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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 = 1.02; |
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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 | $pid = open3(\*CHLD_IN, \*CHLD_OUT, \*CHLD_ERR, |
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23 | 'some cmd and args', 'optarg', ...); |
24 | |
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25 | my($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 |
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32 | connects CHLD_OUT for reading from the child, CHLD_IN for writing to |
33 | the child, and CHLD_ERR for errors. If CHLD_ERR is false, or the |
34 | same file descriptor as CHLD_OUT, then STDOUT and STDERR of the child |
35 | are on the same filehandle. The CHLD_IN will have autoflush turned |
36 | on. |
37 | |
38 | If CHLD_IN begins with C<< <& >>, then CHLD_IN will be closed in the |
39 | parent, and the child will read from it directly. If CHLD_OUT or |
40 | CHLD_ERR begins with C<< >& >>, then the child will send output |
41 | directly to that filehandle. In both cases, there will be a dup(2) |
42 | instead of a pipe(2) made. |
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43 | |
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44 | If either reader or writer is the null string, this will be replaced |
45 | by an autogenerated filehandle. If so, you must pass a valid lvalue |
46 | in the parameter slot so it can be overwritten in the caller, or |
47 | an exception will be raised. |
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48 | |
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49 | The filehandles may also be integers, in which case they are understood |
50 | as file descriptors. |
51 | |
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52 | open3() returns the process ID of the child process. It doesn't return on |
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53 | failure: it just raises an exception matching C</^open3:/>. However, |
54 | C<exec> failures in the child are not detected. You'll have to |
55 | trap SIGPIPE yourself. |
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56 | |
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57 | Note if you specify C<-> as the command, in an analogous fashion to |
58 | C<open(FOO, "-|")> the child process will just be the forked Perl |
59 | process rather than an external command. This feature isn't yet |
60 | supported on Win32 platforms. |
61 | |
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62 | open3() does not wait for and reap the child process after it exits. |
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63 | Except for short programs where it's acceptable to let the operating system |
64 | take care of this, you need to do this yourself. This is normally as |
65 | simple as calling C<waitpid $pid, 0> when you're done with the process. |
66 | Failing to do this can result in an accumulation of defunct or "zombie" |
67 | processes. See L<perlfunc/waitpid> for more information. |
68 | |
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69 | If you try to read from the child's stdout writer and their stderr |
70 | writer, you'll have problems with blocking, which means you'll want |
71 | to use select() or the IO::Select, which means you'd best use |
72 | sysread() instead of readline() for normal stuff. |
73 | |
74 | This is very dangerous, as you may block forever. It assumes it's |
75 | going to talk to something like B<bc>, both writing to it and reading |
76 | from it. This is presumably safe because you "know" that commands |
77 | like B<bc> will read a line at a time and output a line at a time. |
78 | Programs like B<sort> that read their entire input stream first, |
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79 | however, are quite apt to cause deadlock. |
80 | |
81 | The big problem with this approach is that if you don't have control |
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82 | over source code being run in the child process, you can't control |
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83 | what it does with pipe buffering. Thus you can't just open a pipe to |
84 | C<cat -v> and continually read and write a line from it. |
85 | |
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86 | =head1 WARNING |
87 | |
88 | The order of arguments differs from that of open2(). |
89 | |
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90 | =cut |
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91 | |
92 | # &open3: Marc Horowitz <marc@mit.edu> |
93 | # derived mostly from &open2 by tom christiansen, <tchrist@convex.com> |
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94 | # fixed for 5.001 by Ulrich Kunitz <kunitz@mai-koeln.com> |
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95 | # ported to Win32 by Ron Schmidt, Merrill Lynch almost ended my career |
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96 | # fixed for autovivving FHs, tchrist again |
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97 | # allow fd numbers to be used, by Frank Tobin |
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98 | # allow '-' as command (c.f. open "-|"), by Adam Spiers <perl@adamspiers.org> |
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99 | # |
100 | # $Id: open3.pl,v 1.1 1993/11/23 06:26:15 marc Exp $ |
101 | # |
102 | # usage: $pid = open3('wtr', 'rdr', 'err' 'some cmd and args', 'optarg', ...); |
103 | # |
104 | # spawn the given $cmd and connect rdr for |
105 | # reading, wtr for writing, and err for errors. |
106 | # if err is '', or the same as rdr, then stdout and |
107 | # stderr of the child are on the same fh. returns pid |
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108 | # of child (or dies on failure). |
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109 | |
110 | |
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111 | # if wtr begins with '<&', then wtr will be closed in the parent, and |
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112 | # the child will read from it directly. if rdr or err begins with |
113 | # '>&', then the child will send output directly to that fd. In both |
114 | # cases, there will be a dup() instead of a pipe() made. |
115 | |
116 | |
117 | # WARNING: this is dangerous, as you may block forever |
118 | # unless you are very careful. |
119 | # |
120 | # $wtr is left unbuffered. |
121 | # |
122 | # abort program if |
123 | # rdr or wtr are null |
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124 | # a system call fails |
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125 | |
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126 | our $Me = 'open3 (bug)'; # you should never see this, it's always localized |
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127 | |
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128 | # Fatal.pm needs to be fixed WRT prototypes. |
129 | |
130 | sub xfork { |
131 | my $pid = fork; |
132 | defined $pid or croak "$Me: fork failed: $!"; |
133 | return $pid; |
134 | } |
135 | |
136 | sub xpipe { |
137 | pipe $_[0], $_[1] or croak "$Me: pipe($_[0], $_[1]) failed: $!"; |
138 | } |
139 | |
140 | # I tried using a * prototype character for the filehandle but it still |
141 | # disallows a bearword while compiling under strict subs. |
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142 | |
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143 | sub xopen { |
144 | open $_[0], $_[1] or croak "$Me: open($_[0], $_[1]) failed: $!"; |
145 | } |
146 | |
147 | sub xclose { |
148 | close $_[0] or croak "$Me: close($_[0]) failed: $!"; |
149 | } |
150 | |
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151 | sub fh_is_fd { |
152 | return $_[0] =~ /\A=?(\d+)\z/; |
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153 | } |
154 | |
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155 | sub xfileno { |
156 | return $1 if $_[0] =~ /\A=?(\d+)\z/; # deal with fh just being an fd |
157 | return fileno $_[0]; |
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158 | } |
159 | |
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160 | my $do_spawn = $^O eq 'os2' || $^O eq 'MSWin32'; |
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161 | |
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162 | sub _open3 { |
163 | local $Me = shift; |
164 | my($package, $dad_wtr, $dad_rdr, $dad_err, @cmd) = @_; |
165 | my($dup_wtr, $dup_rdr, $dup_err, $kidpid); |
166 | |
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167 | # simulate autovivification of filehandles because |
168 | # it's too ugly to use @_ throughout to make perl do it for us |
169 | # tchrist 5-Mar-00 |
170 | |
171 | unless (eval { |
172 | $dad_wtr = $_[1] = gensym unless defined $dad_wtr && length $dad_wtr; |
173 | $dad_rdr = $_[2] = gensym unless defined $dad_rdr && length $dad_rdr; |
174 | 1; }) |
175 | { |
176 | # must strip crud for croak to add back, or looks ugly |
177 | $@ =~ s/(?<=value attempted) at .*//s; |
178 | croak "$Me: $@"; |
179 | } |
180 | |
181 | $dad_err ||= $dad_rdr; |
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182 | |
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183 | $dup_wtr = ($dad_wtr =~ s/^[<>]&//); |
184 | $dup_rdr = ($dad_rdr =~ s/^[<>]&//); |
185 | $dup_err = ($dad_err =~ s/^[<>]&//); |
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186 | |
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187 | # force unqualified filehandles into caller's package |
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188 | $dad_wtr = qualify $dad_wtr, $package unless fh_is_fd($dad_wtr); |
189 | $dad_rdr = qualify $dad_rdr, $package unless fh_is_fd($dad_rdr); |
190 | $dad_err = qualify $dad_err, $package unless fh_is_fd($dad_err); |
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191 | |
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192 | my $kid_rdr = gensym; |
193 | my $kid_wtr = gensym; |
194 | my $kid_err = gensym; |
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195 | |
196 | xpipe $kid_rdr, $dad_wtr if !$dup_wtr; |
197 | xpipe $dad_rdr, $kid_wtr if !$dup_rdr; |
198 | xpipe $dad_err, $kid_err if !$dup_err && $dad_err ne $dad_rdr; |
199 | |
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200 | $kidpid = $do_spawn ? -1 : xfork; |
201 | if ($kidpid == 0) { # Kid |
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202 | # A tie in the parent should not be allowed to cause problems. |
203 | untie *STDIN; |
204 | untie *STDOUT; |
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205 | # If she wants to dup the kid's stderr onto her stdout I need to |
206 | # save a copy of her stdout before I put something else there. |
207 | if ($dad_rdr ne $dad_err && $dup_err |
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208 | && xfileno($dad_err) == fileno(STDOUT)) { |
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209 | my $tmp = gensym; |
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210 | xopen($tmp, ">&$dad_err"); |
211 | $dad_err = $tmp; |
212 | } |
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213 | |
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214 | if ($dup_wtr) { |
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215 | xopen \*STDIN, "<&$dad_wtr" if fileno(STDIN) != xfileno($dad_wtr); |
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216 | } else { |
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217 | xclose $dad_wtr; |
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218 | xopen \*STDIN, "<&=" . fileno $kid_rdr; |
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219 | } |
220 | if ($dup_rdr) { |
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221 | xopen \*STDOUT, ">&$dad_rdr" if fileno(STDOUT) != xfileno($dad_rdr); |
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222 | } else { |
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223 | xclose $dad_rdr; |
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224 | xopen \*STDOUT, ">&=" . fileno $kid_wtr; |
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225 | } |
226 | if ($dad_rdr ne $dad_err) { |
227 | if ($dup_err) { |
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228 | # I have to use a fileno here because in this one case |
229 | # I'm doing a dup but the filehandle might be a reference |
230 | # (from the special case above). |
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231 | xopen \*STDERR, ">&" . xfileno($dad_err) |
232 | if fileno(STDERR) != xfileno($dad_err); |
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233 | } else { |
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234 | xclose $dad_err; |
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235 | xopen \*STDERR, ">&=" . fileno $kid_err; |
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236 | } |
237 | } else { |
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238 | xopen \*STDERR, ">&STDOUT" if fileno(STDERR) != fileno(STDOUT); |
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239 | } |
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240 | if ($cmd[0] eq '-') { |
241 | croak "Arguments don't make sense when the command is '-'" |
242 | if @cmd > 1; |
243 | return 0; |
244 | } |
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245 | local($")=(" "); |
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246 | exec @cmd # XXX: wrong process to croak from |
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247 | or croak "$Me: exec of @cmd failed"; |
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248 | } elsif ($do_spawn) { |
249 | # All the bookkeeping of coincidence between handles is |
250 | # handled in spawn_with_handles. |
251 | |
252 | my @close; |
253 | if ($dup_wtr) { |
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254 | $kid_rdr = \*{$dad_wtr}; |
255 | push @close, $kid_rdr; |
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256 | } else { |
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257 | push @close, \*{$dad_wtr}, $kid_rdr; |
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258 | } |
259 | if ($dup_rdr) { |
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260 | $kid_wtr = \*{$dad_rdr}; |
261 | push @close, $kid_wtr; |
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262 | } else { |
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263 | push @close, \*{$dad_rdr}, $kid_wtr; |
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264 | } |
265 | if ($dad_rdr ne $dad_err) { |
266 | if ($dup_err) { |
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267 | $kid_err = \*{$dad_err}; |
268 | push @close, $kid_err; |
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269 | } else { |
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270 | push @close, \*{$dad_err}, $kid_err; |
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271 | } |
272 | } else { |
273 | $kid_err = $kid_wtr; |
274 | } |
275 | require IO::Pipe; |
276 | $kidpid = eval { |
277 | spawn_with_handles( [ { mode => 'r', |
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278 | open_as => $kid_rdr, |
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279 | handle => \*STDIN }, |
280 | { mode => 'w', |
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281 | open_as => $kid_wtr, |
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282 | handle => \*STDOUT }, |
283 | { mode => 'w', |
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284 | open_as => $kid_err, |
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285 | handle => \*STDERR }, |
286 | ], \@close, @cmd); |
287 | }; |
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288 | die "$Me: $@" if $@; |
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289 | } |
290 | |
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291 | xclose $kid_rdr if !$dup_wtr; |
292 | xclose $kid_wtr if !$dup_rdr; |
293 | xclose $kid_err if !$dup_err && $dad_rdr ne $dad_err; |
294 | # If the write handle is a dup give it away entirely, close my copy |
295 | # of it. |
296 | xclose $dad_wtr if $dup_wtr; |
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297 | |
298 | select((select($dad_wtr), $| = 1)[0]); # unbuffer pipe |
299 | $kidpid; |
300 | } |
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301 | |
302 | sub open3 { |
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303 | if (@_ < 4) { |
304 | local $" = ', '; |
305 | croak "open3(@_): not enough arguments"; |
306 | } |
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307 | return _open3 'open3', scalar caller, @_ |
308 | } |
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309 | |
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310 | sub spawn_with_handles { |
311 | my $fds = shift; # Fields: handle, mode, open_as |
312 | my $close_in_child = shift; |
313 | my ($fd, $pid, @saved_fh, $saved, %saved, @errs); |
314 | require Fcntl; |
315 | |
316 | foreach $fd (@$fds) { |
317 | $fd->{tmp_copy} = IO::Handle->new_from_fd($fd->{handle}, $fd->{mode}); |
318 | $saved{fileno $fd->{handle}} = $fd->{tmp_copy}; |
319 | } |
320 | foreach $fd (@$fds) { |
321 | bless $fd->{handle}, 'IO::Handle' |
322 | unless eval { $fd->{handle}->isa('IO::Handle') } ; |
323 | # If some of handles to redirect-to coincide with handles to |
324 | # redirect, we need to use saved variants: |
325 | $fd->{handle}->fdopen($saved{fileno $fd->{open_as}} || $fd->{open_as}, |
326 | $fd->{mode}); |
327 | } |
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328 | unless ($^O eq 'MSWin32') { |
329 | # Stderr may be redirected below, so we save the err text: |
330 | foreach $fd (@$close_in_child) { |
331 | fcntl($fd, Fcntl::F_SETFD(), 1) or push @errs, "fcntl $fd: $!" |
332 | unless $saved{fileno $fd}; # Do not close what we redirect! |
333 | } |
a24d8dfd |
334 | } |
335 | |
336 | unless (@errs) { |
337 | $pid = eval { system 1, @_ }; # 1 == P_NOWAIT |
338 | push @errs, "IO::Pipe: Can't spawn-NOWAIT: $!" if !$pid || $pid < 0; |
339 | } |
340 | |
341 | foreach $fd (@$fds) { |
342 | $fd->{handle}->fdopen($fd->{tmp_copy}, $fd->{mode}); |
343 | $fd->{tmp_copy}->close or croak "Can't close: $!"; |
344 | } |
345 | croak join "\n", @errs if @errs; |
346 | return $pid; |
347 | } |
348 | |
349 | 1; # so require is happy |