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Annotation of 43BSD/lib/libc/gen/popen.c, revision 1.1

1.1     ! root        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: }

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