comment on

Hi,

I know that questions about progress bars have been answered here before, but they did not seem to address my special case here (forgive me if I'm wrong). Anyway, I tried to roll my own solution that works partly, but I ran into some trouble.

Here's what I try to achieve:

run an external command (e.c.) and dispaly some kind of "notification" to the user (that - yes - has nothing to do with how "far" the e.c. actually is)

capture output AND exit value from the e.c.

the current design is as follows

the sub forks.

the child runs the command via open-pipe

the parent outputs some kind of progress bar

child communicates output and exit value via pipes to the parent

parent outputs the retrieved stuff after the child has exited

My code works fine for some commands, but - for whatever reason - not for all of them.

($result, $exitcode) = run_w_progress(1, 'for i in `seq -w 4`; do slee
+p 3; /bin/echo $i; done');
[download]

returns

Result:
1
2
3
4

Exitcode:0
finishing ...
[download]

whereas

($result, $exitcode) = run_w_progress(1, '/bin/echo -e "foo\nbar"');
[download]

only returns (note the missing 'bar')

Result:
foo

Exitcode:0
finishing ...
[download]

Here's my code (fully working example):

#!/usr/bin/perl                                  
 
use strict;
use warnings;
use POSIX ":sys_wait_h";
use IO::Select;         
use IO::Handle;         

my ($result, $exitcode) = run_w_progress(1, 'for i in `seq -w 4`; do s
+leep 3; /bin/echo $i; done');
print "Result:\n",$result,"\nExitcode:",$exitcode,"\n";               
+                             

($result, $exitcode) = run_w_progress(1, '/bin/echo -e "foo\nbar"');
print "Result:\n",$result,"\nExitcode:",$exitcode,"\n";             

sub run_w_progress {
        my ($sleep, $cmd) = @_;
        my($reader, $writer);  
        pipe $reader, $writer;
        my($reader2, $writer2);
        pipe $reader2, $writer2;
        $writer->autoflush(1);
        $writer2->autoflush(1);
        my @watch = qw(| / - + \ | / - \ |);
        my $pos = 0;
        $|++;
        if ( fork()) {
                my $kid;
                my $output = '';
                my $exitval;
                my $c=0;
                my $handles = IO::Select->new();
                $handles->add($reader, $reader2);
                do {
                        sleep $sleep;
                        my @fhs;
                        while (@fhs = $handles->can_read(0)) {
                                for my $fh (@fhs){
                                        if (fileno($fh) == fileno($rea
+der)) {
                                                my $line = scalar <$re
+ader>;
                                                        $output .= $li
+ne;
                                        }
                                        else {
                                                        $exitval = sca
+lar <$reader2>;
                                                        chomp $exitval
+;
                                        }

                                }
                        }
                        print "\r",'|'x$pos,$watch[$c++];
                        if ($c == 10) {
                                $c=0;
                                $pos++;
                        }
                        $kid = waitpid(-1, WNOHANG);
                } until $kid > 0;
                print "|\n";
                return ($output, $exitval);
        }
        else {
                open(my $pipe, '-|', $cmd);
                while (<$pipe>) {
                        # pass output line to parent
                        print $writer $_;
                }
                close $pipe;
                close $writer;
                # pass exit value to parent 
                print $writer2 $?>>8, "\n";
                close $writer2;
                exit 0;
        }
}

print "finishing ...\n";
[download]

Any hints greatly appreciated!
svenXY

Todo: Make this also work with STDERR and such...

In reply to external command, progress bar and exit value by svenXY

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