execvp.c raw

   1  #include <stdlib.h>
   2  #include <string.h>
   3  #include <unistd.h>
   4  #include <errno.h>
   5  #include <limits.h>
   6  
   7  extern char **__environ;
   8  
   9  int __execvpe(const char *file, char *const argv[], char *const envp[])
  10  {
  11  	const char *p, *z, *path = getenv("PATH");
  12  	size_t l, k;
  13  	int seen_eacces = 0;
  14  
  15  	errno = ENOENT;
  16  	if (!*file) return -1;
  17  
  18  	if (strchr(file, '/'))
  19  		return execve(file, argv, envp);
  20  
  21  	if (!path) path = "/usr/local/bin:/bin:/usr/bin";
  22  	k = strnlen(file, NAME_MAX+1);
  23  	if (k > NAME_MAX) {
  24  		errno = ENAMETOOLONG;
  25  		return -1;
  26  	}
  27  	l = strnlen(path, PATH_MAX-1)+1;
  28  
  29  	for(p=path; ; p=z) {
  30  		char b[l+k+1];
  31  		z = __strchrnul(p, ':');
  32  		if (z-p >= l) {
  33  			if (!*z++) break;
  34  			continue;
  35  		}
  36  		memcpy(b, p, z-p);
  37  		b[z-p] = '/';
  38  		memcpy(b+(z-p)+(z>p), file, k+1);
  39  		execve(b, argv, envp);
  40  		switch (errno) {
  41  		case EACCES:
  42  			seen_eacces = 1;
  43  		case ENOENT:
  44  		case ENOTDIR:
  45  			break;
  46  		default:
  47  			return -1;
  48  		}
  49  		if (!*z++) break;
  50  	}
  51  	if (seen_eacces) errno = EACCES;
  52  	return -1;
  53  }
  54  
  55  int execvp(const char *file, char *const argv[])
  56  {
  57  	return __execvpe(file, argv, __environ);
  58  }
  59  
  60  weak_alias(__execvpe, execvpe);
  61