BSD 4_3 release

[unix-history] / usr / src / ucb / Mail / 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.
*/

#ifndef lint
static char *sccsid = "@(#)popen.c      5.2 (Berkeley) 6/21/85";
#endif not lint

#include <stdio.h>
#include <signal.h>
#include <errno.h>
#define tst(a,b)        (*mode == 'r'? (b) : (a))
#define RDR     0
#define WTR     1
static  int     popen_pid[20];

#ifndef VMUNIX
#define vfork   fork
#endif VMUNIX
#ifndef SIGRETRO
#define sigchild()
#endif

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

       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 */
               sigchild();
               close(myside);
               dup2(hisside, tst(0, 1));
               close(hisside);
               execl("/bin/csh", "sh", "-c", cmd, 0);
               _exit(1);
       }
       if(pid == -1)
               return NULL;
       popen_pid[myside] = pid;
       close(hisside);
       return(fdopen(myside, mode));
}

pclose(ptr)
FILE *ptr;
{
       register f, r;
       int status, omask;
       extern int errno;

       f = fileno(ptr);
       fclose(ptr);
# ifdef VMUNIX
       omask = sigblock(sigmask(SIGINT)|sigmask(SIGQUIT)|sigmask(SIGHUP));
# endif VMUNIX
       while((r = wait(&status)) != popen_pid[f] && r != -1 && errno != EINTR)
               ;
       if(r == -1)
               status = -1;
# ifdef VMUNIX
       sigsetmask(omask);
# endif VMUNIX
       return(status);
}