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1 | package IPC::Open3; |
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2 | |
3 | use strict; |
4 | no strict 'refs'; # because users pass me bareword filehandles |
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5 | our ($VERSION, @ISA, @EXPORT); |
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6 | |
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7 | require Exporter; |
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8 | |
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9 | use Carp; |
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10 | use Symbol qw(gensym qualify); |
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11 | |
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12 | $VERSION = 1.0103; |
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13 | @ISA = qw(Exporter); |
14 | @EXPORT = qw(open3); |
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15 | |
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16 | =head1 NAME |
17 | |
18 | IPC::Open3, open3 - open a process for reading, writing, and error handling |
19 | |
20 | =head1 SYNOPSIS |
21 | |
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22 | $pid = open3(\*WTRFH, \*RDRFH, \*ERRFH, |
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23 | 'some cmd and args', 'optarg', ...); |
24 | |
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25 | my($wtr, $rdr, $err); |
26 | $pid = open3($wtr, $rdr, $err, |
27 | 'some cmd and args', 'optarg', ...); |
28 | |
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29 | =head1 DESCRIPTION |
30 | |
31 | Extremely similar to open2(), open3() spawns the given $cmd and |
32 | connects RDRFH for reading, WTRFH for writing, and ERRFH for errors. If |
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33 | ERRFH is false, or the same file descriptor as RDRFH, then STDOUT and |
34 | STDERR of the child are on the same filehandle. The WTRFH will have |
35 | autoflush turned on. |
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36 | |
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37 | If WTRFH begins with C<< <& >>, then WTRFH will be closed in the parent, and |
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38 | the child will read from it directly. If RDRFH or ERRFH begins with |
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39 | C<< >& >>, then the child will send output directly to that filehandle. |
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40 | In both cases, there will be a dup(2) instead of a pipe(2) made. |
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41 | |
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42 | If either reader or writer is the null string, this will be replaced |
43 | by an autogenerated filehandle. If so, you must pass a valid lvalue |
44 | in the parameter slot so it can be overwritten in the caller, or |
45 | an exception will be raised. |
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46 | |
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47 | open3() returns the process ID of the child process. It doesn't return on |
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48 | failure: it just raises an exception matching C</^open3:/>. However, |
49 | C<exec> failures in the child are not detected. You'll have to |
50 | trap SIGPIPE yourself. |
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51 | |
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52 | open3() does not wait for and reap the child process after it exits. |
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53 | Except for short programs where it's acceptable to let the operating system |
54 | take care of this, you need to do this yourself. This is normally as |
55 | simple as calling C<waitpid $pid, 0> when you're done with the process. |
56 | Failing to do this can result in an accumulation of defunct or "zombie" |
57 | processes. See L<perlfunc/waitpid> for more information. |
58 | |
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59 | If you try to read from the child's stdout writer and their stderr |
60 | writer, you'll have problems with blocking, which means you'll want |
61 | to use select() or the IO::Select, which means you'd best use |
62 | sysread() instead of readline() for normal stuff. |
63 | |
64 | This is very dangerous, as you may block forever. It assumes it's |
65 | going to talk to something like B<bc>, both writing to it and reading |
66 | from it. This is presumably safe because you "know" that commands |
67 | like B<bc> will read a line at a time and output a line at a time. |
68 | Programs like B<sort> that read their entire input stream first, |
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69 | however, are quite apt to cause deadlock. |
70 | |
71 | The big problem with this approach is that if you don't have control |
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72 | over source code being run in the child process, you can't control |
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73 | what it does with pipe buffering. Thus you can't just open a pipe to |
74 | C<cat -v> and continually read and write a line from it. |
75 | |
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76 | =head1 WARNING |
77 | |
78 | The order of arguments differs from that of open2(). |
79 | |
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80 | =cut |
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81 | |
82 | # &open3: Marc Horowitz <marc@mit.edu> |
83 | # derived mostly from &open2 by tom christiansen, <tchrist@convex.com> |
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84 | # fixed for 5.001 by Ulrich Kunitz <kunitz@mai-koeln.com> |
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85 | # ported to Win32 by Ron Schmidt, Merrill Lynch almost ended my career |
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86 | # fixed for autovivving FHs, tchrist again |
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87 | # allow fd numbers to be used, by Frank Tobin |
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88 | # |
89 | # $Id: open3.pl,v 1.1 1993/11/23 06:26:15 marc Exp $ |
90 | # |
91 | # usage: $pid = open3('wtr', 'rdr', 'err' 'some cmd and args', 'optarg', ...); |
92 | # |
93 | # spawn the given $cmd and connect rdr for |
94 | # reading, wtr for writing, and err for errors. |
95 | # if err is '', or the same as rdr, then stdout and |
96 | # stderr of the child are on the same fh. returns pid |
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97 | # of child (or dies on failure). |
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98 | |
99 | |
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100 | # if wtr begins with '<&', then wtr will be closed in the parent, and |
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101 | # the child will read from it directly. if rdr or err begins with |
102 | # '>&', then the child will send output directly to that fd. In both |
103 | # cases, there will be a dup() instead of a pipe() made. |
104 | |
105 | |
106 | # WARNING: this is dangerous, as you may block forever |
107 | # unless you are very careful. |
108 | # |
109 | # $wtr is left unbuffered. |
110 | # |
111 | # abort program if |
112 | # rdr or wtr are null |
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113 | # a system call fails |
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114 | |
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115 | our $Me = 'open3 (bug)'; # you should never see this, it's always localized |
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116 | |
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117 | # Fatal.pm needs to be fixed WRT prototypes. |
118 | |
119 | sub xfork { |
120 | my $pid = fork; |
121 | defined $pid or croak "$Me: fork failed: $!"; |
122 | return $pid; |
123 | } |
124 | |
125 | sub xpipe { |
126 | pipe $_[0], $_[1] or croak "$Me: pipe($_[0], $_[1]) failed: $!"; |
127 | } |
128 | |
129 | # I tried using a * prototype character for the filehandle but it still |
130 | # disallows a bearword while compiling under strict subs. |
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131 | |
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132 | sub xopen { |
133 | open $_[0], $_[1] or croak "$Me: open($_[0], $_[1]) failed: $!"; |
134 | } |
135 | |
136 | sub xclose { |
137 | close $_[0] or croak "$Me: close($_[0]) failed: $!"; |
138 | } |
139 | |
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140 | sub xfileno { |
141 | my ($fh) = @_; |
142 | return $1 if $fh =~ /^=?(\d+)$/; # deal with $fh just being an fd |
143 | return fileno $fh; |
144 | } |
145 | |
146 | sub fh_is_fd { |
147 | return $_[0] =~ /^=?\d+$/; |
148 | } |
149 | |
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150 | my $do_spawn = $^O eq 'os2' || $^O eq 'MSWin32'; |
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151 | |
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152 | sub _open3 { |
153 | local $Me = shift; |
154 | my($package, $dad_wtr, $dad_rdr, $dad_err, @cmd) = @_; |
155 | my($dup_wtr, $dup_rdr, $dup_err, $kidpid); |
156 | |
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157 | # simulate autovivification of filehandles because |
158 | # it's too ugly to use @_ throughout to make perl do it for us |
159 | # tchrist 5-Mar-00 |
160 | |
161 | unless (eval { |
162 | $dad_wtr = $_[1] = gensym unless defined $dad_wtr && length $dad_wtr; |
163 | $dad_rdr = $_[2] = gensym unless defined $dad_rdr && length $dad_rdr; |
164 | 1; }) |
165 | { |
166 | # must strip crud for croak to add back, or looks ugly |
167 | $@ =~ s/(?<=value attempted) at .*//s; |
168 | croak "$Me: $@"; |
169 | } |
170 | |
171 | $dad_err ||= $dad_rdr; |
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172 | |
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173 | $dup_wtr = ($dad_wtr =~ s/^[<>]&//); |
174 | $dup_rdr = ($dad_rdr =~ s/^[<>]&//); |
175 | $dup_err = ($dad_err =~ s/^[<>]&//); |
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176 | |
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177 | # force unqualified filehandles into caller's package |
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178 | $dad_wtr = qualify $dad_wtr, $package unless fh_is_fd($dad_wtr); |
179 | $dad_rdr = qualify $dad_rdr, $package unless fh_is_fd($dad_rdr); |
180 | $dad_err = qualify $dad_err, $package unless fh_is_fd($dad_err); |
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181 | |
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182 | my $kid_rdr = gensym; |
183 | my $kid_wtr = gensym; |
184 | my $kid_err = gensym; |
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185 | |
186 | xpipe $kid_rdr, $dad_wtr if !$dup_wtr; |
187 | xpipe $dad_rdr, $kid_wtr if !$dup_rdr; |
188 | xpipe $dad_err, $kid_err if !$dup_err && $dad_err ne $dad_rdr; |
189 | |
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190 | $kidpid = $do_spawn ? -1 : xfork; |
191 | if ($kidpid == 0) { # Kid |
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192 | # If she wants to dup the kid's stderr onto her stdout I need to |
193 | # save a copy of her stdout before I put something else there. |
194 | if ($dad_rdr ne $dad_err && $dup_err |
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195 | && xfileno($dad_err) == fileno(STDOUT)) { |
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196 | my $tmp = gensym; |
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197 | xopen($tmp, ">&$dad_err"); |
198 | $dad_err = $tmp; |
199 | } |
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200 | |
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201 | if ($dup_wtr) { |
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202 | xopen \*STDIN, "<&$dad_wtr" if fileno(STDIN) != xfileno($dad_wtr); |
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203 | } else { |
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204 | xclose $dad_wtr; |
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205 | xopen \*STDIN, "<&=" . fileno $kid_rdr; |
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206 | } |
207 | if ($dup_rdr) { |
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208 | xopen \*STDOUT, ">&$dad_rdr" if fileno(STDOUT) != xfileno($dad_rdr); |
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209 | } else { |
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210 | xclose $dad_rdr; |
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211 | xopen \*STDOUT, ">&=" . fileno $kid_wtr; |
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212 | } |
213 | if ($dad_rdr ne $dad_err) { |
214 | if ($dup_err) { |
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215 | # I have to use a fileno here because in this one case |
216 | # I'm doing a dup but the filehandle might be a reference |
217 | # (from the special case above). |
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218 | xopen \*STDERR, ">&" . xfileno($dad_err) |
219 | if fileno(STDERR) != xfileno($dad_err); |
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220 | } else { |
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221 | xclose $dad_err; |
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222 | xopen \*STDERR, ">&=" . fileno $kid_err; |
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223 | } |
224 | } else { |
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225 | xopen \*STDERR, ">&STDOUT" if fileno(STDERR) != fileno(STDOUT); |
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226 | } |
227 | local($")=(" "); |
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228 | exec @cmd # XXX: wrong process to croak from |
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229 | or croak "$Me: exec of @cmd failed"; |
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230 | } elsif ($do_spawn) { |
231 | # All the bookkeeping of coincidence between handles is |
232 | # handled in spawn_with_handles. |
233 | |
234 | my @close; |
235 | if ($dup_wtr) { |
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236 | $kid_rdr = \*{$dad_wtr}; |
237 | push @close, $kid_rdr; |
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238 | } else { |
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239 | push @close, \*{$dad_wtr}, $kid_rdr; |
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240 | } |
241 | if ($dup_rdr) { |
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242 | $kid_wtr = \*{$dad_rdr}; |
243 | push @close, $kid_wtr; |
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244 | } else { |
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245 | push @close, \*{$dad_rdr}, $kid_wtr; |
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246 | } |
247 | if ($dad_rdr ne $dad_err) { |
248 | if ($dup_err) { |
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249 | $kid_err = \*{$dad_err}; |
250 | push @close, $kid_err; |
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251 | } else { |
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252 | push @close, \*{$dad_err}, $kid_err; |
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253 | } |
254 | } else { |
255 | $kid_err = $kid_wtr; |
256 | } |
257 | require IO::Pipe; |
258 | $kidpid = eval { |
259 | spawn_with_handles( [ { mode => 'r', |
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260 | open_as => $kid_rdr, |
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261 | handle => \*STDIN }, |
262 | { mode => 'w', |
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263 | open_as => $kid_wtr, |
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264 | handle => \*STDOUT }, |
265 | { mode => 'w', |
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266 | open_as => $kid_err, |
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267 | handle => \*STDERR }, |
268 | ], \@close, @cmd); |
269 | }; |
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270 | die "$Me: $@" if $@; |
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271 | } |
272 | |
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273 | xclose $kid_rdr if !$dup_wtr; |
274 | xclose $kid_wtr if !$dup_rdr; |
275 | xclose $kid_err if !$dup_err && $dad_rdr ne $dad_err; |
276 | # If the write handle is a dup give it away entirely, close my copy |
277 | # of it. |
278 | xclose $dad_wtr if $dup_wtr; |
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279 | |
280 | select((select($dad_wtr), $| = 1)[0]); # unbuffer pipe |
281 | $kidpid; |
282 | } |
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283 | |
284 | sub open3 { |
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285 | if (@_ < 4) { |
286 | local $" = ', '; |
287 | croak "open3(@_): not enough arguments"; |
288 | } |
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289 | return _open3 'open3', scalar caller, @_ |
290 | } |
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291 | |
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292 | sub spawn_with_handles { |
293 | my $fds = shift; # Fields: handle, mode, open_as |
294 | my $close_in_child = shift; |
295 | my ($fd, $pid, @saved_fh, $saved, %saved, @errs); |
296 | require Fcntl; |
297 | |
298 | foreach $fd (@$fds) { |
299 | $fd->{tmp_copy} = IO::Handle->new_from_fd($fd->{handle}, $fd->{mode}); |
300 | $saved{fileno $fd->{handle}} = $fd->{tmp_copy}; |
301 | } |
302 | foreach $fd (@$fds) { |
303 | bless $fd->{handle}, 'IO::Handle' |
304 | unless eval { $fd->{handle}->isa('IO::Handle') } ; |
305 | # If some of handles to redirect-to coincide with handles to |
306 | # redirect, we need to use saved variants: |
307 | $fd->{handle}->fdopen($saved{fileno $fd->{open_as}} || $fd->{open_as}, |
308 | $fd->{mode}); |
309 | } |
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310 | unless ($^O eq 'MSWin32') { |
311 | # Stderr may be redirected below, so we save the err text: |
312 | foreach $fd (@$close_in_child) { |
313 | fcntl($fd, Fcntl::F_SETFD(), 1) or push @errs, "fcntl $fd: $!" |
314 | unless $saved{fileno $fd}; # Do not close what we redirect! |
315 | } |
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316 | } |
317 | |
318 | unless (@errs) { |
319 | $pid = eval { system 1, @_ }; # 1 == P_NOWAIT |
320 | push @errs, "IO::Pipe: Can't spawn-NOWAIT: $!" if !$pid || $pid < 0; |
321 | } |
322 | |
323 | foreach $fd (@$fds) { |
324 | $fd->{handle}->fdopen($fd->{tmp_copy}, $fd->{mode}); |
325 | $fd->{tmp_copy}->close or croak "Can't close: $!"; |
326 | } |
327 | croak join "\n", @errs if @errs; |
328 | return $pid; |
329 | } |
330 | |
331 | 1; # so require is happy |