in reply to Can't close pipe to invalid process
I think that this behaviour is caused by the fact that Perl has to launch a shell to process a command given in a string form, and the open doesn't fail because shell does launch successfully (it's the command that fails later):
use Test::Simple tests => 3; ok !open(my $fh, '|-', 'nonexistent program'), 'string form of open fa +ils'; ok open(my $prince, '|-', 'nonexistent program 2>/dev/null'), 'but suc +ceeds if shell uses redirection'; ok !open(my $none, '|-', 'nonexistent', 'program'), 'list form of open + fails, as it should'; __END__ 1..3 ok 1 - string form of open fails ok 2 - but succeeds if shell uses redirection ok 3 - list form of open fails, as it should
But why does string form of open correctly fail in the first test? Perl is able to process a simple command without help of a shell, as strace shows:
Stream redirection, however, requires a shell:$ strace -f -e clone,execve perl -e'open(my $fh, "|-", "nonexistent pr +ogram")' execve("/usr/bin/perl", ["perl", "-eopen(my $fh, \"|-\", \"nonexisten" +...], [/* 45 vars */]) = 0 clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIG +CHLD, child_tidptr=0xb74f7a68) = 7792 Process 7792 attached [pid 7792] execve("/home/aitap/perl5/bin/nonexistent", ["nonexistent" +, "program"], [/* 45 vars */]) = -1 ENOENT (No such file or directory +) [pid 7792] execve("/home/aitap/scripts/nonexistent", ["nonexistent", +"program"], [/* 45 vars */]) = -1 ENOENT (No such file or directory) [pid 7792] execve("/home/aitap/bin/nonexistent", ["nonexistent", "pro +gram"], [/* 45 vars */]) = -1 ENOENT (No such file or directory) [pid 7792] execve("/usr/local/bin/nonexistent", ["nonexistent", "prog +ram"], [/* 45 vars */]) = -1 ENOENT (No such file or directory) [pid 7792] execve("/usr/bin/nonexistent", ["nonexistent", "program"], + [/* 45 vars */]) = -1 ENOENT (No such file or directory) [pid 7792] execve("/bin/nonexistent", ["nonexistent", "program"], [/* + 45 vars */]) = -1 ENOENT (No such file or directory) [pid 7792] execve("/usr/local/games/nonexistent", ["nonexistent", "pr +ogram"], [/* 45 vars */]) = -1 ENOENT (No such file or directory) [pid 7792] execve("/usr/games/nonexistent", ["nonexistent", "program" +], [/* 45 vars */]) = -1 ENOENT (No such file or directory) [pid 7792] +++ exited with 1 +++ --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=7792, si_uid +=1000, si_status=1, si_utime=0, si_stime=0} --- +++ exited with 0 +++
Edit: spelling$ strace -f -e clone,execve perl -e'open(my $fh, "|-", "nonexistent pr +ogram 2>/dev/null")' execve("/usr/bin/perl", ["perl", "-eopen(my $fh, \"|-\", \"nonexisten" +...], [/* 45 vars */]) = 0 clone(Process 7809 attached child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, +child_tidptr=0xb753ea68) = 7809 [pid 7809] execve("/bin/sh", ["sh", "-c", "nonexistent program 2>/dev +/null"], [/* 45 vars */]) = 0 [pid 7809] +++ exited with 127 +++ --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=7809, si_uid +=1000, si_status=127, si_utime=0, si_stime=0} --- +++ exited with 0 +++
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Re^2: Can't close pipe to invalid process
by BrowserUk (Patriarch) on Aug 29, 2015 at 19:18 UTC | |
by aitap (Curate) on Aug 29, 2015 at 19:38 UTC | |
by BrowserUk (Patriarch) on Aug 29, 2015 at 19:59 UTC | |
by aitap (Curate) on Aug 31, 2015 at 12:34 UTC | |
by cLive ;-) (Prior) on Aug 31, 2015 at 15:04 UTC | |
by BrowserUk (Patriarch) on Aug 31, 2015 at 16:25 UTC |
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