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a0d0e21e |
1 | package IPC::Open2; |
2 | require 5.000; |
3 | require Exporter; |
4 | use Carp; |
5 | |
f06db76b |
6 | =head1 NAME |
7 | |
8 | IPC::Open2, open2 - open a process for both reading and writing |
9 | |
10 | =head1 SYNOPSIS |
11 | |
12 | use IPC::Open2; |
13 | $pid = open2('rdr', 'wtr', 'some cmd and args'); |
14 | # or |
15 | $pid = open2('rdr', 'wtr', 'some', 'cmd', 'and', 'args'); |
16 | |
17 | =head1 DESCRIPTION |
18 | |
19 | The open2() function spawns the given $cmd and connects $rdr for |
20 | reading and $wtr for writing. It's what you think should work |
21 | when you try |
22 | |
23 | open(HANDLE, "|cmd args"); |
24 | |
25 | open2() returns the process ID of the child process. It doesn't return on |
26 | failure: it just raises an exception matching C</^open2:/>. |
27 | |
28 | =head1 WARNING |
29 | |
30 | It will not create these file handles for you. You have to do this yourself. |
31 | So don't pass it empty variables expecting them to get filled in for you. |
32 | |
33 | Additionally, this is very dangerous as you may block forever. |
34 | It assumes it's going to talk to something like B<bc>, both writing to |
35 | it and reading from it. This is presumably safe because you "know" |
36 | that commands like B<bc> will read a line at a time and output a line at |
37 | a time. Programs like B<sort> that read their entire input stream first, |
38 | however, are quite apt to cause deadlock. |
39 | |
40 | The big problem with this approach is that if you don't have control |
41 | over source code being run in the the child process, you can't control what it does |
42 | with pipe buffering. Thus you can't just open a pipe to "cat -v" and continually |
43 | read and write a line from it. |
44 | |
45 | =head1 SEE ALSO |
46 | |
47 | See L<open3> for an alternative that handles STDERR as well. |
48 | |
49 | =cut |
50 | |
a0d0e21e |
51 | @ISA = qw(Exporter); |
52 | @EXPORT = qw(open2); |
53 | |
54 | # &open2: tom christiansen, <tchrist@convex.com> |
55 | # |
56 | # usage: $pid = open2('rdr', 'wtr', 'some cmd and args'); |
57 | # or $pid = open2('rdr', 'wtr', 'some', 'cmd', 'and', 'args'); |
58 | # |
59 | # spawn the given $cmd and connect $rdr for |
60 | # reading and $wtr for writing. return pid |
61 | # of child, or 0 on failure. |
62 | # |
63 | # WARNING: this is dangerous, as you may block forever |
64 | # unless you are very careful. |
65 | # |
66 | # $wtr is left unbuffered. |
67 | # |
68 | # abort program if |
69 | # rdr or wtr are null |
70 | # pipe or fork or exec fails |
71 | |
72 | $fh = 'FHOPEN000'; # package static in case called more than once |
73 | |
74 | sub open2 { |
75 | local($kidpid); |
76 | local($dad_rdr, $dad_wtr, @cmd) = @_; |
77 | |
78 | $dad_rdr ne '' || croak "open2: rdr should not be null"; |
79 | $dad_wtr ne '' || croak "open2: wtr should not be null"; |
80 | |
81 | # force unqualified filehandles into callers' package |
82 | local($package) = caller; |
83 | $dad_rdr =~ s/^[^']+$/$package'$&/; |
84 | $dad_wtr =~ s/^[^']+$/$package'$&/; |
85 | |
86 | local($kid_rdr) = ++$fh; |
87 | local($kid_wtr) = ++$fh; |
88 | |
89 | pipe($dad_rdr, $kid_wtr) || croak "open2: pipe 1 failed: $!"; |
90 | pipe($kid_rdr, $dad_wtr) || croak "open2: pipe 2 failed: $!"; |
91 | |
92 | if (($kidpid = fork) < 0) { |
93 | croak "open2: fork failed: $!"; |
94 | } elsif ($kidpid == 0) { |
95 | close $dad_rdr; close $dad_wtr; |
96 | open(STDIN, "<&$kid_rdr"); |
97 | open(STDOUT, ">&$kid_wtr"); |
98 | warn "execing @cmd\n" if $debug; |
99 | exec @cmd; |
100 | croak "open2: exec of @cmd failed"; |
101 | } |
102 | close $kid_rdr; close $kid_wtr; |
103 | select((select($dad_wtr), $| = 1)[0]); # unbuffer pipe |
104 | $kidpid; |
105 | } |
106 | 1; # so require is happy |
107 | |