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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 = 1.0105; |
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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 | The filehandles may also be integers, in which case they are understood |
48 | as file descriptors. |
49 | |
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50 | open3() returns the process ID of the child process. It doesn't return on |
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51 | failure: it just raises an exception matching C</^open3:/>. However, |
52 | C<exec> failures in the child are not detected. You'll have to |
53 | trap SIGPIPE yourself. |
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54 | |
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55 | Note if you specify C<-> as the command, in an analogous fashion to |
56 | C<open(FOO, "-|")> the child process will just be the forked Perl |
57 | process rather than an external command. This feature isn't yet |
58 | supported on Win32 platforms. |
59 | |
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60 | open3() does not wait for and reap the child process after it exits. |
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61 | Except for short programs where it's acceptable to let the operating system |
62 | take care of this, you need to do this yourself. This is normally as |
63 | simple as calling C<waitpid $pid, 0> when you're done with the process. |
64 | Failing to do this can result in an accumulation of defunct or "zombie" |
65 | processes. See L<perlfunc/waitpid> for more information. |
66 | |
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67 | If you try to read from the child's stdout writer and their stderr |
68 | writer, you'll have problems with blocking, which means you'll want |
69 | to use select() or the IO::Select, which means you'd best use |
70 | sysread() instead of readline() for normal stuff. |
71 | |
72 | This is very dangerous, as you may block forever. It assumes it's |
73 | going to talk to something like B<bc>, both writing to it and reading |
74 | from it. This is presumably safe because you "know" that commands |
75 | like B<bc> will read a line at a time and output a line at a time. |
76 | Programs like B<sort> that read their entire input stream first, |
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77 | however, are quite apt to cause deadlock. |
78 | |
79 | The big problem with this approach is that if you don't have control |
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80 | over source code being run in the child process, you can't control |
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81 | what it does with pipe buffering. Thus you can't just open a pipe to |
82 | C<cat -v> and continually read and write a line from it. |
83 | |
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84 | =head1 WARNING |
85 | |
86 | The order of arguments differs from that of open2(). |
87 | |
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88 | =cut |
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89 | |
90 | # &open3: Marc Horowitz <marc@mit.edu> |
91 | # derived mostly from &open2 by tom christiansen, <tchrist@convex.com> |
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92 | # fixed for 5.001 by Ulrich Kunitz <kunitz@mai-koeln.com> |
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93 | # ported to Win32 by Ron Schmidt, Merrill Lynch almost ended my career |
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94 | # fixed for autovivving FHs, tchrist again |
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95 | # allow fd numbers to be used, by Frank Tobin |
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96 | # allow '-' as command (c.f. open "-|"), by Adam Spiers <perl@adamspiers.org> |
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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 |
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106 | # of child (or dies on failure). |
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107 | |
108 | |
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109 | # if wtr begins with '<&', then wtr will be closed in the parent, and |
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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 |
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122 | # a system call fails |
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123 | |
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124 | our $Me = 'open3 (bug)'; # you should never see this, it's always localized |
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125 | |
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126 | # Fatal.pm needs to be fixed WRT prototypes. |
127 | |
128 | sub xfork { |
129 | my $pid = fork; |
130 | defined $pid or croak "$Me: fork failed: $!"; |
131 | return $pid; |
132 | } |
133 | |
134 | sub 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. |
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140 | |
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141 | sub xopen { |
142 | open $_[0], $_[1] or croak "$Me: open($_[0], $_[1]) failed: $!"; |
143 | } |
144 | |
145 | sub xclose { |
146 | close $_[0] or croak "$Me: close($_[0]) failed: $!"; |
147 | } |
148 | |
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149 | sub fh_is_fd { |
150 | return $_[0] =~ /\A=?(\d+)\z/; |
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151 | } |
152 | |
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153 | sub xfileno { |
154 | return $1 if $_[0] =~ /\A=?(\d+)\z/; # deal with fh just being an fd |
155 | return fileno $_[0]; |
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156 | } |
157 | |
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158 | my $do_spawn = $^O eq 'os2' || $^O eq 'MSWin32'; |
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159 | |
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160 | sub _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 | |
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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; |
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180 | |
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181 | $dup_wtr = ($dad_wtr =~ s/^[<>]&//); |
182 | $dup_rdr = ($dad_rdr =~ s/^[<>]&//); |
183 | $dup_err = ($dad_err =~ s/^[<>]&//); |
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184 | |
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185 | # force unqualified filehandles into caller's package |
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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); |
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189 | |
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190 | my $kid_rdr = gensym; |
191 | my $kid_wtr = gensym; |
192 | my $kid_err = gensym; |
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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 | |
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198 | $kidpid = $do_spawn ? -1 : xfork; |
199 | if ($kidpid == 0) { # Kid |
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200 | # If she wants to dup the kid's stderr onto her stdout I need to |
201 | # save a copy of her stdout before I put something else there. |
202 | if ($dad_rdr ne $dad_err && $dup_err |
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203 | && xfileno($dad_err) == fileno(STDOUT)) { |
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204 | my $tmp = gensym; |
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205 | xopen($tmp, ">&$dad_err"); |
206 | $dad_err = $tmp; |
207 | } |
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208 | |
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209 | if ($dup_wtr) { |
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210 | xopen \*STDIN, "<&$dad_wtr" if fileno(STDIN) != xfileno($dad_wtr); |
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211 | } else { |
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212 | xclose $dad_wtr; |
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213 | xopen \*STDIN, "<&=" . fileno $kid_rdr; |
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214 | } |
215 | if ($dup_rdr) { |
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216 | xopen \*STDOUT, ">&$dad_rdr" if fileno(STDOUT) != xfileno($dad_rdr); |
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217 | } else { |
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218 | xclose $dad_rdr; |
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219 | xopen \*STDOUT, ">&=" . fileno $kid_wtr; |
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220 | } |
221 | if ($dad_rdr ne $dad_err) { |
222 | if ($dup_err) { |
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223 | # I have to use a fileno here because in this one case |
224 | # I'm doing a dup but the filehandle might be a reference |
225 | # (from the special case above). |
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226 | xopen \*STDERR, ">&" . xfileno($dad_err) |
227 | if fileno(STDERR) != xfileno($dad_err); |
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228 | } else { |
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229 | xclose $dad_err; |
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230 | xopen \*STDERR, ">&=" . fileno $kid_err; |
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231 | } |
232 | } else { |
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233 | xopen \*STDERR, ">&STDOUT" if fileno(STDERR) != fileno(STDOUT); |
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234 | } |
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235 | if ($cmd[0] eq '-') { |
236 | croak "Arguments don't make sense when the command is '-'" |
237 | if @cmd > 1; |
238 | return 0; |
239 | } |
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240 | local($")=(" "); |
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241 | exec @cmd # XXX: wrong process to croak from |
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242 | or croak "$Me: exec of @cmd failed"; |
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243 | } elsif ($do_spawn) { |
244 | # All the bookkeeping of coincidence between handles is |
245 | # handled in spawn_with_handles. |
246 | |
247 | my @close; |
248 | if ($dup_wtr) { |
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249 | $kid_rdr = \*{$dad_wtr}; |
250 | push @close, $kid_rdr; |
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251 | } else { |
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252 | push @close, \*{$dad_wtr}, $kid_rdr; |
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253 | } |
254 | if ($dup_rdr) { |
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255 | $kid_wtr = \*{$dad_rdr}; |
256 | push @close, $kid_wtr; |
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257 | } else { |
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258 | push @close, \*{$dad_rdr}, $kid_wtr; |
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259 | } |
260 | if ($dad_rdr ne $dad_err) { |
261 | if ($dup_err) { |
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262 | $kid_err = \*{$dad_err}; |
263 | push @close, $kid_err; |
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264 | } else { |
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265 | push @close, \*{$dad_err}, $kid_err; |
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266 | } |
267 | } else { |
268 | $kid_err = $kid_wtr; |
269 | } |
270 | require IO::Pipe; |
271 | $kidpid = eval { |
272 | spawn_with_handles( [ { mode => 'r', |
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273 | open_as => $kid_rdr, |
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274 | handle => \*STDIN }, |
275 | { mode => 'w', |
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276 | open_as => $kid_wtr, |
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277 | handle => \*STDOUT }, |
278 | { mode => 'w', |
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279 | open_as => $kid_err, |
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280 | handle => \*STDERR }, |
281 | ], \@close, @cmd); |
282 | }; |
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283 | die "$Me: $@" if $@; |
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284 | } |
285 | |
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286 | xclose $kid_rdr if !$dup_wtr; |
287 | xclose $kid_wtr if !$dup_rdr; |
288 | xclose $kid_err if !$dup_err && $dad_rdr ne $dad_err; |
289 | # If the write handle is a dup give it away entirely, close my copy |
290 | # of it. |
291 | xclose $dad_wtr if $dup_wtr; |
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292 | |
293 | select((select($dad_wtr), $| = 1)[0]); # unbuffer pipe |
294 | $kidpid; |
295 | } |
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296 | |
297 | sub open3 { |
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298 | if (@_ < 4) { |
299 | local $" = ', '; |
300 | croak "open3(@_): not enough arguments"; |
301 | } |
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302 | return _open3 'open3', scalar caller, @_ |
303 | } |
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304 | |
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305 | sub spawn_with_handles { |
306 | my $fds = shift; # Fields: handle, mode, open_as |
307 | my $close_in_child = shift; |
308 | my ($fd, $pid, @saved_fh, $saved, %saved, @errs); |
309 | require Fcntl; |
310 | |
311 | foreach $fd (@$fds) { |
312 | $fd->{tmp_copy} = IO::Handle->new_from_fd($fd->{handle}, $fd->{mode}); |
313 | $saved{fileno $fd->{handle}} = $fd->{tmp_copy}; |
314 | } |
315 | foreach $fd (@$fds) { |
316 | bless $fd->{handle}, 'IO::Handle' |
317 | unless eval { $fd->{handle}->isa('IO::Handle') } ; |
318 | # If some of handles to redirect-to coincide with handles to |
319 | # redirect, we need to use saved variants: |
320 | $fd->{handle}->fdopen($saved{fileno $fd->{open_as}} || $fd->{open_as}, |
321 | $fd->{mode}); |
322 | } |
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323 | unless ($^O eq 'MSWin32') { |
324 | # Stderr may be redirected below, so we save the err text: |
325 | foreach $fd (@$close_in_child) { |
326 | fcntl($fd, Fcntl::F_SETFD(), 1) or push @errs, "fcntl $fd: $!" |
327 | unless $saved{fileno $fd}; # Do not close what we redirect! |
328 | } |
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329 | } |
330 | |
331 | unless (@errs) { |
332 | $pid = eval { system 1, @_ }; # 1 == P_NOWAIT |
333 | push @errs, "IO::Pipe: Can't spawn-NOWAIT: $!" if !$pid || $pid < 0; |
334 | } |
335 | |
336 | foreach $fd (@$fds) { |
337 | $fd->{handle}->fdopen($fd->{tmp_copy}, $fd->{mode}); |
338 | $fd->{tmp_copy}->close or croak "Can't close: $!"; |
339 | } |
340 | croak join "\n", @errs if @errs; |
341 | return $pid; |
342 | } |
343 | |
344 | 1; # so require is happy |