NAME
Devel::Trace::Fork - Devel::Trace-like output for multi-process programs
VERSION
0.11
SYNOPSIS
perl -d:Trace::Fork program
DESCRIPTION
Like Mark Jason Dominus's Devel::Trace module, but debugging output includes additional information like
a high-resolution timestamp for the time each statement was executed
the process id of the process that executes each statement
the current value of the $CHILD_ERROR variable (
$?
)
This additional information can be helpful for debugging programs that make use of the fork system call to run. For example, the Trace::Fork
output of this program:
if (fork() == 0) {
print "This is the child.\n";
exit 0;
}
print "This is the parent.\n";
will be a file that looks something like:
/usr/bin/perl test
1268025451 1268025451.815
>> 0.816214:7996:0:test:1: if (fork() == 0) {
>> 0.826566:7996:0:test:5: print "This is the parent.\n";
>> 0.826684:9572:0:test:2: print "This is the child.\n";
>> 0.826941:9572:0:test:3: exit 0;
DETAILS
Debug output is not to STDERR
, but to a file that is either specified by $ENV{DTRACE_FILE}
or set to the file name "DTFork.$$"
in the current directory (where $$
is the process identifier of the parent process). To output debugging output to STDERR
the way Devel::Trace does, see Devel::Trace::Fork::Stderr.
See Devel::Trace. Use the $Devel::Trace::TRACE
variable or the Devel::Trace::trace
function exactly the way you would use them with the pure Devel::Trace
module. To import the Devel::Trace::trace
function into your program's namespace, include the line:
use Devel::Trace 'trace';
somewhere in your program.
SUBROUTINES/METHODS
None
DIAGNOSTICS
Devel::Trace::Fork: failed to ...
-
An I/O error occurred with the trace output file. Check that you have permission to create or overwrite the file specified by the
DTRACE_FILE
environment variable, or ifDTRACE_FILE
is not specified, that you can create files in the current directory.
CONFIGURATION AND ENVIRONMENT
$ENV{DTRACE_FILE}
-
Name of trace output file. If not specified, uses the filename
"DTFork.$$"
in the current directory. $ENV{DTFORK_ERASE_ON_GOOD_EXIT}
-
If this variable is non-zero, and the program is successful (that is, it is exiting with status 0), then the output trace file will be removed. This setting is helpful if you are trying to replicate an intermittent program failure and don't want your directory littered with the trace files of successful runs.
DEPENDENCIES
Devel::Trace
BUGS AND LIMITATIONS
If there are child processes that exit later than the parent process, then the final output will not be sorted.
There is almost enough information in the trace output to use it for profiling. Almost.
SEE ALSO
Devel::Trace, Devel::Trace::More
AUTHOR
Marty O'Brien, <mob@cpan.org>
LICENSE AND COPYRIGHT
Copyright (c) 2010, Marty O'Brien
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.0 or, at your option, any later version of Perl 5 you may have available.