source: trunk/minix/lib/posix/_execvp.c@ 11

/*      execvp() - execute with PATH search and prepared arguments
 *                                                      Author: Kees J. Bot
 *                                                              21 Jan 1994
 */

#define _MINIX_SOURCE

#define nil 0
#define execve _execve
#define execvp _execvp
#define sbrk _sbrk
#define stat _stat
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/stat.h>

extern char * const **_penviron;        /* The default environment. */

int execvp(const char *file, char * const *argv)
/* Execute the file with a path search on $PATH, just like the shell.  The
 * search continues on the errors ENOENT (not there), and EACCES (file not
 * executable or leading directories protected.)
 * Unlike other execvp implementations there is no default path, and no shell
 * is started for scripts.  One is supposed to define $PATH, and use #!/bin/sh.
 */
{
        struct stat sb;
        const char *path;               /* $PATH */
        char *full;                     /* Full name to try. */
        char *f;
        size_t full_size;
        int err= ENOENT;                /* Error return on failure. */

        if (strchr(file, '/') != nil || (path= getenv("PATH")) == nil)
                path= "";

        /* Compute the maximum length the full name may have, and align. */
        full_size= strlen(path) + 1 + strlen(file) + 1 + sizeof(char *) - 1;
        full_size&= ~(sizeof(char *) - 1);

        /* Claim space. */
        if ((full= (char *) sbrk(full_size)) == (char *) -1) {
                errno= E2BIG;
                return -1;
        }

        /* For each directory in the path... */
        do {
                f= full;
                while (*path != 0 && *path != ':') *f++= *path++;

                if (f > full) *f++= '/';

                strcpy(f, file);

                /* Stat first, small speed-up, better for ptrace. */
                if (stat(full, &sb) == -1) continue;

                (void) execve(full, argv, *_penviron);

                /* Prefer more interesting errno values then "not there". */
                if (errno != ENOENT) err= errno;

                /* Continue only on some errors. */
                if (err != ENOENT && err != EACCES) break;
        } while (*path++ != 0);

        (void) sbrk(-full_size);
        errno= err;
        return -1;
}