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How to execute
external programs
in Perl
Shoichi Kaji
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About Me
• Shoichi Kaji
• One of the maintainers of
Minilla, Perl::Build,
Text::Xslate, Mouse,
Test::PAUSE::Permissions
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͡Ίʹ
• PerlbetterγΣϧͱݺΕΔ
• ΑͬͯPerlͰ֎෦ϓϩάϥϜΛ࣮ߦ͢Δػձଟ͍
• ҰํͰ֎෦ϓϩάϥϜ࣮ߦߟྀ͖͢͜ͱ͕
ͨ͘͞Μ͋Δ
• ࢥ͍ͷ··ʹ֎෦ϓϩάϥϜΛ࣮ߦͰ͖ΔΑ͏ʹ
ͳΓ͍ͨ
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Perlͷ֎෦ϓϩάϥϜ࣮ߦؔ࿈ͷ
τϐοΫε
• shellΛհ͔͢Βͣ ←ࠓ͜͜ͱ
• redirect, pipe ←͜͜Λѻ͏
• γάφϧ
• Windows
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࣍
• shellΛհ͔͢Βͣ
• ֎෦ϓϩάϥϜΛ࣮ߦ͢ΔPerlͷؔ
• fork & exec
• redirect
• pipe
• ·ͱΊ
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shellΛհ͔͢Βͣ
• system "find $dir -type f -delete >/dev/null
2>&1";
• Ͳ͕͜ʁ
• systemexecΛ1ҾͰ࣮ߦ͢ΔͱshellΛհ͠
࣮ͯߦ͢ΔՄೳੑ͕͋Δɻ
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shellΛհ͔͢Βͣ
• ͍ΘΏΔshell injectionͷ͓ͦΕ͕͋Δɻ$dirʹ
มͳจࣈ͍ΕΒΕͨΒʁ
• ֎෦ϓϩάϥϜʹγάφϧૹͬͨͭΓ͕shell
ʹૹΔ͜ͱʹͳΔ
• ۭനจࣈΛؚΉϑΝΠϧͰదʹΫΦʔτ͠ͳ
͚Ε͍͚ͳ͍
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shellΛհ͔͢Βͣ
• shellΛىಈ͠ͳ͍ͷ͕Ұ൪
• ͍ΘΏΔinderectه๏Λ͑Ͱ͖Δ
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#!/usr/bin/env perl
use strict;
use warnings;
system {"perl"} "perl", "-E", 'say "hello!"';
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֎෦ϓϩάϥϜΛ࣮ߦ͢Δ
Perlͷؔ
• ҎԼͷ4ͭ
• system
• ` ` (όοΫΫΦʔτ, qx)
• fork & exec ← ࠓ͜Εʹ
• open (͜Ε͕Ұ൪PerlͬΆ͍!)
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fork & exec
• ࠓfork & execͰ֎෦ϓϩάϥϜΛىಈͯ͠
ΈΔ
• forkࣗͷΛ࡞ΔγεςϜίʔϧ
• execࣗΛมԽͤ͞ΔγεςϜίʔϧ
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#!/usr/bin/env perl
use strict;
use warnings;
my $pid = fork // die;
if ($pid == 0) {
exec {"ls"} "ls", "-al";
exit 127;
}
wait;
my $status = $?;
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redirect
• system "gzip —stdout out.txt";
• ίϚϯυͷग़ྗΛout.txt.gzʹ͚͍ͨɻ
• system "gzip —stdout out.txt > out.txt.gz";
Γͨ͘ͳ͍ɻ
• open STDOUT, ">", "out.txt.gz" ͰͰ͖Δ
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#!/usr/bin/env perl
use strict;
use warnings;
my $pid = fork // die;
if ($pid == 0) {
open STDOUT, ">", "out.txt.gz";
exec {"gzip"} "gzip", "--stdout", "out.txt";
exit 127;
}
wait;
my $status = $?;
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pipe
• ͘ଓ͘ϓϩάϥϜͷग़ྗʹ࣌ࠁΛ͚͍ͭͨɻ
• pipeͰ֎෦ϓϩάϥϜͷग़ྗΛϦΞϧλΠϜʹ
ड͚औΕ͍͍
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#!/usr/bin/env perl
use strict;
use warnings;
use POSIX 'strftime';
pipe my $stdout_read, my $stdout_write;
my $pid = fork // die;
if ($pid == 0) {
close $stdout_read;
open STDOUT, ">&=", $stdout_write;
exec {"perl"} "perl", "-le",
'$|++; for (1..10) { print $_; sleep 1 }';
}
close $stdout_write;
while (<$stdout_read>) {
print strftime("%FT%T", localtime) . " $_";
}
wait;
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stderrऔΓ͍ͨ
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#!/usr/bin/env perl
use strict;
use warnings;
use POSIX 'strftime';
pipe my $stdout_read, my $stdout_write;
my $pid = fork // die;
if ($pid == 0) {
close $stdout_read;
open STDOUT, ">&=", $stdout_write;
open STDERR, ">&=", \*STDOUT;
exec {"perl"} "perl", "-le",
'$|++; for (1..10) { print $_; warn $_; sleep 1 }';
}
close $stdout_write;
while (<$stdout_read>) {
print strftime("%FT%T", localtime) . " $_";
}
wait;
ϦμΠϨΫτ!
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stdout/errผʑʹऔΓ
͍ͨ
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#!/usr/bin/env perl
use strict;
use warnings;
use POSIX 'strftime';
use IO::Select;
pipe my $stdout_read, my $stdout_write;
pipe my $stderr_read, my $stderr_write;
my $pid = fork // die;
if ($pid == 0) {
close $stdout_read;
close $stderr_read;
open STDOUT, ">&=", $stdout_write;
open STDERR, ">&=", $stderr_write;
exec {"perl"} "perl", "-le",
'$|++; for (1..10) { print $_; warn $_; sleep 1 }';
}
close $stdout_write;
close $stderr_write;
my $select = IO::Select->new($stdout_read, $stderr_read);
while ($select->count) {
for my $fh ($select->can_read) {
my $len = sysread $fh, my $str, 1024;
if ($len) {
my $type = $fh == $stdout_read ? "out": "err";
print strftime("%FT%T", localtime) . " $type $str";
} else {
$select->remove($fh);
close $fh;
}
}
}
wait;
select!
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·ͱΊ
• ֎෦ϓϩάϥϜ࣮ߦͰindirectه๏Λͬͯ
shellΛհ͞ͳ͍ͷ͕͍͍Γํ
• open STDOUT, ">", "file.txt" ͰSTDOUTΛϑΝ
ΠϧʹϦμΠϨΫτͰ͖Δ
• pipeΛۦͯ͠֎෦ϓϩάϥϜͱ௨৴Ͱ͖Δ
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Further Reading
• CPAN moduleΛಡΉͷ͕͓͢͢Ί
• IPC::Run3, System::Command, Capture::Tiny
• Proclet, Server::Starter