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Annotation of 43BSD/ucb/Mail/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: #ifndef lint
        !             8: static char *sccsid = "@(#)popen.c     5.2 (Berkeley) 6/21/85";
        !             9: #endif not lint
        !            10: 
        !            11: #include <stdio.h>
        !            12: #include <signal.h>
        !            13: #include <errno.h>
        !            14: #define        tst(a,b)        (*mode == 'r'? (b) : (a))
        !            15: #define        RDR     0
        !            16: #define        WTR     1
        !            17: static int     popen_pid[20];
        !            18: 
        !            19: #ifndef VMUNIX
        !            20: #define vfork  fork
        !            21: #endif VMUNIX
        !            22: #ifndef        SIGRETRO
        !            23: #define        sigchild()
        !            24: #endif
        !            25: 
        !            26: FILE *
        !            27: popen(cmd,mode)
        !            28: char   *cmd;
        !            29: char   *mode;
        !            30: {
        !            31:        int p[2];
        !            32:        register myside, hisside, pid;
        !            33: 
        !            34:        if(pipe(p) < 0)
        !            35:                return NULL;
        !            36:        myside = tst(p[WTR], p[RDR]);
        !            37:        hisside = tst(p[RDR], p[WTR]);
        !            38:        if((pid = vfork()) == 0) {
        !            39:                /* myside and hisside reverse roles in child */
        !            40:                sigchild();
        !            41:                close(myside);
        !            42:                dup2(hisside, tst(0, 1));
        !            43:                close(hisside);
        !            44:                execl("/bin/csh", "sh", "-c", cmd, 0);
        !            45:                _exit(1);
        !            46:        }
        !            47:        if(pid == -1)
        !            48:                return NULL;
        !            49:        popen_pid[myside] = pid;
        !            50:        close(hisside);
        !            51:        return(fdopen(myside, mode));
        !            52: }
        !            53: 
        !            54: pclose(ptr)
        !            55: FILE *ptr;
        !            56: {
        !            57:        register f, r;
        !            58:        int status, omask;
        !            59:        extern int errno;
        !            60: 
        !            61:        f = fileno(ptr);
        !            62:        fclose(ptr);
        !            63: # ifdef VMUNIX
        !            64:        omask = sigblock(sigmask(SIGINT)|sigmask(SIGQUIT)|sigmask(SIGHUP));
        !            65: # endif VMUNIX
        !            66:        while((r = wait(&status)) != popen_pid[f] && r != -1 && errno != EINTR)
        !            67:                ;
        !            68:        if(r == -1)
        !            69:                status = -1;
        !            70: # ifdef VMUNIX
        !            71:        sigsetmask(omask);
        !            72: # endif VMUNIX
        !            73:        return(status);
        !            74: }

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