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Annotation of 43BSDReno/lib/libc/gen/popen.3, revision 1.1

1.1     ! root        1: .\"    @(#)popen.3     6.2 (Berkeley) 12/7/88
        !             2: .\"
        !             3: .TH POPEN 3 "December 7, 1988"
        !             4: .AT 3
        !             5: .SH NAME
        !             6: popen, pclose \- initiate I/O to/from a process
        !             7: .SH SYNOPSIS
        !             8: .B #include <stdio.h>
        !             9: .PP
        !            10: .SM
        !            11: .B FILE
        !            12: .B *popen(command, type)
        !            13: .br
        !            14: .B char *command, *type;
        !            15: .PP
        !            16: .B pclose(stream)
        !            17: .br
        !            18: .SM
        !            19: .B FILE
        !            20: .B *stream;
        !            21: .SH DESCRIPTION
        !            22: The arguments to 
        !            23: .I popen
        !            24: are pointers to null-terminated strings containing respectively a
        !            25: shell command line and an I/O mode, either "r" for reading or "w" for
        !            26: writing.  It creates a pipe between the calling process and
        !            27: the command to be executed.  The value returned is a stream pointer that
        !            28: can be used (as appropriate) to write to the standard input
        !            29: of the command or read from its standard output.
        !            30: .PP
        !            31: A stream opened by
        !            32: .I popen
        !            33: should be closed by
        !            34: .IR pclose ,
        !            35: which waits for the associated process to terminate
        !            36: and returns the exit status of the command.
        !            37: .PP
        !            38: Because open files are shared, a type "r" command may be used as an input
        !            39: filter, and a type "w" as an output filter.
        !            40: .SH "SEE ALSO"
        !            41: sh(1), pipe(2), wait4(2), fclose(3), fopen(3), system(3)
        !            42: .SH DIAGNOSTICS
        !            43: .I Popen
        !            44: returns a null pointer if files or processes cannot be created, or the shell 
        !            45: cannot be accessed.
        !            46: .PP
        !            47: .I Pclose
        !            48: returns \-1 if
        !            49: .I stream
        !            50: is not associated with a `popened' command, or if
        !            51: .I stream
        !            52: already `pclosed', or
        !            53: .IR wait (4)
        !            54: returns an error.
        !            55: .SH BUGS
        !            56: Buffered reading before opening an input filter
        !            57: may leave the standard input of that filter mispositioned.
        !            58: Similar problems with an output filter may be
        !            59: forestalled by careful buffer flushing, for instance, with
        !            60: .I fflush,
        !            61: see
        !            62: .IR fclose (3).
        !            63: .LP
        !            64: .I Popen
        !            65: always calls
        !            66: .IR sh ,
        !            67: never calls
        !            68: .IR csh .

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