diff options
Diffstat (limited to 'contrib/perl5/lib/IPC/Open2.pm')
| -rw-r--r-- | contrib/perl5/lib/IPC/Open2.pm | 75 |
1 files changed, 49 insertions, 26 deletions
diff --git a/contrib/perl5/lib/IPC/Open2.pm b/contrib/perl5/lib/IPC/Open2.pm index 32282d6..a5a3561 100644 --- a/contrib/perl5/lib/IPC/Open2.pm +++ b/contrib/perl5/lib/IPC/Open2.pm @@ -1,7 +1,7 @@ package IPC::Open2; use strict; -use vars qw($VERSION @ISA @EXPORT); +our ($VERSION, @ISA, @EXPORT); require 5.000; require Exporter; @@ -17,47 +17,71 @@ IPC::Open2, open2 - open a process for both reading and writing =head1 SYNOPSIS use IPC::Open2; - $pid = open2(\*RDR, \*WTR, 'some cmd and args'); - # or - $pid = open2(\*RDR, \*WTR, 'some', 'cmd', 'and', 'args'); + + $pid = open2(\*RDRFH, \*WTRFH, 'some cmd and args'); + # or without using the shell + $pid = open2(\*RDRFH, \*WTRFH, 'some', 'cmd', 'and', 'args'); + + # or with handle autovivification + my($rdrfh, $wtrfh); + $pid = open2($rdrfh, $wtrfh, 'some cmd and args'); + # or without using the shell + $pid = open2($rdrfh, $wtrfh, 'some', 'cmd', 'and', 'args'); =head1 DESCRIPTION -The open2() function spawns the given $cmd and connects $rdr for -reading and $wtr for writing. It's what you think should work +The open2() function runs the given $cmd and connects $rdrfh for +reading and $wtrfh for writing. It's what you think should work when you try - open(HANDLE, "|cmd args|"); + $pid = open(HANDLE, "|cmd args|"); The write filehandle will have autoflush turned on. -If $rdr is a string (that is, a bareword filehandle rather than a glob -or a reference) and it begins with ">&", then the child will send output -directly to that file handle. If $wtr is a string that begins with -"<&", then WTR will be closed in the parent, and the child will read +If $rdrfh 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 $wtrfh is a string that begins with +C<< <& >>, then $wtrfh 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. -open2() returns the process ID of the child process. It doesn't return on -failure: it just raises an exception matching C</^open2:/>. - -=head1 WARNING - -It will not create these file handles for you. You have to do this yourself. -So don't pass it empty variables expecting them to get filled in for you. +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. -Additionally, this is very 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. +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 $pid, 0> when you're done with the process. +Failing to do this can result in an accumulation of defunct or "zombie" +processes. See L<perlfunc/waitpid> for more information. + +This whole affair is quite dangerous, as you may block forever. It +assumes it's going to talk to something like B<bc>, both writing +to it and reading from it. This is presumably safe because you +"know" that commands like B<bc> will read a line at a time and +output a line at a time. Programs like B<sort> that read their +entire input stream first, however, are quite apt to cause deadlock. The big problem with this approach is that if you don't have control over source code being run in the child process, you can't control what it does with pipe buffering. Thus you can't just open a pipe to C<cat -v> and continually read and write a line from it. +The IO::Pty and Expect modules from CPAN can help with this, as they +provide a real tty (well, a pseudo-tty, actually), which gets you +back to line buffering in the invoked command again. + +=head1 WARNING + +The order of arguments differs from that of open3(). + =head1 SEE ALSO See L<IPC::Open3> for an alternative that handles STDERR as well. This @@ -86,10 +110,9 @@ function is really just a wrapper around open3(). require IPC::Open3; sub open2 { - my ($read, $write, @cmd) = @_; local $Carp::CarpLevel = $Carp::CarpLevel + 1; return IPC::Open3::_open3('open2', scalar caller, - $write, $read, '>&STDERR', @cmd); + $_[1], $_[0], '>&STDERR', @_[2 .. $#_]); } 1 |
