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Annotation of 41BSD/libc/stdio/popen.c, revision 1.1

1.1     ! root        1: #include <stdio.h>
        !             2: #include <signal.h>
        !             3: #define        tst(a,b)        (*mode == 'r'? (b) : (a))
        !             4: #define        RDR     0
        !             5: #define        WTR     1
        !             6: static int     popen_pid[20];
        !             7: 
        !             8: FILE *
        !             9: popen(cmd,mode)
        !            10: char   *cmd;
        !            11: char   *mode;
        !            12: {
        !            13:        int p[2];
        !            14:        register myside, hisside, pid;
        !            15: 
        !            16:        if(pipe(p) < 0)
        !            17:                return NULL;
        !            18:        myside = tst(p[WTR], p[RDR]);
        !            19:        hisside = tst(p[RDR], p[WTR]);
        !            20:        if((pid = vfork()) == 0) {
        !            21:                /* myside and hisside reverse roles in child */
        !            22:                close(myside);
        !            23:                dup2(hisside, tst(0, 1));
        !            24:                close(hisside);
        !            25:                execl("/bin/sh", "sh", "-c", cmd, 0);
        !            26:                _exit(1);
        !            27:        }
        !            28:        if(pid == -1)
        !            29:                return NULL;
        !            30:        popen_pid[myside] = pid;
        !            31:        close(hisside);
        !            32:        return(fdopen(myside, mode));
        !            33: }
        !            34: 
        !            35: pclose(ptr)
        !            36: FILE *ptr;
        !            37: {
        !            38:        register f, r, (*hstat)(), (*istat)(), (*qstat)();
        !            39:        int status;
        !            40: 
        !            41:        f = fileno(ptr);
        !            42:        fclose(ptr);
        !            43:        istat = signal(SIGINT, SIG_IGN);
        !            44:        qstat = signal(SIGQUIT, SIG_IGN);
        !            45:        hstat = signal(SIGHUP, SIG_IGN);
        !            46:        while((r = wait(&status)) != popen_pid[f] && r != -1)
        !            47:                ;
        !            48:        if(r == -1)
        !            49:                status = -1;
        !            50:        signal(SIGINT, istat);
        !            51:        signal(SIGQUIT, qstat);
        !            52:        signal(SIGHUP, hstat);
        !            53:        return(status);
        !            54: }

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