I want to run b.pl, where b.pl is:

select(STDERR);$|=1;select(STDOUT);$|=1;   # autoflush
print "This is the prompt: ";
my $input = <STDIN>;
print "done.\n";

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This works:

select(STDERR);$|=1;select(STDOUT);$|=1;   # autoflush
$cmd = 'perl b.pl 2>&1';
system($cmd);

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But I want to capture the output into a log file in addition to displaying it on the screen. This, annoyingly, does not show the prompt until after you press RETURN to an empty screen:

select(STDERR);$|=1;select(STDOUT);$|=1;   # autoflush
$cmd = 'perl b.pl 2>&1 |';
open(CMD, $cmd) or die "error: open '$cmd': $!\n";
while (<CMD>) { print }  # and print to log file here too
close(CMD);

[download]

This works:

select(STDERR);$|=1;select(STDOUT);$|=1;   # autoflush
$cmd = 'perl b.pl 2>&1 | tee -a logfile.txt';
system($cmd);

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But I would prefer not to rely on the availability of tee command. Please help.

In reply to Command output to screen and logfile buffering problem by eyepopslikeamosquito

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