misc/getusershell.c

   1 /*
   2  * Copyright (c) 1985, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 4. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  29
  30 #if defined(LIBC_SCCS) && !defined(lint)
  31 static char sccsid[] = "@(#)getusershell.c      8.1 (Berkeley) 6/4/93";
  32 #endif /* LIBC_SCCS and not lint */
  33
  34 #include <sys/param.h>
  35 #include <sys/file.h>
  36 #include <sys/stat.h>
  37 #include <stdio.h>
  38 #include <stdio_ext.h>
  39 #include <ctype.h>
  40 #include <stdlib.h>
  41 #include <unistd.h>
  42 #include <paths.h>
  43
  44 /*
  45  * Local shells should NOT be added here.  They should be added in
  46  * /etc/shells.
  47  */
  48
  49 /* NB: we do not initialize okshells here.  The initialization needs
  50    relocations.  These interfaces are used so rarely that this is not
  51    justified.  Instead explicitly initialize the array when it is
  52    used.  */
  53 #if 0
  54 static const char *const okshells[] = { _PATH_BSHELL, _PATH_CSHELL, NULL };
  55 #else
  56 static const char *okshells[3];
  57 #endif
  58 static char **curshell, **shells, *strings;
  59 static char **initshells (void) __THROW;
  60
  61 /*
  62  * Get a list of shells from _PATH_SHELLS, if it exists.
  63  */
  64 char *
  65 getusershell()
  66 {
  67         char *ret;
  68
  69         if (curshell == NULL)
  70                 curshell = initshells();
  71         ret = *curshell;
  72         if (ret != NULL)
  73                 curshell++;
  74         return (ret);
  75 }
  76
  77 void
  78 endusershell()
  79 {
  80
  81         free(shells);
  82         shells = NULL;
  83         free(strings);
  84         strings = NULL;
  85         curshell = NULL;
  86 }
  87
  88 void
  89 setusershell()
  90 {
  91
  92         curshell = initshells();
  93 }
  94
  95 static char **
  96 initshells()
  97 {
  98         register char **sp, *cp;
  99         register FILE *fp;
 100         struct stat64 statb;
 101         size_t flen;
 102
 103         free(shells);
 104         shells = NULL;
 105         free(strings);
 106         strings = NULL;
 107         if ((fp = fopen(_PATH_SHELLS, "rc")) == NULL)
 108                 goto init_okshells_noclose;
 109         if (fstat64(fileno(fp), &statb) == -1) {
 110         init_okshells:
 111                 (void)fclose(fp);
 112         init_okshells_noclose:
 113                 okshells[0] = _PATH_BSHELL;
 114                 okshells[1] = _PATH_CSHELL;
 115                 return (char **) okshells;
 116         }
 117         if (statb.st_size > ~(size_t)0 / sizeof (char *) * 3)
 118                 goto init_okshells;
 119         flen = statb.st_size + 3;
 120         if ((strings = malloc(flen)) == NULL)
 121                 goto init_okshells;
 122         shells = malloc(statb.st_size / 3 * sizeof (char *));
 123         if (shells == NULL) {
 124                 free(strings);
 125                 strings = NULL;
 126                 goto init_okshells;
 127         }
 128         sp = shells;
 129         cp = strings;
 130         while (fgets_unlocked(cp, flen - (cp - strings), fp) != NULL) {
 131                 while (*cp != '#' && *cp != '/' && *cp != '\0')
 132                         cp++;
 133                 if (*cp == '#' || *cp == '\0' || cp[1] == '\0')
 134                         continue;
 135                 *sp++ = cp;
 136                 while (!isspace(*cp) && *cp != '#' && *cp != '\0')
 137                         cp++;
 138                 *cp++ = '\0';
 139         }
 140         *sp = NULL;
 141         (void)fclose(fp);
 142         return (shells);
 143 }