NAME
Tcl_CreatePipeline - create one or more child processes, with I/O redirection
SYNOPSIS
#include <tcl.h>
int
Tcl_CreatePipeline(interp, argc, argv, pidArrayPtr, inPipePtr, outPipePtr, errFilePtr)
ARGUMENTS
-
Tcl_Interp *interp (in)
-
Interpreter to use for error reporting.
-
int argc (in)
-
Number of strings in argv array.
-
char **argv (in)
-
Array of strings describing command(s) and I/O redirection.
-
int **pidArrayPtr (out)
-
The value at *pidArrayPtr is modified to hold a pointer to
an array of process identifiers. The array is dynamically
allocated and must be freed by the caller.
-
char *inPipePtr (out)
-
If this argument is NULL then standard input for the first command
in the pipeline comes from the current standard input.
If inPipePtr is not NULL then Tcl_CreatePipeline will
create a pipe, arrange for it to be used for standard input
to the first command,
and store a file id for writing to that pipe at *inPipePtr.
If the command specified its own input using redirection, then
no pipe is created and -1 is stored at *inPipePtr.
-
char *outPipePtr (out)
-
If this argument is NULL then standard output for the last command
in the pipeline goes to the current standard output.
If outPipePtr is not NULL then Tcl_CreatePipeline will
create a pipe, arrange for it to be used for standard output from
the last command, and store a file id for reading from that
pipe at *outPipePtr.
If the command specified its own output using redirection then
no pipe is created and -1 is stored at *outPipePtr.
-
char *errFilePtr (out)
-
If this argument is NULL then error output for all the commands
in the pipeline will go to the current standard error file.
If errFilePtr is not NULL, error output from all the commands
in the pipeline will go to a temporary file created by
Tcl_CreatePipeline.
A file id to read from that file will be stored at *errFilePtr.
The file will already have been removed, so closing the file
descriptor at *errFilePtr will cause the file to be flushed
completely.
DESCRIPTION
Tcl_CreatePipeline processes the argv array and sets
up one or more child processes in a pipeline configuration.
Tcl_CreatePipeline handles pipes specified with ``|'',
input redirection specified with ``<'' or ``<<'', and output
redirection specified with ``>''; see the documentation for
the exec command for details on these specifications.
The return value from Tcl_CreatePipeline is a count of
the number of child processes created; the process identifiers
for those processes are stored in a malloc-ed array and
a pointer to that array is stored at *pidArrayPtr.
It is the caller's responsibility to free the array when finished
with it.
If the inPipePtr, outPipePtr, and errFilePtr
arguments are NULL then the pipeline's standard input, standard
output, and standard error are taken from the corresponding
streams of the process. Non-NULL values may be specified for
these arguments to use pipes for standard input and standard
output and a file for standard error. Tcl_CreatePipeline
will create the requested pipes or file and return file identifiers
that may be used to read or write them. It is the caller's
responsibility to close all of these files when they are no
longer needed. If argv specifies redirection for standard
input or standard output, then pipes will not be created even
if requested by the inPipePtr and outPipePtr
arguments.
If an error occurs in Tcl_CreatePipeline (e.g. ``|'' or
``<'' was the last argument in argv, or it wasn't possible
to fork off a child), then -1 is returned
and interp->result is set to an error message.
SEE ALSO
Tcl_WaitPids, Tcl_DetachPids
KEYWORDS
background, child, detach, fork, process, status, wait
[ tinytcl ]
Copyright © 1989-1994 The Regents of the University of California.
Copyright © 1994-1996 Sun Microsystems, Inc.
