BSD 4_3 release

[unix-history] / usr / src / lib / libc / gen / popen.c

/*
* Copyright (c) 1980 Regents of the University of California.
* All rights reserved.  The Berkeley software License Agreement
* specifies the terms and conditions for redistribution.
*/

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)popen.c     5.4 (Berkeley) 3/26/86";
#endif LIBC_SCCS and not lint

#include <stdio.h>
#include <signal.h>

#define tst(a,b)        (*mode == 'r'? (b) : (a))
#define RDR     0
#define WTR     1

extern  char *malloc();

static  int *popen_pid;
static  int nfiles;

FILE *
popen(cmd,mode)
       char *cmd;
       char *mode;
{
       int p[2];
       int myside, hisside, pid;

       if (nfiles <= 0)
               nfiles = getdtablesize();
       if (popen_pid == NULL) {
               popen_pid = (int *)malloc(nfiles * sizeof *popen_pid);
               if (popen_pid == NULL)
                       return (NULL);
               for (pid = 0; pid < nfiles; pid++)
                       popen_pid[pid] = -1;
       }
       if (pipe(p) < 0)
               return (NULL);
       myside = tst(p[WTR], p[RDR]);
       hisside = tst(p[RDR], p[WTR]);
       if ((pid = vfork()) == 0) {
               /* myside and hisside reverse roles in child */
               close(myside);
               if (hisside != tst(0, 1)) {
                       dup2(hisside, tst(0, 1));
                       close(hisside);
               }
               execl("/bin/sh", "sh", "-c", cmd, (char *)NULL);
               _exit(127);
       }
       if (pid == -1) {
               close(myside);
               close(hisside);
               return (NULL);
       }
       popen_pid[myside] = pid;
       close(hisside);
       return (fdopen(myside, mode));
}

pclose(ptr)
       FILE *ptr;
{
       int child, pid, status, omask;

       child = popen_pid[fileno(ptr)];
       popen_pid[fileno(ptr)] = -1;
       fclose(ptr);
       if (child == -1)
               return (-1);
       omask = sigblock(sigmask(SIGINT)|sigmask(SIGQUIT)|sigmask(SIGHUP));
       while ((pid = wait(&status)) != child && pid != -1)
               ;
       (void) sigsetmask(omask);
       return (pid == -1 ? -1 : status);
}