lib/posix/_execvp.c

   1 /*      execvp() - execute with PATH search and prepared arguments
   2  *                                                      Author: Kees J. Bot
   3  *                                                              21 Jan 1994
   4  */
   5
   6 #define _MINIX_SOURCE
   7
   8 #define nil 0
   9 #define execve _execve
  10 #define execvp _execvp
  11 #define sbrk _sbrk
  12 #define stat _stat
  13 #include <stdlib.h>
  14 #include <string.h>
  15 #include <unistd.h>
  16 #include <errno.h>
  17 #include <sys/stat.h>
  18
  19 extern char * const **_penviron;        /* The default environment. */
  20
  21 int execvp(const char *file, char * const *argv)
  22 /* Execute the file with a path search on $PATH, just like the shell.  The
  23  * search continues on the errors ENOENT (not there), and EACCES (file not
  24  * executable or leading directories protected.)
  25  * Unlike other execvp implementations there is no default path, and no shell
  26  * is started for scripts.  One is supposed to define $PATH, and use #!/bin/sh.
  27  */
  28 {
  29         struct stat sb;
  30         const char *path;               /* $PATH */
  31         char *full;                     /* Full name to try. */
  32         char *f;
  33         size_t full_size;
  34         int err= ENOENT;                /* Error return on failure. */
  35
  36         if (strchr(file, '/') != nil || (path= getenv("PATH")) == nil)
  37                 path= "";
  38
  39         /* Compute the maximum length the full name may have, and align. */
  40         full_size= strlen(path) + 1 + strlen(file) + 1 + sizeof(char *) - 1;
  41         full_size&= ~(sizeof(char *) - 1);
  42
  43         /* Claim space. */
  44         if ((full= (char *) sbrk(full_size)) == (char *) -1) {
  45                 errno= E2BIG;
  46                 return -1;
  47         }
  48
  49         /* For each directory in the path... */
  50         do {
  51                 f= full;
  52                 while (*path != 0 && *path != ':') *f++= *path++;
  53
  54                 if (f > full) *f++= '/';
  55
  56                 strcpy(f, file);
  57
  58                 /* Stat first, small speed-up, better for ptrace. */
  59                 if (stat(full, &sb) == -1) continue;
  60
  61                 (void) execve(full, argv, *_penviron);
  62
  63                 /* Prefer more interesting errno values then "not there". */
  64                 if (errno != ENOENT) err= errno;
  65
  66                 /* Continue only on some errors. */
  67                 if (err != ENOENT && err != EACCES) break;
  68         } while (*path++ != 0);
  69
  70         (void) sbrk(-full_size);
  71         errno= err;
  72         return -1;
  73 }