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.\" ========================================================================
.\"
.IX Title "IPC::Run3 3"
.TH IPC::Run3 3 2024-01-28 "perl v5.38.1" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH NAME
IPC::Run3 \- run a subprocess with input/output redirection
.SH VERSION
.IX Header "VERSION"
version 0.049
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\&    use IPC::Run3;    # Exports run3() by default
\&
\&    run3 \e@cmd, \e$in, \e$out, \e$err;
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
This module allows you to run a subprocess and redirect stdin, stdout,
and/or stderr to files and perl data structures.  It aims to satisfy 99% of the
need for using \f(CW\*(C`system\*(C'\fR, \f(CW\*(C`qx\*(C'\fR, and \f(CW\*(C`open3\*(C'\fR
with a simple, extremely Perlish API.
.PP
Speed, simplicity, and portability are paramount.  (That's speed of Perl code;
which is often much slower than the kind of buffered I/O that this module uses
to spool input to and output from the child command.)
.ie n .SS """run3($cmd, $stdin, $stdout, $stderr, \e%options)"""
.el .SS "\f(CWrun3($cmd, $stdin, $stdout, $stderr, \e%options)\fP"
.IX Subsection "run3($cmd, $stdin, $stdout, $stderr, %options)"
All parameters after \f(CW$cmd\fR are optional.
.PP
The parameters \f(CW$stdin\fR, \f(CW$stdout\fR and \f(CW$stderr\fR indicate how the child's
corresponding filehandle (\f(CW\*(C`STDIN\*(C'\fR, \f(CW\*(C`STDOUT\*(C'\fR and \f(CW\*(C`STDERR\*(C'\fR, resp.) will be
redirected.  Because the redirects come last, this allows \f(CW\*(C`STDOUT\*(C'\fR and
\&\f(CW\*(C`STDERR\*(C'\fR to default to the parent's by just not specifying them \-\- a common
use case.
.PP
\&\f(CW\*(C`run3\*(C'\fR throws an exception if the wrapped \f(CW\*(C`system\*(C'\fR call returned \-1 or
anything went wrong with \f(CW\*(C`run3\*(C'\fR's processing of filehandles.  Otherwise it
returns true.  It leaves \f(CW$?\fR intact for inspection of exit and wait status.
.PP
Note that a true return value from \f(CW\*(C`run3\*(C'\fR doesn't mean that the command had a
successful exit code. Hence you should always check \f(CW$?\fR.
.PP
See "%options" for an option to handle the case of \f(CW\*(C`system\*(C'\fR returning \-1
yourself.
.PP
\fR\f(CI$cmd\fR\fI\fR
.IX Subsection "$cmd"
.PP
Usually \f(CW$cmd\fR will be an ARRAY reference and the child is invoked via
.PP
.Vb 1
\&  system @$cmd;
.Ve
.PP
But \f(CW$cmd\fR may also be a string in which case the child is invoked via
.PP
.Vb 1
\&  system $cmd;
.Ve
.PP
(cf. "system" in perlfunc for the difference and the pitfalls of using
the latter form).
.PP
\fR\f(CI$stdin\fR\fI, \fR\f(CI$stdout\fR\fI, \fR\f(CI$stderr\fR\fI\fR
.IX Subsection "$stdin, $stdout, $stderr"
.PP
The parameters \f(CW$stdin\fR, \f(CW$stdout\fR and \f(CW$stderr\fR can take one of the
following forms:
.ie n .IP """undef"" (or not specified at all)" 4
.el .IP "\f(CWundef\fR (or not specified at all)" 4
.IX Item "undef (or not specified at all)"
The child inherits the corresponding filehandle from the parent.
.Sp
.Vb 2
\&  run3 \e@cmd, $stdin;                   # child writes to same STDOUT and STDERR as parent
\&  run3 \e@cmd, undef, $stdout, $stderr;  # child reads from same STDIN as parent
.Ve
.ie n .IP """\eundef""" 4
.el .IP \f(CW\eundef\fR 4
.IX Item "undef"
The child's filehandle is redirected from or to the local equivalent of
\&\f(CW\*(C`/dev/null\*(C'\fR (as returned by \f(CW\*(C`File::Spec\->devnull()\*(C'\fR).
.Sp
.Vb 1
\&  run3 \e@cmd, \eundef, $stdout, $stderr; # child reads from /dev/null
.Ve
.IP "a simple scalar" 4
.IX Item "a simple scalar"
The parameter is taken to be the name of a file to read from
or write to. In the latter case, the file will be opened via
.Sp
.Vb 1
\&  open FH, ">", ...
.Ve
.Sp
i.e. it is created if it doesn't exist and truncated otherwise.
Note that the file is opened by the parent which will croak
in case of failure.
.Sp
.Vb 1
\&  run3 \e@cmd, \eundef, "out.txt";        # child writes to file "out.txt"
.Ve
.ie n .IP "a filehandle (either a reference to a GLOB or an ""IO::Handle"")" 4
.el .IP "a filehandle (either a reference to a GLOB or an \f(CWIO::Handle\fR)" 4
.IX Item "a filehandle (either a reference to a GLOB or an IO::Handle)"
The filehandle is inherited by the child.
.Sp
.Vb 7
\&  open my $fh, ">", "out.txt";
\&  print $fh "prologue\en";
\&  ...
\&  run3 \e@cmd, \eundef, $fh;              # child writes to $fh
\&  ...
\&  print $fh "epilogue\en";
\&  close $fh;
.Ve
.IP "a SCALAR reference" 4
.IX Item "a SCALAR reference"
The referenced scalar is treated as a string to be read from or
written to. In the latter case, the previous content of the string
is overwritten.
.Sp
.Vb 7
\&  my $out;
\&  run3 \e@cmd, \eundef, \e$out;           # child writes into string
\&  run3 \e@cmd, \e<<EOF;                  # child reads from string (can use "here" notation)
\&  Input
\&  to
\&  child
\&  EOF
.Ve
.IP "an ARRAY reference" 4
.IX Item "an ARRAY reference"
For \f(CW$stdin\fR, the elements of \f(CW@$stdin\fR are simply spooled to the child.
.Sp
For \f(CW$stdout\fR or \f(CW$stderr\fR, the child's corresponding file descriptor
is read line by line (as determined by the current setting of \f(CW$/\fR)
into \f(CW@$stdout\fR or \f(CW@$stderr\fR, resp. The previous content of the array
is overwritten.
.Sp
.Vb 2
\&  my @lines;
\&  run3 \e@cmd, \eundef, \e@lines;         # child writes into array
.Ve
.IP "a CODE reference" 4
.IX Item "a CODE reference"
For \f(CW$stdin\fR, \f(CW&$stdin\fR will be called repeatedly (with no arguments) and
the return values are spooled to the child. \f(CW&$stdin\fR must signal the end of
input by returning \f(CW\*(C`undef\*(C'\fR.
.Sp
For \f(CW$stdout\fR or \f(CW$stderr\fR, the child's corresponding file descriptor
is read line by line (as determined by the current setting of \f(CW$/\fR)
and \f(CW&$stdout\fR or \f(CW&$stderr\fR, resp., is called with the contents of the line.
Note that there's no end-of-file indication.
.Sp
.Vb 4
\&  my $i = 0;
\&  sub producer {
\&    return $i < 10 ? "line".$i++."\en" : undef;
\&  }
\&
\&  run3 \e@cmd, \e&producer;              # child reads 10 lines
.Ve
.Sp
Note that this form of redirecting the child's I/O doesn't imply
any form of concurrency between parent and child \- \fBrun3()\fR's method of
operation is the same no matter which form of redirection you specify.
.PP
If the same value is passed for \f(CW$stdout\fR and \f(CW$stderr\fR, then the child
will write both \f(CW\*(C`STDOUT\*(C'\fR and \f(CW\*(C`STDERR\*(C'\fR to the same filehandle.
In general, this means that
.PP
.Vb 2
\&    run3 \e@cmd, \eundef, "foo.txt", "foo.txt";
\&    run3 \e@cmd, \eundef, \e$both, \e$both;
.Ve
.PP
will DWIM and pass a single file handle to the child for both \f(CW\*(C`STDOUT\*(C'\fR and
\&\f(CW\*(C`STDERR\*(C'\fR, collecting all into file "foo.txt" or \f(CW$both\fR.
.PP
\fR\f(CI\*(C`\e%options\*(C'\fR\fI\fR
.IX Subsection "%options"
.PP
The last parameter, \f(CW\*(C`\e%options\*(C'\fR, must be a hash reference if present.
.PP
Currently the following keys are supported:
.ie n .IP """binmode_stdin"", ""binmode_stdout"", ""binmode_stderr""" 4
.el .IP "\f(CWbinmode_stdin\fR, \f(CWbinmode_stdout\fR, \f(CWbinmode_stderr\fR" 4
.IX Item "binmode_stdin, binmode_stdout, binmode_stderr"
The value must a "layer" as described in "binmode" in perlfunc.  If specified the
corresponding parameter \f(CW$stdin\fR, \f(CW$stdout\fR or \f(CW$stderr\fR, resp., operates
with the given layer.
.Sp
For backward compatibility, a true value that doesn't start with ":"
(e.g. a number) is interpreted as ":raw". If the value is false
or not specified, the default is ":crlf" on Windows and ":raw" otherwise.
.Sp
Don't expect that values other than the built-in layers ":raw", ":crlf",
and (on newer Perls) ":bytes", ":utf8", ":encoding(...)" will work.
.ie n .IP """append_stdout"", ""append_stderr""" 4
.el .IP "\f(CWappend_stdout\fR, \f(CWappend_stderr\fR" 4
.IX Item "append_stdout, append_stderr"
If their value is true then the corresponding parameter \f(CW$stdout\fR or
\&\f(CW$stderr\fR, resp., will append the child's output to the existing "contents" of
the redirector. This only makes sense if the redirector is a simple scalar (the
corresponding file is opened in append mode), a SCALAR reference (the output is
appended to the previous contents of the string) or an ARRAY reference (the
output is \f(CW\*(C`push\*(C'\fRed onto the previous contents of the array).
.ie n .IP """return_if_system_error""" 4
.el .IP \f(CWreturn_if_system_error\fR 4
.IX Item "return_if_system_error"
If this is true \f(CW\*(C`run3\*(C'\fR does \fBnot\fR throw an exception if \f(CW\*(C`system\*(C'\fR returns \-1
(cf. "system" in perlfunc for possible failure scenarios.), but returns true
instead.  In this case \f(CW$?\fR has the value \-1 and \f(CW$!\fR contains the errno of
the failing \f(CW\*(C`system\*(C'\fR call.
.SH "HOW IT WORKS"
.IX Header "HOW IT WORKS"
.IP (1) 4
.IX Item "(1)"
For each redirector \f(CW$stdin\fR, \f(CW$stdout\fR, and \f(CW$stderr\fR, \f(CWrun3()\fR furnishes
a filehandle:
.RS 4
.IP \(bu 4
if the redirector already specifies a filehandle it just uses that
.IP \(bu 4
if the redirector specifies a filename, \f(CWrun3()\fR opens the file
in the appropriate mode
.IP \(bu 4
in all other cases, \f(CWrun3()\fR opens a temporary file (using
tempfile)
.RE
.RS 4
.RE
.IP (2) 4
.IX Item "(2)"
If \f(CWrun3()\fR opened a temporary file for \f(CW$stdin\fR in step (1),
it writes the data using the specified method (either
from a string, an array or returned by a function) to the temporary file and rewinds it.
.IP (3) 4
.IX Item "(3)"
\&\f(CWrun3()\fR saves the parent's \f(CW\*(C`STDIN\*(C'\fR, \f(CW\*(C`STDOUT\*(C'\fR and \f(CW\*(C`STDERR\*(C'\fR by duplicating
them to new filehandles. It duplicates the filehandles from step (1)
to \f(CW\*(C`STDIN\*(C'\fR, \f(CW\*(C`STDOUT\*(C'\fR and \f(CW\*(C`STDERR\*(C'\fR, resp.
.IP (4) 4
.IX Item "(4)"
\&\f(CWrun3()\fR runs the child by invoking system with \f(CW$cmd\fR as
specified above.
.IP (5) 4
.IX Item "(5)"
\&\f(CWrun3()\fR restores the parent's \f(CW\*(C`STDIN\*(C'\fR, \f(CW\*(C`STDOUT\*(C'\fR and \f(CW\*(C`STDERR\*(C'\fR saved in step (3).
.IP (6) 4
.IX Item "(6)"
If \f(CWrun3()\fR opened a temporary file for \f(CW$stdout\fR or \f(CW$stderr\fR in step (1),
it rewinds it and reads back its contents using the specified method (either to
a string, an array or by calling a function).
.IP (7) 4
.IX Item "(7)"
\&\f(CWrun3()\fR closes all filehandles that it opened explicitly in step (1).
.PP
Note that when using temporary files, \f(CWrun3()\fR tries to amortize the overhead
by reusing them (i.e. it keeps them open and rewinds and truncates them
before the next operation).
.SH LIMITATIONS
.IX Header "LIMITATIONS"
Often uses intermediate files (determined by File::Temp, and thus by the
File::Spec defaults and the TMPDIR env. variable) for speed, portability and
simplicity.
.PP
Use extreme caution when using \f(CW\*(C`run3\*(C'\fR in a threaded environment if concurrent
calls of \f(CW\*(C`run3\*(C'\fR are possible. Most likely, I/O from different invocations will
get mixed up. The reason is that in most thread implementations all threads in
a process share the same STDIN/STDOUT/STDERR.  Known failures are Perl ithreads
on Linux and Win32. Note that \f(CW\*(C`fork\*(C'\fR on Win32 is emulated via Win32 threads
and hence I/O mix up is possible between forked children here (\f(CW\*(C`run3\*(C'\fR is "fork
safe" on Unix, though).
.SH DEBUGGING
.IX Header "DEBUGGING"
To enable debugging use the IPCRUN3DEBUG environment variable to
a non-zero integer value:
.PP
.Vb 1
\&  $ IPCRUN3DEBUG=1 myapp
.Ve
.SH PROFILING
.IX Header "PROFILING"
To enable profiling, set IPCRUN3PROFILE to a number to enable emitting profile
information to STDERR (1 to get timestamps, 2 to get a summary report at the
END of the program, 3 to get mini reports after each run) or to a filename to
emit raw data to a file for later analysis.
.SH COMPARISON
.IX Header "COMPARISON"
Here's how it stacks up to existing APIs:
.ie n .SS "compared to system(), ""qx\*(Aq\*(Aq"", ""open ""...|"""", ""open ""|..."""""
.el .SS "compared to \f(CWsystem()\fP, \f(CWqx\*(Aq\*(Aq\fP, \f(CWopen ""...|""\fP, \f(CWopen ""|...""\fP"
.IX Subsection "compared to system(), qx, open ""...|"", open ""|..."""
.IP \(bu 4
better: redirects more than one file descriptor
.IP \(bu 4
better: returns TRUE on success, FALSE on failure
.IP \(bu 4
better: throws an error if problems occur in the parent process (or the
pre-exec child)
.IP \(bu 4
better: allows a very perlish interface to Perl data structures and subroutines
.IP \(bu 4
better: allows 1 word invocations to avoid the shell easily:
.Sp
.Vb 1
\& run3 ["foo"];  # does not invoke shell
.Ve
.IP \(bu 4
worse: does not return the exit code, leaves it in $?
.ie n .SS "compared to open2(), open3()"
.el .SS "compared to \f(CWopen2()\fP, \f(CWopen3()\fP"
.IX Subsection "compared to open2(), open3()"
.IP \(bu 4
better: no lengthy, error prone polling/select loop needed
.IP \(bu 4
better: hides OS dependencies
.IP \(bu 4
better: allows SCALAR, ARRAY, and CODE references to source and sink I/O
.IP \(bu 4
better: I/O parameter order is like \f(CWopen3()\fR  (not like \f(CWopen2()\fR).
.IP \(bu 4
worse: does not allow interaction with the subprocess
.SS "compared to \fBIPC::Run::run()\fP"
.IX Subsection "compared to IPC::Run::run()"
.IP \(bu 4
better: smaller, lower overhead, simpler, more portable
.IP \(bu 4
better: no \fBselect()\fR loop portability issues
.IP \(bu 4
better: does not fall prey to Perl closure leaks
.IP \(bu 4
worse: does not allow interaction with the subprocess (which \fBIPC::Run::run()\fR
allows by redirecting subroutines)
.IP \(bu 4
worse: lacks many features of \f(CWIPC::Run::run()\fR (filters, pipes, redirects,
pty support)
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright 2003, R. Barrie Slaymaker, Jr., All Rights Reserved
.SH LICENSE
.IX Header "LICENSE"
You may use this module under the terms of the BSD, Artistic, or GPL licenses,
any version.
.SH AUTHOR
.IX Header "AUTHOR"
Barrie Slaymaker <\f(CW\*(C`barries@slaysys.com\*(C'\fR>
.PP
Ricardo SIGNES <\f(CW\*(C`rjbs@cpan.org\*(C'\fR> performed routine maintenance since
2010, thanks to help from the following ticket and/or patch submitters: Jody
Belka, Roderich Schupp, David Morel, Jeff Lavallee, and anonymous others.