Bug 31836
| Summary: | When killed Perl should flush output buffers | ||
|---|---|---|---|
| Product: | Base System | Reporter: | Alejandro Forero Cuervo <bachue> |
| Component: | bin | Assignee: | freebsd-bugs (Nobody) <bugs> |
| Status: | Closed FIXED | ||
| Severity: | Affects Only Me | ||
| Priority: | Normal | ||
| Version: | 4.4-RELEASE | ||
| Hardware: | Any | ||
| OS: | Any | ||
State Changed
From-To: open->closed
> When the Perl interpreter is killed with SIGINT or SIGTERM (and
> probably many other trappable signals), it doesn't flush its output
> buffers.
It should not. If you want this functionality, set your own signal
handlers ($SIG{INT} = sub { ... }; $SIG{TERM} = sub { ... };). It is
not the job of the interpreter to do this. Perl, just like C, uses
stdio, which is buffered by default. In C, just like in Perl, you will
have to set your own signal handlers if you want to flush the buffers on
a signal.
|
When the Perl interpreter is killed with SIGINT or SIGTERM (and probably many other trappable signals), it doesn't flush its output buffers. By default, when someone calls Perl's print function, it performs unbuffered writes. When a Perl script exits, Perl does the right thing: it flushes the output buffers. However, when the Perl interpreter is killed, it doesn't flush them. This is confusing to many users (I just helped one in the spanish users' mailing list) and forces them to call the autoflush method from IO::Handle or set $| to 1 (to disable buffering) when all they really want is just to have their streams flushed. This doesn't affect GNU/Linux (Debian using Perl 5.6.0). However, I have tested it in OpenBSD and (unsurprisingly) it is also affected. The Perl interpreter should catch most (all? Hmm, what happens with SIGSEGV or SIGBUS? Hmm) trapable signals and automagically flush output buffers when they are about to cause program termination. I'm not sure if this is the right place to report this problem. If I'm doing something wrong, please forgive me and let me know so, in my efforts to help FreeBSD, I no longer do it in the future. Fix: This doesn't fix the problem but is what the users have to do to get around it: add $|=1; at the beginning or their scripts or use IO::Handle's autoflush method. How-To-Repeat: The following Perl script should illustrate well what happens: for ($i = 0; $i ne 10; $i ++) { sleep(1); print "!"; } When the user runs it, it exits after 10 seconds and the Perl interpreter flushes the output buffer so the user sees "!!!!!!!!!!". However, if the user interrupts the script (by, for instance, pressing C-c), Perl does not flush the output buffer and the user sees nothing.