1 /* getusershell.c -- Return names of valid user shells.
3 Copyright (C) 1991, 1997, 2000-2001, 2003-2006, 2008-2012 Free Software
6 This program is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3 of the License, or
9 (at your option) any later version.
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>. */
19 /* Written by David MacKenzie <djm@gnu.ai.mit.edu> */
28 /* File containing a list of nonrestricted shells, one per line. */
29 # define SHELLS_FILE "/etc/shells"
31 /* This is a horrible kludge. Isn't there a better way? */
32 # define SHELLS_FILE "/dev/env/DJDIR/etc/shells"
43 # include "unlocked-io.h"
46 static size_t readname (char **, size_t *, FILE *);
48 #if ! defined ADDITIONAL_DEFAULT_SHELLS && defined __MSDOS__
49 # define ADDITIONAL_DEFAULT_SHELLS \
50 "c:/dos/command.com", "c:/windows/command.com", "c:/command.com",
52 # define ADDITIONAL_DEFAULT_SHELLS /* empty */
55 /* List of shells to use if the shells file is missing. */
56 static char const* const default_shells[] =
58 ADDITIONAL_DEFAULT_SHELLS
59 "/bin/sh", "/bin/csh", "/usr/bin/sh", "/usr/bin/csh", NULL
62 /* Index of the next shell in 'default_shells' to return.
63 0 means we are not using 'default_shells'. */
64 static size_t default_index = 0;
66 /* Input stream from the shells file. */
67 static FILE *shellstream = NULL;
69 /* Line of input from the shells file. */
70 static char *line = NULL;
72 /* Number of bytes allocated for 'line'. */
73 static size_t line_size = 0;
75 /* Return an entry from the shells file, ignoring comment lines.
76 If the file doesn't exist, use the list in DEFAULT_SHELLS (above).
77 In any case, the returned string is in memory allocated through malloc.
78 Return NULL if there are no more entries. */
83 if (default_index > 0)
85 if (default_shells[default_index])
86 /* Not at the end of the list yet. */
87 return xstrdup (default_shells[default_index++]);
91 if (shellstream == NULL)
93 shellstream = fopen (SHELLS_FILE, "r");
94 if (shellstream == NULL)
96 /* No shells file. Use the default list. */
98 return xstrdup (default_shells[0]);
102 while (readname (&line, &line_size, shellstream))
107 return NULL; /* End of file. */
110 /* Rewind the shells file. */
117 rewind (shellstream);
120 /* Close the shells file. */
127 fclose (shellstream);
132 /* Read a line from STREAM, removing any newline at the end.
133 Place the result in *NAME, which is malloc'd
134 and/or realloc'd as necessary and can start out NULL,
135 and whose size is passed and returned in *SIZE.
137 Return the number of bytes placed in *NAME
138 if some nonempty sequence was found, otherwise 0. */
141 readname (char **name, size_t *size, FILE *stream)
144 size_t name_index = 0;
146 /* Skip blank space. */
147 while ((c = getc (stream)) != EOF && isspace (c))
152 if (*size <= name_index)
153 *name = x2nrealloc (*name, size, sizeof **name);
154 if (c == EOF || isspace (c))
156 (*name)[name_index++] = c;
159 (*name)[name_index] = '\0';
169 while (s = getusershell ())