Re: parsing Makefiles

[Andrew Gaffney]

David le Blanc wrote:
From: Andrew Gaffney [mailto:[EMAIL PROTECTED] 
Sent: Sunday, 22 February 2004 6:09 PM
To: David le Blanc
Cc: [EMAIL PROTECTED]
Subject: Re: parsing Makefiles

David le Blanc wrote:

I've come up with some *simple* code that seems to work:

#!/usr/bin/perl

use strict;
use warnings;
$| = 1;
my $total = `make -n | wc -l`;
my ($count, $line);
open MAKE, "make |";
foreach $line (<MAKE>) {
 $count++;
 my $percent = int(($count / $total) * 100);
 print "..$percent";
}


You may find that the 'MAKE' file handle is buffered by the make
application.
I order to ensure 'make' doesn't buffer its output, you 
need to run it

in its
own pseudo-terminal.   The Expect module may be able to 
help, since it

runs
apps in pseudo-terminals, or someone else may offer a 
better solution.

Its not the 'make' output that's being buffered. That doesn't 
get printed at all. Its my 
output that does appear until the whole run is done.
Ok,  Lets break down what is really going on here.

Your  loop construct:

foreach $line (<MAKE>) {
        .. print stuff ..
}

is looping BASED ON THE OUTPUT of the make command.  

Since the MAKE COMMAND OUTPUT is being buffered by the make command,
you will find that NOTHING arrives in the 'foreach' loop until the
entire 
make has complete and FLUSHED its output.

Hence, if you want to print output as the MAKE COMMAND OUTPUT arrives,
you
must make sure the COMMAND OUTPUT arrives in a timely manner.. I.e.
unbuffered.
I understand. I modified my code to verify this:

#!/usr/bin/perl

use strict;
use warnings;
#$| = 1;
my $total = `make -n | wc -l`;
print "$total\n";
my ($count, $line);
open MAKE, "make |";
foreach $line (<MAKE>) {
  $count++;
  my $percent = int(($count / $total) * 100);
#  print "..$percent";
  print $line;
}
This waited until the end to print all the output. Although, if I do something like 'make 
| less' on the command line, the output is not buffered. So, is Perl buffering the output 
from MAKE in this case?

--
Andrew Gaffney
Network Administrator
Skyline Aeronautics, LLC.
636-357-1548
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