My program has a Tk front end and allows users to invoke all sorts of functions via various widgets. If a function has a problem it can change the color of the LogFile widget to indicate trouble, and clicking the LogFile button opens the logfile for inspection.

I think I can live with all the functions dumping their various warnings and such into one file. My question is, if programs (under "my" control) are individually opening the logfile via '>>' for their error logging, what problems might I face? My goal is to interweave my log messages (via warn to a redirected STDERR) with any sort of system log messages.

As an example, the following program seems to "share" the file okay. What might beset me with this approach?

#!/usr/bin/perl -w
# show two concurrent processes intermingling their STDERR to the same
+ file.
# Name the program 'test_err.pl' and invoke it from command line with:
#    test_err.pl hs

use strict;

my $err_file = 'errfile.txt';
open STDERR, ">> $err_file"
    or die "cannot open initial $err_file:  $!\n";

my $what_to_do = shift;
warn "$what_to_do hello world\n";

system( 'test_err.pl', 'abc' )
    if $what_to_do eq 'hs';

my $test_string;
warn "success\n" if $test_string eq 'xyz';

warn "$what_to_do goodbye world\n";

# Adds the following text to 'errfile.txt':
__DATA__
hs hello world
abc hello world
Use of uninitialized value in string eq at C:\aa\test_err.pl line 19.
abc goodbye world
Use of uninitialized value in string eq at C:\aa\test_err.pl line 19.
hs goodbye world

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In reply to multiple programs sharing redirected STDERR by ff

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