chsh: make readline completion to propose valid shells

This is better than default readline completion, that gives paths from
current directory onwards.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>

diff --git a/login-utils/chsh.c b/login-utils/chsh.c
index 1fb377593cf37e7a2b1de1b104afb7ffd25c2589..c6eab15541ed02b2b5c50b3b909a669ccaf68aea 100644 (file)
--- a/login-utils/chsh.c
+++ b/login-utils/chsh.c
@@ -67,6 +67,8 @@ struct sinfo {
        char *shell;
 };
 
+/* global due readline completion */
+static char **global_shells = NULL;
 
 static void __attribute__((__noreturn__)) usage (FILE *fp)
 {
@@ -87,24 +89,31 @@ static void __attribute__((__noreturn__)) usage (FILE *fp)
 }
 
 /*
- *  get_shell_list () -- if the given shell appears in /etc/shells,
- *     return true.  if not, return false.
- *     if the given shell is NULL, /etc/shells is outputted to stdout.
+ *  free_shells () -- free shells allocations.
  */
-static int get_shell_list(const char *shell_name)
+static void free_shells(void)
+{
+       char **s;
+
+       for (s = global_shells; *s; s++)
+               free(*s);
+       free(global_shells);
+}
+
+/*
+ *  init_shells () -- fill shells variable from /etc/shells,
+ */
+static int init_shells(char ***shells)
 {
        FILE *fp;
-       int found = 0;
        char *buf = NULL;
-       size_t sz = 0;
+       size_t sz = 0, shellsz = 8, n = 0;
        ssize_t len;
 
+       *shells = xmalloc(sizeof(char *) * shellsz);
        fp = fopen(_PATH_SHELLS, "r");
-       if (!fp) {
-               if (!shell_name)
-                       warnx(_("No known shells."));
-               return 0;
-       }
+       if (!fp)
+               return 1;
        while ((len = getline(&buf, &sz, fp)) != -1) {
                /* ignore comments and blank lines */
                if (*buf == '#' || len < 2)
@@ -112,26 +121,77 @@ static int get_shell_list(const char *shell_name)
                /* strip the ending newline */
                if (buf[len - 1] == '\n')
                        buf[len - 1] = 0;
-               /* check or output the shell */
+               (*shells)[n++] = buf;
+               if (shellsz < n) {
+                       shellsz *= 2;
+                       shells = xrealloc(shells, sizeof(char *) * shellsz);
+               }
+               buf = NULL;
+       }
+       free(buf);
+       (*shells)[n] = NULL;
+       fclose(fp);
+       atexit(free_shells);
+       return 0;
+}
+
+/*
+ *  get_shell_list () -- if the given shell appears in /etc/shells,
+ *     return true.  if not, return false.
+ *     if the given shell is NULL, /etc/shells is outputted to stdout.
+ */
+static int get_shell_list(const char *shell_name, char ***shells)
+{
+       char **s;
+       int found = 0;
+
+       if (!shells)
+               return found;
+       s = *shells;
+       for (s = *shells; *s; s++) {
                if (shell_name) {
-                       if (!strcmp(shell_name, buf)) {
+                       if (!strcmp(shell_name, *s)) {
                                found = 1;
                                break;
                        }
                } else
-                       printf("%s\n", buf);
+                       printf("%s\n", *s);
        }
-       fclose(fp);
-       free(buf);
        return found;
 }
 
+#ifdef HAVE_LIBREADLINE
+static char *shell_name_generator(const char *text, int state)
+{
+       static size_t len, idx;
+       char *s;
+
+       if (!state) {
+               idx = 0;
+               len = strlen(text);
+       }
+       while ((s = global_shells[idx++])) {
+               if (strncmp(s, text, len) == 0)
+                       return xstrdup(s);
+       }
+       return NULL;
+}
+
+static char **shell_name_completion(const char *text,
+                                   int start __attribute__((__unused__)),
+                                   int end __attribute__((__unused__)))
+{
+       rl_attempted_completion_over = 1;
+       return rl_completion_matches(text, shell_name_generator);
+}
+#endif
+
 /*
  *  parse_argv () --
  *     parse the command line arguments, and fill in "pinfo" with any
  *     information from the command line.
  */
-static void parse_argv(int argc, char **argv, struct sinfo *pinfo)
+static void parse_argv(int argc, char **argv, struct sinfo *pinfo, char ***shells)
 {
        static const struct option long_options[] = {
                {"shell",       required_argument, NULL, 's'},
@@ -151,7 +211,8 @@ static void parse_argv(int argc, char **argv, struct sinfo *pinfo)
                case 'h':
                        usage(stdout);
                case 'l':
-                       get_shell_list(NULL);
+                       init_shells(shells);
+                       get_shell_list(NULL, shells);
                        exit(EXIT_SUCCESS);
                case 's':
                        if (!optarg)
@@ -178,15 +239,16 @@ static char *ask_new_shell(char *question, char *oldshell)
 {
        int len;
        char *ans = NULL;
-#ifndef HAVE_LIBREADLINE
+#ifdef HAVE_LIBREADLINE
+       rl_attempted_completion_function = shell_name_completion;
+#else
        size_t dummy = 0;
 #endif
-
        if (!oldshell)
                oldshell = "";
-       printf("%s [%s]: ", question, oldshell);
+       printf("%s [%s]\n", question, oldshell);
 #ifdef HAVE_LIBREADLINE
-       if ((ans = readline(NULL)) == NULL)
+       if ((ans = readline("> ")) == NULL)
 #else
        if (getline(&ans, &dummy, stdin) < 0)
 #endif
@@ -203,7 +265,7 @@ static char *ask_new_shell(char *question, char *oldshell)
  *  check_shell () -- if the shell is completely invalid, print
  *     an error and exit.
  */
-static void check_shell(const char *shell)
+static void check_shell(const char *shell, char ***shells)
 {
        if (*shell != '/')
                errx(EXIT_FAILURE, _("shell must be a full path name"));
@@ -213,7 +275,7 @@ static void check_shell(const char *shell)
                errx(EXIT_FAILURE, _("\"%s\" is not executable"), shell);
        if (illegal_passwd_chars(shell))
                errx(EXIT_FAILURE, _("%s: has illegal characters"), shell);
-       if (!get_shell_list(shell)) {
+       if (!get_shell_list(shell, shells)) {
 #ifdef ONLY_LISTED_SHELLS
                if (!getuid())
                        warnx(_("Warning: \"%s\" is not listed in %s."), shell,
@@ -245,7 +307,7 @@ int main(int argc, char **argv)
        textdomain(PACKAGE);
        atexit(close_stdout);
 
-       parse_argv(argc, argv, &info);
+       parse_argv(argc, argv, &info, &global_shells);
        if (!info.username) {
                pw = getpwuid(uid);
                if (!pw)
@@ -304,7 +366,8 @@ int main(int argc, char **argv)
                    _("running UID doesn't match UID of user we're "
                      "altering, shell change denied"));
        }
-       if (uid != 0 && !get_shell_list(oldshell)) {
+       init_shells(&global_shells);
+       if (uid != 0 && !get_shell_list(oldshell, &global_shells)) {
                errno = EACCES;
                err(EXIT_FAILURE, _("your shell is not in %s, "
                                    "shell change denied"), _PATH_SHELLS);
@@ -323,7 +386,7 @@ int main(int argc, char **argv)
                        return EXIT_SUCCESS;
        }
 
-       check_shell(info.shell);
+       check_shell(info.shell, &global_shells);
 
        if (!nullshell && strcmp(oldshell, info.shell) == 0)
                errx(EXIT_SUCCESS, _("Shell not changed."));