posix/execvp.c

   1 /* Copyright (C) 1991, 92, 95, 96, 97, 98 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Library General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Library General Public License for more details.
  13
  14    You should have received a copy of the GNU Library General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #include <unistd.h>
  20 #include <stdarg.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <errno.h>
  24 #include <paths.h>
  25
  26
  27 static void
  28 internal_function
  29 execute (const char *file, char *const argv[])
  30 {
  31   execv (file, argv);
  32
  33   if (errno == ENOEXEC)
  34     {
  35       /* The file is accessible but it is not an executable file.
  36          Invoke the shell to interpret it as a script.  */
  37
  38       /* Count the arguments.  */
  39       int argc = 0;
  40       while (argv[argc++])
  41         ;
  42
  43       /* Construct an argument list for the shell.  */
  44       {
  45         char *new_argv[argc + 1];
  46         new_argv[0] = (char *) _PATH_BSHELL;
  47         new_argv[1] = (char *) file;
  48         while (argc > 1)
  49           {
  50             new_argv[argc] = argv[argc - 1];
  51             --argc;
  52           }
  53
  54         /* Execute the shell.  */
  55         execv (new_argv[0], new_argv);
  56       }
  57     }
  58 }
  59
  60
  61 /* Execute FILE, searching in the `PATH' environment variable if it contains
  62    no slashes, with arguments ARGV and environment from `environ'.  */
  63 int
  64 execvp (file, argv)
  65      const char *file;
  66      char *const argv[];
  67 {
  68   int got_eacces = 0;
  69
  70   if (*file == '\0')
  71     {
  72       /* We check the simple case first. */
  73       __set_errno (ENOENT);
  74       return -1;
  75     }
  76
  77   if (strchr (file, '/') != NULL)
  78     /* Don't search when it contains a slash.  */
  79     execute (file, argv);
  80   else
  81     {
  82       char *path, *p, *name;
  83       size_t len;
  84
  85       path = getenv ("PATH");
  86       if (path == NULL)
  87         {
  88           /* There is no `PATH' in the environment.
  89              The default search path is the current directory
  90              followed by the path `confstr' returns for `_CS_PATH'.  */
  91           len = confstr (_CS_PATH, (char *) NULL, 0);
  92           path = (char *) __alloca (1 + len);
  93           path[0] = ':';
  94           (void) confstr (_CS_PATH, path + 1, len);
  95         }
  96
  97       len = strlen (file) + 1;
  98       name = __alloca (strlen (path) + len);
  99       p = path;
 100       do
 101         {
 102           path = p;
 103           p = strchr (path, ':');
 104           if (p == NULL)
 105             p = strchr (path, '\0');
 106
 107           if (p == path)
 108             /* Two adjacent colons, or a colon at the beginning or the end
 109                of `PATH' means to search the current directory.  */
 110             (void) memcpy (name, file, len);
 111           else
 112             {
 113               /* Construct the pathname to try.  */
 114               char *tmp = __mempcpy (name, path, p - path);
 115               *tmp++ = '/';
 116               (void) __mempcpy (tmp, file, len);
 117             }
 118
 119           /* Try to execute this name.  If it works, execv will not return.  */
 120           execute (name, argv);
 121
 122           switch (errno)
 123             {
 124             case EACCES:
 125               /* Record the we got a `Permission denied' error.  If we end
 126                  up finding no executable we can use, we want to diagnose
 127                  that we did find one but were denied access.  */
 128               got_eacces = 1;
 129             case ENOENT:
 130             case ESTALE:
 131             case ENOTDIR:
 132               /* Those errors indicate the file is missing or not executable
 133                  by us, in which case we want to just try the next path
 134                  directory.  */
 135               break;
 136
 137             default:
 138               /* Some other error means we found an executable file, but
 139                  something went wrong executing it; return the error to our
 140                  caller.  */
 141               return -1;
 142             }
 143         }
 144       while (*p++ != '\0');
 145     }
 146
 147   /* We tried every element and none of them worked.  */
 148
 149   if (got_eacces)
 150     /* At least one failure was due to permissions, so report that error.  */
 151     __set_errno (EACCES);
 152
 153   /* Return the error from the last attempt (probably ENOENT).  */
 154   return -1;
 155 }