4.3BSD - /usr/src/lib/libc/gen/popen.c

   1: /*
   2:  * Copyright (c) 1980 Regents of the University of California.
   3:  * All rights reserved.  The Berkeley software License Agreement
   4:  * specifies the terms and conditions for redistribution.
   5:  */
   6: 
   7: #if defined(LIBC_SCCS) && !defined(lint)
   8: static char sccsid[] = "@(#)popen.c	5.4 (Berkeley) 3/26/86";
   9: #endif LIBC_SCCS and not lint
  10: 
  11: #include <stdio.h>
  12: #include <signal.h>
  13: 
  14: #define tst(a,b)    (*mode == 'r'? (b) : (a))
  15: #define RDR 0
  16: #define WTR 1
  17: 
  18: extern  char *malloc();
  19: 
  20: static  int *popen_pid;
  21: static  int nfiles;
  22: 
  23: FILE *
  24: popen(cmd,mode)
  25:     char *cmd;
  26:     char *mode;
  27: {
  28:     int p[2];
  29:     int myside, hisside, pid;
  30: 
  31:     if (nfiles <= 0)
  32:         nfiles = getdtablesize();
  33:     if (popen_pid == NULL) {
  34:         popen_pid = (int *)malloc(nfiles * sizeof *popen_pid);
  35:         if (popen_pid == NULL)
  36:             return (NULL);
  37:         for (pid = 0; pid < nfiles; pid++)
  38:             popen_pid[pid] = -1;
  39:     }
  40:     if (pipe(p) < 0)
  41:         return (NULL);
  42:     myside = tst(p[WTR], p[RDR]);
  43:     hisside = tst(p[RDR], p[WTR]);
  44:     if ((pid = vfork()) == 0) {
  45:         /* myside and hisside reverse roles in child */
  46:         close(myside);
  47:         if (hisside != tst(0, 1)) {
  48:             dup2(hisside, tst(0, 1));
  49:             close(hisside);
  50:         }
  51:         execl("/bin/sh", "sh", "-c", cmd, (char *)NULL);
  52:         _exit(127);
  53:     }
  54:     if (pid == -1) {
  55:         close(myside);
  56:         close(hisside);
  57:         return (NULL);
  58:     }
  59:     popen_pid[myside] = pid;
  60:     close(hisside);
  61:     return (fdopen(myside, mode));
  62: }
  63: 
  64: pclose(ptr)
  65:     FILE *ptr;
  66: {
  67:     int child, pid, status, omask;
  68: 
  69:     child = popen_pid[fileno(ptr)];
  70:     popen_pid[fileno(ptr)] = -1;
  71:     fclose(ptr);
  72:     if (child == -1)
  73:         return (-1);
  74:     omask = sigblock(sigmask(SIGINT)|sigmask(SIGQUIT)|sigmask(SIGHUP));
  75:     while ((pid = wait(&status)) != child && pid != -1)
  76:         ;
  77:     (void) sigsetmask(omask);
  78:     return (pid == -1 ? -1 : status);
  79: }

Defined functions

Defined variables

Defined macros