lib/ansi/system.c

   1 /*
   2  * (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
   3  * See the copyright notice in the ACK home directory, in the file "Copyright".
   4  */
   5 /* $Header$ */
   6
   7 #if     defined(_POSIX_SOURCE)
   8 #include        <sys/types.h>
   9 #endif
  10 #include        <stdlib.h>
  11 #include        <signal.h>
  12 #include        <limits.h>
  13
  14 extern pid_t _fork(void);
  15 extern pid_t _wait(int *);
  16 extern void _exit(int);
  17 extern void _execve(const char *path, const char ** argv, const char ** envp);
  18 extern int _close(int);
  19
  20 #define FAIL    127
  21
  22 extern const char ***_penviron;
  23 static const char *exec_tab[] = {
  24         "sh",                   /* argv[0] */
  25         "-c",                   /* argument to the shell */
  26         NULL,                   /* to be filled with user command */
  27         NULL                    /* terminating NULL */
  28         };
  29
  30 int
  31 system(const char *str)
  32 {
  33         int pid, exitstatus, waitval;
  34         int i;
  35
  36         if ((pid = _fork()) < 0) return str ? -1 : 0;
  37
  38         if (pid == 0) {
  39                 for (i = 3; i <= OPEN_MAX; i++)
  40                         _close(i);
  41                 if (!str) str = "cd .";         /* just testing for a shell */
  42                 exec_tab[2] = str;              /* fill in command */
  43                 _execve("/bin/sh", exec_tab, *_penviron);
  44                 /* get here if execve fails ... */
  45                 _exit(FAIL);    /* see manual page */
  46         }
  47         while ((waitval = _wait(&exitstatus)) != pid) {
  48                 if (waitval == -1) break;
  49         }
  50         if (waitval == -1) {
  51                 /* no child ??? or maybe interrupted ??? */
  52                 exitstatus = -1;
  53         }
  54         if (!str) {
  55                 if (exitstatus == FAIL << 8)            /* execve() failed */
  56                         exitstatus = 0;
  57                 else exitstatus = 1;                    /* /bin/sh exists */
  58         }
  59         return exitstatus;
  60 }