52 lines
1.4 KiB
Groff
52 lines
1.4 KiB
Groff
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.\" @(#)popen.3 6.1 (Berkeley) 5/15/85
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.\"
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.TH POPEN 3 "May 15, 1985"
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.AT 3
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.SH NAME
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popen, pclose \- initiate I/O to/from a process
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.SH SYNOPSIS
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.nf
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.ft B
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#include <stdio.h>
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FILE *popen(const char *command, const char *type)
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int pclose(FILE *stream)
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.SH DESCRIPTION
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The arguments to
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.B popen
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are pointers to null-terminated strings containing respectively a
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shell command line and an I/O mode, either "r" for reading or "w" for
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writing. It creates a pipe between the calling process and
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the command to be executed. The value returned is a stream pointer that
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can be used (as appropriate) to write to the standard input
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of the command or read from its standard output.
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.PP
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A stream opened by
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.B popen
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should be closed by
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.BR pclose ,
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which waits for the associated process to terminate
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and returns the exit status of the command.
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.PP
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Because open files are shared, a type "r" command may be used as an input
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filter, and a type "w" as an output filter.
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.SH "SEE ALSO"
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.BR pipe (2),
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.BR fopen (3),
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.BR fclose (3),
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.BR system (3),
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.BR wait (2),
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.BR sh (1).
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.SH DIAGNOSTICS
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.B Popen
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returns a null pointer if files or processes cannot be created, or the shell
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cannot be accessed.
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.SH BUGS
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Buffered reading before opening an input filter
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may leave the standard input of that filter mispositioned.
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Similar problems with an output filter may be
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forestalled by careful buffer flushing, for instance, with
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.BR fflush ,
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see
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.BR fclose (3).
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