run) {
                size_t len =
                    strlen(b->links->path) + strlen(".hardlink-temporary") + 1;
                char *new_path = xmalloc(len);

                snprintf(new_path, len, "%s.hardlink-temporary",
                         b->links->path);

                if (link(a->links->path, new_path) != 0) {
                        warn(_("cannot link %s to %s"), a->links->path,
                             new_path);
                        free(new_path);
                        return FALSE;
                } else if (rename(new_path, b->links->path) != 0) {
                        warn(_("cannot rename %s to %s"), a->links->path,
                             new_path);
                        unlink(new_path);       /* cleanup failed rename */
                        free(new_path);
                        return FALSE;
                }
                free(new_path);
        }

        /* Update statistics */
        stats.linked++;

        /* Increase the link count of this file, and set stat() of other file */
        a->st.st_nlink++;
        b->st.st_nlink--;

        if (b->st.st_nlink == 0)
                stats.saved += a->st.st_size;

        /* Move the link from file b to a */
        {
                struct link *new_link = b->links;

                b->links = b->links->next;
                new_link->next = a->links->next;
                a->links->next = new_link;
        }

        /* Do it again */
        if (b->links)
                goto file_link;

        return TRUE;
}

/**
 * inserter - Callback function for nftw()
 * @fpath: The path of the file being visited
 * @sb:    The stat information of the file
 * @typeflag: The type flag
 * @ftwbuf:   Contains current level of nesting and offset of basename
 *
 * Called by nftw() for the files. See the manual page for nftw() for
 * further information.
 */
static int inserter(const char *fpath, const struct stat *sb,
                    int typeflag, struct FTW *ftwbuf)
{
        struct file *fil;
        struct file **node;
        size_t pathlen;
        int included;
        int excluded;

        if (handle_interrupt())
                return 1;
        if (typeflag == FTW_DNR || typeflag == FTW_NS)
                warn(_("cannot read %s"), fpath);
        if (typeflag != FTW_F || !S_ISREG(sb->st_mode))
                return 0;

        included = regexec_any(opts.include, fpath);
        excluded = regexec_any(opts.exclude, fpath);

        if ((opts.exclude && excluded && !included) ||
            (!opts.exclude && opts.include && !included))
                return 0;

        stats.files++;

        if ((uintmax_t) sb->st_size < opts.min_size) {
                jlog(JLOG_VERBOSE1,
                     _("Skipped %s (smaller than configured size)"), fpath);
                return 0;
        }

        jlog(JLOG_VERBOSE2, _("Visiting %s (file %zu)"), fpath, stats.files);

        pathlen = strlen(fpath) + 1;

        fil = xcalloc(1, sizeof(*fil));
        fil->links = xcalloc(1, sizeof(struct link) + pathlen);

        fil->st = *sb;
        fil->links->basename = ftwbuf->base;
        fil->links->next = NULL;

        memcpy(fil->links->path, fpath, pathlen);

        node = tsearch(fil, &files_by_ino, compare_nodes_ino);

        if (node == NULL)
                goto fail;

        if (*node != fil) {
                /* Already known inode, add link to inode information */
                assert((*node)->st.st_dev == sb->st_dev);
                assert((*node)->st.st_ino == sb->st_ino);

                fil->links->next = (*node)->links;
                (*node)->links = fil->links;

                free(fil);
        } else {
                /* New inode, insert into by-size table */
                node = tsearch(fil, &files, compare_nodes);

                if (node == NULL)
                        goto fail;

                if (*node != fil) {
                        struct file *l;

                        if (file_compare(fil, *node) >= 0) {
                                fil->next = *node;
                                *node = fil;
                        } else {
                                for (l = *node; l != NULL; l = l->next) {
                                        if (l->next != NULL
                                            && file_compare(fil, l->next) < 0)
                                                continue;

                                        fil->next = l->next;
                                        l->next = fil;

                                        break;
                                }
                        }
                }
        }

        return 0;

 fail:
        warn(_("cannot continue"));     /* probably ENOMEM */
        return 0;
}

/**
 * visitor - Callback for twalk()
 * @nodep: Pointer to a pointer to a #struct file
 * @which: At which point this visit is (preorder, postorder, endorder)
 * @depth: The depth of the node in the tree
 *
 * Visit the nodes in the binary tree. For each node, call hardlinker()
 * on each #struct file in the linked list of #struct file instances located
 * at that node.
 */
static void visitor(const void *nodep, const VISIT which, const int depth)
{
        struct file *master = *(struct file **)nodep;
        struct file *other;

        (void)depth;

        if (which != leaf && which != endorder)
                return;

        for (; master != NULL; master = master->next) {
                if (handle_interrupt())
                        exit(EXIT_FAILURE);
                if (master->links == NULL)
                        continue;

                for (other = master->next; other != NULL; other = other->next) {
                        if (handle_interrupt())
                                exit(EXIT_FAILURE);

                        assert(other != other->next);
                        assert(other->st.st_size == master->st.st_size);

                        if (other->links == NULL
                            || !file_may_link_to(master, other))
                                continue;

                        if (!file_link(master, other) && errno == EMLINK)
                                master = other;
                }
        }
}

/**
 * usage - Print the program help and exit
 */
static void __attribute__((__noreturn__)) usage(void)
{
        FILE *out = stdout;

        fputs(USAGE_HEADER, out);
        fprintf(out, _(" %s [options] <directory>|<file> ...\n"),
                program_invocation_short_name);

        fputs(USAGE_SEPARATOR, out);
        fputs(_("Consolidate duplicate files using hardlinks.\n"), out);

        fputs(USAGE_OPTIONS, out);
        fputs(_(" -v, --verbose              verbose output (repeat for more verbosity)\n"), out);
        fputs(_(" -q, --quiet                quiet mode - don't print anything\n"), out);
        fputs(_(" -n, --dry-run              don't actually link anything\n"), out);
        fputs(_(" -f, --respect-name         filenames have to be identical\n"), out);
        fputs(_(" -p, --ignore-mode          ignore changes of file mode\n"), out);
        fputs(_(" -o, --ignore-owner         ignore owner changes\n"), out);
        fputs(_(" -t, --ignore-time          ignore timestamps (when testing for equality)\n"), out);
#ifdef HAVE_SYS_XATTR_H
        fputs(_(" -X, --respect-xattrs       respect extended attributes\n"), out);
#endif
        fputs(_(" -m, --maximize             maximize the hardlink count, remove the file with\n"
                "                              lowest hardlink count\n"), out);
        fputs(_(" -M, --minimize             reverse the meaning of -m\n"), out);
        fputs(_(" -O, --keep-oldest          keep the oldest file of multiple equal files\n"
                "                              (lower precedence than minimize/maximize)\n"), out);
        fputs(_(" -x, --exclude <regex>      regular expression to exclude files\n"), out);
        fputs(_(" -i, --include <regex>      regular expression to include files/dirs\n"), out);
        fputs(_(" -s, --minimum-size <size>  minimum size for files.\n"), out);
        fputs(_(" -c, --content              compare only file contents, same as -pot\n"), out);

        fputs(USAGE_SEPARATOR, out);
        printf(USAGE_HELP_OPTIONS(28));
        printf(USAGE_MAN_TAIL("hardlink(1)"));

        exit(EXIT_SUCCESS);
}

/**
 * register_regex - Compile and insert a regular expression into list
 * @pregs: Pointer to a linked list of regular expressions
 * @regex: String containing the regular expression to be compiled
 */
static void register_regex(struct regex_link **pregs, const char *regex)
{
        struct regex_link *link;
        int err;

        link = xmalloc(sizeof(*link));

        if ((err = regcomp(&link->preg, regex, REG_NOSUB | REG_EXTENDED)) != 0) {
                size_t size = regerror(err, &link->preg, NULL, 0);
                char *buf = xmalloc(size + 1);

                regerror(err, &link->preg, buf, size);

                errx(EXIT_FAILURE, _("could not compile regular expression %s: %s"),
                                regex, buf);
        }
        link->next = *pregs; *pregs = link;
}

/**
 * parse_options - Parse the command line options
 * @argc: Number of options
 * @argv: Array of options
 */
static int parse_options(int argc, char *argv[])
{
        static const char optstr[] = "VhvnfpotXcmMOx:i:s:q";
        static const struct option long_options[] = {
                {"version", no_argument, NULL, 'V'},
                {"help", no_argument, NULL, 'h'},
                {"verbose", no_argument, NULL, 'v'},
                {"dry-run", no_argument, NULL, 'n'},
                {"respect-name", no_argument, NULL, 'f'},
                {"ignore-mode", no_argument, NULL, 'p'},
                {"ignore-owner", no_argument, NULL, 'o'},
                {"ignore-time", no_argument, NULL, 't'},
                {"respect-xattrs", no_argument, NULL, 'X'},
                {"maximize", no_argument, NULL, 'm'},
                {"minimize", no_argument, NULL, 'M'},
                {"keep-oldest", no_argument, NULL, 'O'},
                {"exclude", required_argument, NULL, 'x'},
                {"include", required_argument, NULL, 'i'},
                {"minimum-size", required_argument, NULL, 's'},
                {"content", no_argument, NULL, 'c'},
                {"quiet", no_argument, NULL, 'q'},
                {NULL, 0, NULL, 0}
        };
        static const ul_excl_t excl[] = {
                {'q', 'v'},
                {0}
        };
        int excl_st[ARRAY_SIZE(excl)] = UL_EXCL_STATUS_INIT;
        int c;

        while ((c = getopt_long(argc, argv, optstr, long_options, NULL)) != -1) {

                err_exclusive_options(c, long_options, excl, excl_st);

                switch (c) {
                case 'p':
                        opts.respect_mode = FALSE;
                        break;
                case 'o':
                        opts.respect_owner = FALSE;
                        break;
                case 't':
                        opts.respect_time = FALSE;
                        break;
                case 'X':
                        opts.respect_xattrs = TRUE;
                        break;
                case 'm':
                        opts.maximise = TRUE;
                        break;
                case 'M':
                        opts.minimise = TRUE;
                        break;
                case 'O':
                        opts.keep_oldest = TRUE;
                        break;
                case 'f':
                        opts.respect_name = TRUE;
                        break;
                case 'v':
                        opts.verbosity++;
                        break;
                case 'q':
                        quiet = TRUE;
                        break;
                case 'c':
                        opts.respect_mode = FALSE;
                        opts.respect_name = FALSE;
                        opts.respect_owner = FALSE;
                        opts.respect_time = FALSE;
                        opts.respect_xattrs = FALSE;
                        break;
                case 'n':
                        opts.dry_run = 1;
                        break;
                case 'x':
                        register_regex(&opts.exclude, optarg);
                        break;
                case 'i':
                        register_regex(&opts.include, optarg);
                        break;
                case 's':
                        opts.min_size = strtosize_or_err(optarg, _("failed to parse size"));
                        break;
                case 'h':
                        usage();
                case 'V':
                        print_version(EXIT_SUCCESS);
                default:
                        errtryhelp(EXIT_FAILURE);}
        }

        return 0;
}

/**
* to_be_called_atexit - Cleanup handler, also prints statistics.
*/
static void to_be_called_atexit(void)
{
        if (stats.started)
                print_stats();
}

/**
* sighandler - Signal handler, sets the global last_signal variable
* @i: The signal number
*/
static void sighandler(int i)
{
        if (last_signal != SIGINT)
                last_signal = i;
        if (i == SIGINT)
                putchar('\n');
}

int main(int argc, char *argv[])
{
        struct sigaction sa;

        sa.sa_handler = sighandler;
        sa.sa_flags = SA_RESTART;
        sigfillset(&sa.sa_mask);

        /* If we receive a SIGINT, end the processing */
        sigaction(SIGINT, &sa, NULL);
        sigaction(SIGUSR1, &sa, NULL);

        /* Pretty print numeric output */
        setlocale(LC_NUMERIC, "");

        if (atexit(to_be_called_atexit) != 0)
                err(EXIT_FAILURE, _("cannot register exit handler"));

        parse_options(argc, argv);

        if (optind == argc)
                errx(EXIT_FAILURE, _("no directory or dile specified"));

        gettime_monotonic(&stats.start_time);
        stats.started = TRUE;

        for (; optind < argc; optind++) {
                if (nftw(argv[optind], inserter, 20, FTW_PHYS) == -1)
                        warn(_("cannot process %s"), argv[optind]);
        }

        twalk(files, visitor);
        return 0;
}