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Annotation of researchv10dc/man/man3/popen.3, revision 1.1

1.1     ! root        1: .TH POPEN 3S
        !             2: .CT 2 comm_proc
        !             3: .SH NAME
        !             4: popen, ppopen, vepopen, pclose \(mi open a pipe to/from a process
        !             5: .SH SYNOPSIS
        !             6: .nf
        !             7: .B #include <stdio.h>
        !             8: .PP
        !             9: .B FILE *popen(command, type)
        !            10: .B char *command, *type;
        !            11: .PP
        !            12: .B FILE *ppopen(command, type)
        !            13: .B char *command, *type;
        !            14: .PP
        !            15: .B FILE *vepopen(command, type, args, env)
        !            16: .B char *command, *type, **args, **env;
        !            17: .PP
        !            18: .B int pclose(stream)
        !            19: .B FILE *stream;
        !            20: .fi
        !            21: .SH DESCRIPTION
        !            22: The first argument to
        !            23: .I popen
        !            24: is a pointer to a null-terminated string
        !            25: containing a command line for
        !            26: .IR sh (1).
        !            27: .I Type
        !            28: is as in
        !            29: .IR fopen (3).
        !            30: .I Popen
        !            31: creates a pipe between
        !            32: the calling process and
        !            33: the command and returns
        !            34: a stream pointer that
        !            35: can be used to write to the standard input
        !            36: of the command or to read from the standard output.
        !            37: .PP
        !            38: .I Ppopen
        !            39: uses the
        !            40: .B -p
        !            41: shell flag to restrict the environment of the shell.
        !            42: Both
        !            43: .I popen
        !            44: and
        !            45: .I ppopen
        !            46: set the effective userid to the real userid
        !            47: before calling the shell.
        !            48: .PP
        !            49: .I Vepopen
        !            50: has arguments akin to those of
        !            51: .I execve 
        !            52: (see
        !            53: .IR exec (2)):
        !            54: a file to be executed,
        !            55: a mode as above,
        !            56: a null-terminated vector of argument strings,
        !            57: and a null-terminated vector of environment strings.
        !            58: The shell is not called, and the effective userid is preserved.
        !            59: .PP
        !            60: A stream opened by these routines
        !            61: should be closed by
        !            62: .I pclose,
        !            63: which waits for the associated process to terminate
        !            64: and returns the exit status of the command.
        !            65: .PP
        !            66: Because the 
        !            67: .I command
        !            68: inherits open files, in particular standard input and output, a type
        !            69: .L
        !            70: "r"
        !            71: call may be used to insert a filter in the input, and type
        !            72: .L
        !            73: "w"
        !            74: in the output.
        !            75: .SH "SEE ALSO"
        !            76: .IR exec (2),
        !            77: .IR pipe (2),
        !            78: .IR fopen (3),
        !            79: .IR stdio (3),
        !            80: .IR system (3)
        !            81: .SH DIAGNOSTICS
        !            82: .I Popen
        !            83: returns a null pointer
        !            84: if files or processes cannot be created, or the Shell
        !            85: cannot be accessed.
        !            86: .PP
        !            87: .I Pclose
        !            88: returns \-1
        !            89: if there is
        !            90: no process to wait for.
        !            91: .SH BUGS
        !            92: Buffered reading before opening an input filter
        !            93: may leave the standard input of that filter mispositioned.
        !            94: Similar problems with an output filter may be
        !            95: forestalled by calling
        !            96: .IR fflush ;
        !            97: see
        !            98: .IR fopen (3).
        !            99: .br
        !           100: The resetting of the userid
        !           101: is probably gratuitous;
        !           102: it is there as a defense against incautious use
        !           103: of the routine by set-uid programs.
        !           104: .br
        !           105: I/O type
        !           106: .L
        !           107: "r+w"
        !           108: exists but is not useful.

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