Re: Need Help: Capture Print Outputs from a Function

I found this by doing a supersearch.

#!/usr/bin/perl

use strict;
use warnings;

my ($buf);
{
  local *STDOUT;
  open( STDOUT, '>', \$buf ) or die "Write to buffer failed\n";
  mysub();
}

print "buffer: $buf\n";

sub mysub{
  print "mysub output\n";
}
[download]

Output:

---------- Capture Output ----------
> "C:\Perl\bin\perl.exe" _new.pl
buffer: mysub output


> Terminated with exit code 0.
[download]

Does that help?

Update: The above requires 5.8 (thanks to ikegami for pointing that out).

Comment on Re: Need Help: Capture Print Outputs from a Function Select or Download Code

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Re^2: Need Help: Capture Print Outputs from a Function by mnj200g (Novice) on May 02, 2006 at 18:05 UTC
It does not seem to be working. I get the following message: Use of uninitialized value in concatenation (.) or string at scop/x.pl line 126. buffer: Line 126 is where print "buffer: $buf\n"; is. Also, what is the structure under my ($buf); in your code? Is that how PERL creates a macro or what C calls prototypes? I've also tried the first method mentioned above and that also fail to initialize the variable $var. In that first function, what is the significant of "qw"? Thanks.	[reply]
Re^3: Need Help: Capture Print Outputs from a Function by ikegami (Patriarch) on May 02, 2006 at 18:19 UTC
I get the following message: Use of uninitialized value in concatenation (.) You're using a version of Perl older than 5.8.0, when `open(STDOUT, '>', \$buf)` was introduced. Before 5.8, `\$buf` would be stringified to something like `SCALAR(0x1ab2760)`. The output ends up in a file by that name instead of going to `$buf`, so `$buf` is still undefined when you go to inspect it. Before 5.8, you had to use IO::String or IO::Scalar. Also, what is the structure under my ($buf); in your code? It creates a new scope. This causes `local STDOUT;` to be undone (thus restoring the original STDOUT) before the last `print`. what is the significant of "qw"* `qw[ some args here ]` is the same thing as `('some', 'args', 'here')` See perlop.	[reply] [d/l] [select]
Re^3: Need Help: Capture Print Outputs from a Function by wfsp (Abbot) on May 02, 2006 at 18:22 UTC
I updated my node to point out that perl 5.8 is required for that to work (apologies for the delay). Which version of perl are you using?	[reply]
Re^4: Need Help: Capture Print Outputs from a Function by mnj200g (Novice) on May 02, 2006 at 18:58 UTC
wfsp. Thank you for your patience. Being a beginner, I appreciate yours and everyone else's help and patience. Anyway, the code is working as a stand alone so I must be introducing something else that it does not like. My PERL version is listed as 5.008005 in SunOS 5.8. On the subject of a new scope. Does that mean I should do the following: `sub1() { my $variables; my $buff; code code code { local *STDOUT; open( STDOUT, '>', \$buf ) or die "Write to buffer ailed\n"; mysub(); } print "buffer: $buf\n"; more code } sub mysub { print "mysub output\n"; }` [download] Again, thanks. MNJ	[reply] [d/l]
Re^2: Need Help: Capture Print Outputs from a Function by mnj200g (Novice) on May 03, 2006 at 01:01 UTC
Thank you again to everyone. It is working. I did ran into the problem mentioned by BrowserUK where another function using select(STDOUT) and then setting "$\| = 1;" (no buffering). That gave me the problem of $buf coming back empty. I fixed that by setting buffer on ($\| = 0) just before the local "scope". Again, thank you. MNJ	[reply]