date and time created 89/05/17 22:49:21 by bostic

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

/*
* Copyright (c) 1988 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software written by Ken Arnold and
* published in UNIX Review, Vol. 6, No. 8.
*
* Redistribution and use in source and binary forms are permitted
* provided that the above copyright notice and this paragraph are
* duplicated in all such forms and that any documentation,
* advertising materials, and other materials related to such
* distribution and use acknowledge that the software was developed
* by the University of California, Berkeley.  The name of the
* University may not be used to endorse or promote products derived
* from this software without specific prior written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)popen.c     5.9 (Berkeley) %G%";
#endif /* LIBC_SCCS and not lint */

#include <sys/param.h>
#include <sys/signal.h>
#include <sys/wait.h>
#include <stdio.h>

static pid_t *pids;
static int fds;

FILE *
popen(program, type)
       char *program, *type;
{
       FILE *iop;
       int pdes[2], pid;
       char *malloc();

       if (*type != 'r' && *type != 'w' || type[1])
               return(NULL);

       if (pids == NULL) {
               if ((fds = getdtablesize()) <= 0)
                       return(NULL);
               if ((pids = (pid_t *)malloc((u_int)(fds * sizeof(int)))) == NULL)
                       return(NULL);
               bzero((char *)pids, fds * sizeof(pid_t));
       }
       if (pipe(pdes) < 0)
               return(NULL);
       switch (pid = vfork()) {
       case -1:                        /* error */
               (void)close(pdes[0]);
               (void)close(pdes[1]);
               return(NULL);
               /* NOTREACHED */
       case 0:                         /* child */
               if (*type == 'r') {
                       if (pdes[1] != 1) {
                               dup2(pdes[1], 1);
                               (void)close(pdes[1]);
                       }
                       (void)close(pdes[0]);
               } else {
                       if (pdes[0] != 0) {
                               dup2(pdes[0], 0);
                               (void)close(pdes[0]);
                       }
                       (void)close(pdes[1]);
               }
               execl("/bin/sh", "sh", "-c", program, NULL);
               _exit(127);
               /* NOTREACHED */
       }
       /* parent; assume fdopen can't fail...  */
       if (*type == 'r') {
               iop = fdopen(pdes[0], type);
               (void)close(pdes[1]);
       } else {
               iop = fdopen(pdes[1], type);
               (void)close(pdes[0]);
       }
       pids[fileno(iop)] = pid;
       return(iop);
}

pclose(iop)
       FILE *iop;
{
       register int fdes;
       int omask;
       union wait pstat;
       pid_t pid, waitpid();

       /*
        * pclose returns -1 if stream is not associated with a
        * `popened' command, if already `pclosed', or waitpid
        * returns an error.
        */
       if (pids == NULL || pids[fdes = fileno(iop)] == 0)
               return(-1);
       (void)fclose(iop);
       omask = sigblock(sigmask(SIGINT)|sigmask(SIGQUIT)|sigmask(SIGHUP));
       pid = waitpid(pids[fdes], &pstat, 0);
       (void)sigsetmask(omask);
       pids[fdes] = 0;
       return(pid == -1 ? -1 : pstat.w_status);
}