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Diffstat (limited to 'systems/texlive/tlnet/tlpkg/tlperl/lib/IPC/Open2.pm')
-rw-r--r-- | systems/texlive/tlnet/tlpkg/tlperl/lib/IPC/Open2.pm | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/systems/texlive/tlnet/tlpkg/tlperl/lib/IPC/Open2.pm b/systems/texlive/tlnet/tlpkg/tlperl/lib/IPC/Open2.pm new file mode 100644 index 0000000000..9e27144571 --- /dev/null +++ b/systems/texlive/tlnet/tlpkg/tlperl/lib/IPC/Open2.pm @@ -0,0 +1,120 @@ +package IPC::Open2; + +use strict; +our ($VERSION, @ISA, @EXPORT); + +require 5.000; +require Exporter; + +$VERSION = 1.04; +@ISA = qw(Exporter); +@EXPORT = qw(open2); + +=head1 NAME + +IPC::Open2 - open a process for both reading and writing using open2() + +=head1 SYNOPSIS + + use IPC::Open2; + + $pid = open2(\*CHLD_OUT, \*CHLD_IN, 'some cmd and args'); + # or without using the shell + $pid = open2(\*CHLD_OUT, \*CHLD_IN, 'some', 'cmd', 'and', 'args'); + + # or with handle autovivification + my($chld_out, $chld_in); + $pid = open2($chld_out, $chld_in, 'some cmd and args'); + # or without using the shell + $pid = open2($chld_out, $chld_in, 'some', 'cmd', 'and', 'args'); + + waitpid( $pid, 0 ); + my $child_exit_status = $? >> 8; + +=head1 DESCRIPTION + +The open2() function runs the given $cmd and connects $chld_out for +reading and $chld_in for writing. It's what you think should work +when you try + + $pid = open(HANDLE, "|cmd args|"); + +The write filehandle will have autoflush turned on. + +If $chld_out is a string (that is, a bareword filehandle rather than a glob +or a reference) and it begins with C<< >& >>, then the child will send output +directly to that file handle. If $chld_in is a string that begins with +C<< <& >>, then $chld_in will be closed in the parent, and the child will +read from it directly. In both cases, there will be a dup(2) instead of a +pipe(2) made. + +If either reader or writer is the null string, this will be replaced +by an autogenerated filehandle. If so, you must pass a valid lvalue +in the parameter slot so it can be overwritten in the caller, or +an exception will be raised. + +open2() returns the process ID of the child process. It doesn't return on +failure: it just raises an exception matching C</^open2:/>. However, +C<exec> failures in the child are not detected. You'll have to +trap SIGPIPE yourself. + +open2() does not wait for and reap the child process after it exits. +Except for short programs where it's acceptable to let the operating system +take care of this, you need to do this yourself. This is normally as +simple as calling C<waitpid $pid, 0> when you're done with the process. +Failing to do this can result in an accumulation of defunct or "zombie" +processes. See L<perlfunc/waitpid> for more information. + +This whole affair is quite dangerous, as you may block forever. It +assumes it's going to talk to something like B<bc>, both writing +to it and reading from it. This is presumably safe because you +"know" that commands like B<bc> will read a line at a time and +output a line at a time. Programs like B<sort> that read their +entire input stream first, however, are quite apt to cause deadlock. + +The big problem with this approach is that if you don't have control +over source code being run in the child process, you can't control +what it does with pipe buffering. Thus you can't just open a pipe to +C<cat -v> and continually read and write a line from it. + +The IO::Pty and Expect modules from CPAN can help with this, as they +provide a real tty (well, a pseudo-tty, actually), which gets you +back to line buffering in the invoked command again. + +=head1 WARNING + +The order of arguments differs from that of open3(). + +=head1 SEE ALSO + +See L<IPC::Open3> for an alternative that handles STDERR as well. This +function is really just a wrapper around open3(). + +=cut + +# &open2: tom christiansen, <tchrist@convex.com> +# +# usage: $pid = open2('rdr', 'wtr', 'some cmd and args'); +# or $pid = open2('rdr', 'wtr', 'some', 'cmd', 'and', 'args'); +# +# spawn the given $cmd and connect $rdr for +# reading and $wtr for writing. return pid +# of child, or 0 on failure. +# +# WARNING: this is dangerous, as you may block forever +# unless you are very careful. +# +# $wtr is left unbuffered. +# +# abort program if +# rdr or wtr are null +# a system call fails + +require IPC::Open3; + +sub open2 { + local $Carp::CarpLevel = $Carp::CarpLevel + 1; + return IPC::Open3::_open3('open2', $_[1], $_[0], '>&STDERR', @_[2 .. $#_]); +} + +1 |