1package IPC::Open3; 2 3use strict; 4no strict 'refs'; # because users pass me bareword filehandles 5our ($VERSION, @ISA, @EXPORT); 6 7require Exporter; 8 9use Carp; 10use Symbol qw(gensym qualify); 11 12$VERSION = 1.0106; 13@ISA = qw(Exporter); 14@EXPORT = qw(open3); 15 16=head1 NAME 17 18IPC::Open3, open3 - open a process for reading, writing, and error handling 19 20=head1 SYNOPSIS 21 22 $pid = open3(\*WTRFH, \*RDRFH, \*ERRFH, 23 'some cmd and args', 'optarg', ...); 24 25 my($wtr, $rdr, $err); 26 $pid = open3($wtr, $rdr, $err, 27 'some cmd and args', 'optarg', ...); 28 29=head1 DESCRIPTION 30 31Extremely similar to open2(), open3() spawns the given $cmd and 32connects RDRFH for reading, WTRFH for writing, and ERRFH for errors. If 33ERRFH is false, or the same file descriptor as RDRFH, then STDOUT and 34STDERR of the child are on the same filehandle. The WTRFH will have 35autoflush turned on. 36 37If WTRFH begins with C<< <& >>, then WTRFH will be closed in the parent, and 38the child will read from it directly. If RDRFH or ERRFH begins with 39C<< >& >>, then the child will send output directly to that filehandle. 40In both cases, there will be a dup(2) instead of a pipe(2) made. 41 42If either reader or writer is the null string, this will be replaced 43by an autogenerated filehandle. If so, you must pass a valid lvalue 44in the parameter slot so it can be overwritten in the caller, or 45an exception will be raised. 46 47The filehandles may also be integers, in which case they are understood 48as file descriptors. 49 50open3() returns the process ID of the child process. It doesn't return on 51failure: it just raises an exception matching C</^open3:/>. However, 52C<exec> failures in the child are not detected. You'll have to 53trap SIGPIPE yourself. 54 55Note if you specify C<-> as the command, in an analogous fashion to 56C<open(FOO, "-|")> the child process will just be the forked Perl 57process rather than an external command. This feature isn't yet 58supported on Win32 platforms. 59 60open3() does not wait for and reap the child process after it exits. 61Except for short programs where it's acceptable to let the operating system 62take care of this, you need to do this yourself. This is normally as 63simple as calling C<waitpid $pid, 0> when you're done with the process. 64Failing to do this can result in an accumulation of defunct or "zombie" 65processes. See L<perlfunc/waitpid> for more information. 66 67If you try to read from the child's stdout writer and their stderr 68writer, you'll have problems with blocking, which means you'll want 69to use select() or the IO::Select, which means you'd best use 70sysread() instead of readline() for normal stuff. 71 72This is very dangerous, as you may block forever. It assumes it's 73going to talk to something like B<bc>, both writing to it and reading 74from it. This is presumably safe because you "know" that commands 75like B<bc> will read a line at a time and output a line at a time. 76Programs like B<sort> that read their entire input stream first, 77however, are quite apt to cause deadlock. 78 79The big problem with this approach is that if you don't have control 80over source code being run in the child process, you can't control 81what it does with pipe buffering. Thus you can't just open a pipe to 82C<cat -v> and continually read and write a line from it. 83 84=head1 WARNING 85 86The order of arguments differs from that of open2(). 87 88=cut 89 90# &open3: Marc Horowitz <marc@mit.edu> 91# derived mostly from &open2 by tom christiansen, <tchrist@convex.com> 92# fixed for 5.001 by Ulrich Kunitz <kunitz@mai-koeln.com> 93# ported to Win32 by Ron Schmidt, Merrill Lynch almost ended my career 94# fixed for autovivving FHs, tchrist again 95# allow fd numbers to be used, by Frank Tobin 96# allow '-' as command (c.f. open "-|"), by Adam Spiers <perl@adamspiers.org> 97# 98# $Id: open3.pl,v 1.1 1993/11/23 06:26:15 marc Exp $ 99# 100# usage: $pid = open3('wtr', 'rdr', 'err' 'some cmd and args', 'optarg', ...); 101# 102# spawn the given $cmd and connect rdr for 103# reading, wtr for writing, and err for errors. 104# if err is '', or the same as rdr, then stdout and 105# stderr of the child are on the same fh. returns pid 106# of child (or dies on failure). 107 108 109# if wtr begins with '<&', then wtr will be closed in the parent, and 110# the child will read from it directly. if rdr or err begins with 111# '>&', then the child will send output directly to that fd. In both 112# cases, there will be a dup() instead of a pipe() made. 113 114 115# WARNING: this is dangerous, as you may block forever 116# unless you are very careful. 117# 118# $wtr is left unbuffered. 119# 120# abort program if 121# rdr or wtr are null 122# a system call fails 123 124our $Me = 'open3 (bug)'; # you should never see this, it's always localized 125 126# Fatal.pm needs to be fixed WRT prototypes. 127 128sub xfork { 129 my $pid = fork; 130 defined $pid or croak "$Me: fork failed: $!"; 131 return $pid; 132} 133 134sub xpipe { 135 pipe $_[0], $_[1] or croak "$Me: pipe($_[0], $_[1]) failed: $!"; 136} 137 138# I tried using a * prototype character for the filehandle but it still 139# disallows a bearword while compiling under strict subs. 140 141sub xopen { 142 open $_[0], $_[1] or croak "$Me: open($_[0], $_[1]) failed: $!"; 143} 144 145sub xclose { 146 close $_[0] or croak "$Me: close($_[0]) failed: $!"; 147} 148 149sub fh_is_fd { 150 return $_[0] =~ /\A=?(\d+)\z/; 151} 152 153sub xfileno { 154 return $1 if $_[0] =~ /\A=?(\d+)\z/; # deal with fh just being an fd 155 return fileno $_[0]; 156} 157 158my $do_spawn = $^O eq 'os2' || $^O eq 'MSWin32'; 159 160sub _open3 { 161 local $Me = shift; 162 my($package, $dad_wtr, $dad_rdr, $dad_err, @cmd) = @_; 163 my($dup_wtr, $dup_rdr, $dup_err, $kidpid); 164 165 # simulate autovivification of filehandles because 166 # it's too ugly to use @_ throughout to make perl do it for us 167 # tchrist 5-Mar-00 168 169 unless (eval { 170 $dad_wtr = $_[1] = gensym unless defined $dad_wtr && length $dad_wtr; 171 $dad_rdr = $_[2] = gensym unless defined $dad_rdr && length $dad_rdr; 172 1; }) 173 { 174 # must strip crud for croak to add back, or looks ugly 175 $@ =~ s/(?<=value attempted) at .*//s; 176 croak "$Me: $@"; 177 } 178 179 $dad_err ||= $dad_rdr; 180 181 $dup_wtr = ($dad_wtr =~ s/^[<>]&//); 182 $dup_rdr = ($dad_rdr =~ s/^[<>]&//); 183 $dup_err = ($dad_err =~ s/^[<>]&//); 184 185 # force unqualified filehandles into caller's package 186 $dad_wtr = qualify $dad_wtr, $package unless fh_is_fd($dad_wtr); 187 $dad_rdr = qualify $dad_rdr, $package unless fh_is_fd($dad_rdr); 188 $dad_err = qualify $dad_err, $package unless fh_is_fd($dad_err); 189 190 my $kid_rdr = gensym; 191 my $kid_wtr = gensym; 192 my $kid_err = gensym; 193 194 xpipe $kid_rdr, $dad_wtr if !$dup_wtr; 195 xpipe $dad_rdr, $kid_wtr if !$dup_rdr; 196 xpipe $dad_err, $kid_err if !$dup_err && $dad_err ne $dad_rdr; 197 198 $kidpid = $do_spawn ? -1 : xfork; 199 if ($kidpid == 0) { # Kid 200 # A tie in the parent should not be allowed to cause problems. 201 untie *STDIN; 202 untie *STDOUT; 203 # If she wants to dup the kid's stderr onto her stdout I need to 204 # save a copy of her stdout before I put something else there. 205 if ($dad_rdr ne $dad_err && $dup_err 206 && xfileno($dad_err) == fileno(STDOUT)) { 207 my $tmp = gensym; 208 xopen($tmp, ">&$dad_err"); 209 $dad_err = $tmp; 210 } 211 212 if ($dup_wtr) { 213 xopen \*STDIN, "<&$dad_wtr" if fileno(STDIN) != xfileno($dad_wtr); 214 } else { 215 xclose $dad_wtr; 216 xopen \*STDIN, "<&=" . fileno $kid_rdr; 217 } 218 if ($dup_rdr) { 219 xopen \*STDOUT, ">&$dad_rdr" if fileno(STDOUT) != xfileno($dad_rdr); 220 } else { 221 xclose $dad_rdr; 222 xopen \*STDOUT, ">&=" . fileno $kid_wtr; 223 } 224 if ($dad_rdr ne $dad_err) { 225 if ($dup_err) { 226 # I have to use a fileno here because in this one case 227 # I'm doing a dup but the filehandle might be a reference 228 # (from the special case above). 229 xopen \*STDERR, ">&" . xfileno($dad_err) 230 if fileno(STDERR) != xfileno($dad_err); 231 } else { 232 xclose $dad_err; 233 xopen \*STDERR, ">&=" . fileno $kid_err; 234 } 235 } else { 236 xopen \*STDERR, ">&STDOUT" if fileno(STDERR) != fileno(STDOUT); 237 } 238 if ($cmd[0] eq '-') { 239 croak "Arguments don't make sense when the command is '-'" 240 if @cmd > 1; 241 return 0; 242 } 243 local($")=(" "); 244 exec @cmd # XXX: wrong process to croak from 245 or croak "$Me: exec of @cmd failed"; 246 } elsif ($do_spawn) { 247 # All the bookkeeping of coincidence between handles is 248 # handled in spawn_with_handles. 249 250 my @close; 251 if ($dup_wtr) { 252 $kid_rdr = \*{$dad_wtr}; 253 push @close, $kid_rdr; 254 } else { 255 push @close, \*{$dad_wtr}, $kid_rdr; 256 } 257 if ($dup_rdr) { 258 $kid_wtr = \*{$dad_rdr}; 259 push @close, $kid_wtr; 260 } else { 261 push @close, \*{$dad_rdr}, $kid_wtr; 262 } 263 if ($dad_rdr ne $dad_err) { 264 if ($dup_err) { 265 $kid_err = \*{$dad_err}; 266 push @close, $kid_err; 267 } else { 268 push @close, \*{$dad_err}, $kid_err; 269 } 270 } else { 271 $kid_err = $kid_wtr; 272 } 273 require IO::Pipe; 274 $kidpid = eval { 275 spawn_with_handles( [ { mode => 'r', 276 open_as => $kid_rdr, 277 handle => \*STDIN }, 278 { mode => 'w', 279 open_as => $kid_wtr, 280 handle => \*STDOUT }, 281 { mode => 'w', 282 open_as => $kid_err, 283 handle => \*STDERR }, 284 ], \@close, @cmd); 285 }; 286 die "$Me: $@" if $@; 287 } 288 289 xclose $kid_rdr if !$dup_wtr; 290 xclose $kid_wtr if !$dup_rdr; 291 xclose $kid_err if !$dup_err && $dad_rdr ne $dad_err; 292 # If the write handle is a dup give it away entirely, close my copy 293 # of it. 294 xclose $dad_wtr if $dup_wtr; 295 296 select((select($dad_wtr), $| = 1)[0]); # unbuffer pipe 297 $kidpid; 298} 299 300sub open3 { 301 if (@_ < 4) { 302 local $" = ', '; 303 croak "open3(@_): not enough arguments"; 304 } 305 return _open3 'open3', scalar caller, @_ 306} 307 308sub spawn_with_handles { 309 my $fds = shift; # Fields: handle, mode, open_as 310 my $close_in_child = shift; 311 my ($fd, $pid, @saved_fh, $saved, %saved, @errs); 312 require Fcntl; 313 314 foreach $fd (@$fds) { 315 $fd->{tmp_copy} = IO::Handle->new_from_fd($fd->{handle}, $fd->{mode}); 316 $saved{fileno $fd->{handle}} = $fd->{tmp_copy}; 317 } 318 foreach $fd (@$fds) { 319 bless $fd->{handle}, 'IO::Handle' 320 unless eval { $fd->{handle}->isa('IO::Handle') } ; 321 # If some of handles to redirect-to coincide with handles to 322 # redirect, we need to use saved variants: 323 $fd->{handle}->fdopen($saved{fileno $fd->{open_as}} || $fd->{open_as}, 324 $fd->{mode}); 325 } 326 unless ($^O eq 'MSWin32') { 327 # Stderr may be redirected below, so we save the err text: 328 foreach $fd (@$close_in_child) { 329 fcntl($fd, Fcntl::F_SETFD(), 1) or push @errs, "fcntl $fd: $!" 330 unless $saved{fileno $fd}; # Do not close what we redirect! 331 } 332 } 333 334 unless (@errs) { 335 $pid = eval { system 1, @_ }; # 1 == P_NOWAIT 336 push @errs, "IO::Pipe: Can't spawn-NOWAIT: $!" if !$pid || $pid < 0; 337 } 338 339 foreach $fd (@$fds) { 340 $fd->{handle}->fdopen($fd->{tmp_copy}, $fd->{mode}); 341 $fd->{tmp_copy}->close or croak "Can't close: $!"; 342 } 343 croak join "\n", @errs if @errs; 344 return $pid; 345} 346 3471; # so require is happy 348