popen.c

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/*
 * popen - open a pipe
 */
/* $Header: /opt/proj/minix/cvsroot/src/lib/other/popen.c,v 1.1.1.1 2005/04/21 14:56:27 beng Exp $ */

#include        <sys/types.h>
#include        <limits.h>
#include        <errno.h>
#include        <signal.h>
#include        <stdio.h>

#if     defined(__BSD4_2)
union wait {
        int     w_status;
};
typedef union wait wait_arg;
#else
typedef int wait_arg;
#endif  /* __BSD4_2 */

#include        "../stdio/loc_incl.h"

#ifdef _ANSI
int _close(int d);
int _dup2(int oldd, int newd);          /* not present in System 5 */
int _execl(const char *name, const char *_arg, ... );
pid_t _fork(void);
int _pipe(int fildes[2]);
pid_t _wait(wait_arg *status);
void _exit(int status);
#endif

static int pids[OPEN_MAX];

FILE *
popen(command, type)
_CONST char *command;
_CONST char *type;
{
        int piped[2];
        int Xtype = *type == 'r' ? 0 : *type == 'w' ? 1 : 2;
        int pid;

        if (Xtype == 2 ||
            _pipe(piped) < 0 ||
            (pid = _fork()) < 0) return 0;
        
        if (pid == 0) {
                /* child */
                register int *p;

                for (p = pids; p < &pids[OPEN_MAX]; p++) {
                        if (*p) _close((int)(p - pids));
                }
                _close(piped[Xtype]);
                _dup2(piped[!Xtype], !Xtype);
                _close(piped[!Xtype]);
                _execl("/bin/sh", "sh", "-c", command, (char *) 0);
                _exit(127);     /* like system() ??? */
        }

        pids[piped[Xtype]] = pid;
        _close(piped[!Xtype]);
        return fdopen(piped[Xtype], type);
}

#if     defined(__BSD4_2)
#define ret_val status.w_status
#else
#define ret_val status
#endif

int
pclose(stream)
FILE *stream;
{
        int fd = fileno(stream);
        wait_arg status;
        int wret;

#ifdef _ANSI
        void (*intsave)(int) = signal(SIGINT, SIG_IGN);
        void (*quitsave)(int) = signal(SIGQUIT, SIG_IGN);
#else
        void (*intsave)() = signal(SIGINT, SIG_IGN);
        void (*quitsave)() = signal(SIGQUIT, SIG_IGN);
#endif
        fclose(stream);
        while ((wret = _wait(&status)) != -1) {
                if (wret == pids[fd]) break;
        }
        if (wret == -1) ret_val = -1;
        signal(SIGINT, intsave);
        signal(SIGQUIT, quitsave);
        pids[fd] = 0;
        return ret_val;
}

#if     defined(__USG)
int _dup(int fildes);

static int
_dup2(oldd, newd)
int oldd, newd;
{
        int i = 0, fd, tmp;
        int fdbuf[_NFILES];

        /* ignore the error on the close() */
        tmp = errno; (void) _close(newd); errno = tmp;
        while ((fd = _dup(oldd)) != newd) {
                if (fd == -1) break;
                fdbuf[i++] = fd;
        }
        tmp = errno;
        while (--i >= 0) {
                _close(fdbuf[i]);
        }
        errno = tmp;
        return -(fd == -1);
}
#endif  /* __USG */

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