[CALUG] More I/O buffering foolishness

[Allbritten, Mark]

Hi Jason, 
Perl is taking standard in as one chunk.  I believe you need to use a while readline loop...  But if that's all your using perl for it would be easier to do something like:
while read X ^Jdo^Jecho $X^Jdone 
I don't have a perl while readline snippet handy..... 
Best Regards, 
Mark 


-----Original Message-----
From: lug-bounces at calug.com [mailto:lug-bounces at calug.com]On Behalf Of Jason C. Miller
Sent: Wednesday, March 01, 2006 9:43 AM
To: lug at calug.com
Subject: [CALUG] More I/O buffering foolishness

I've asked a buffering question on here before and have now run into a
similar-yet-different issue and was wondering if anyone had any insight.

Here's the short story...


At the command line (bash) ...
-----------------------------------
(cd /blah ; tar cvf - * 2>/dev/null) | (cd /blah2 ; tar xvf - 2>/tmp/log) | \
perl -e 'while (<STDIN>) { print }'
-----------------------------------
... works fine.  All it does is print the stdout from the tar extraction. 


However, once inserted into a script, the exact same string of commands
will be block-buffered instead of line-buffered (ie. prints output in
chunks).  Granted, this isn't unheard of.  This is particularly annoying
because the stdin is being used as input for another program (Xdialog).  


The oddness is that, inside the script ...
-----------------------------------
(cd /blah ; tar cvf - * 2>/dev/null) | (cd /blah2 ; tar xvf - 2>/tmp/log)
-----------------------------------
... will line-buffer just fine.  It's when I try to pipe that into
anything else AFTER that the buffering issues come up.  I've tried it with
both perl and awk and they both do the same thing.  I tried forcing the
flush in the perl, but that doesn't do anything and I really don't know if
that's the issue or not. 


Any ideas?

                                           -jason

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