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 static const char *okshells[] = { _PATH_BSHELL, _PATH_CSHELL, NULL };
  50 static char **curshell, **shells, *strings;
  51 static char **initshells (void) __THROW;
  52
  53 /*
  54  * Get a list of shells from _PATH_SHELLS, if it exists.
  55  */
  56 char *
  57 getusershell()
  58 {
  59         char *ret;
  60
  61         if (curshell == NULL)
  62                 curshell = initshells();
  63         ret = *curshell;
  64         if (ret != NULL)
  65                 curshell++;
  66         return (ret);
  67 }
  68
  69 void
  70 endusershell()
  71 {
  72
  73         if (shells != NULL)
  74                 free(shells);
  75         shells = NULL;
  76         if (strings != NULL)
  77                 free(strings);
  78         strings = NULL;
  79         curshell = NULL;
  80 }
  81
  82 void
  83 setusershell()
  84 {
  85
  86         curshell = initshells();
  87 }
  88
  89 static char **
  90 initshells()
  91 {
  92         register char **sp, *cp;
  93         register FILE *fp;
  94         struct stat64 statb;
  95         int flen;
  96
  97         if (shells != NULL)
  98                 free(shells);
  99         shells = NULL;
 100         if (strings != NULL)
 101                 free(strings);
 102         strings = NULL;
 103         if ((fp = fopen(_PATH_SHELLS, "rc")) == NULL)
 104                 return (char **) okshells;
 105         if (fstat64(fileno(fp), &statb) == -1) {
 106                 (void)fclose(fp);
 107                 return (char **) okshells;
 108         }
 109         if ((strings = malloc((u_int)statb.st_size + 1)) == NULL) {
 110                 (void)fclose(fp);
 111                 return (char **) okshells;
 112         }
 113         shells = calloc((unsigned)statb.st_size / 3, sizeof (char *));
 114         if (shells == NULL) {
 115                 (void)fclose(fp);
 116                 free(strings);
 117                 strings = NULL;
 118                 return (char **) okshells;
 119         }
 120         /* No threads using this stream.  */
 121         __fsetlocking (fp, FSETLOCKING_BYCALLER);
 122         sp = shells;
 123         cp = strings;
 124         flen = statb.st_size;
 125         while (fgets_unlocked(cp, flen - (cp - strings), fp) != NULL) {
 126                 while (*cp != '#' && *cp != '/' && *cp != '\0')
 127                         cp++;
 128                 if (*cp == '#' || *cp == '\0')
 129                         continue;
 130                 *sp++ = cp;
 131                 while (!isspace(*cp) && *cp != '#' && *cp != '\0')
 132                         cp++;
 133                 *cp++ = '\0';
 134         }
 135         *sp = NULL;
 136         (void)fclose(fp);
 137         return (shells);
 138 }