GNU bug report logs - #8961
stdbuf has no effect on some programs

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Bruno Haible <bruno <at> clisp.org>
To: bug-coreutils <at> gnu.org
Subject: stdbuf has no effect on some programs
Date: Wed, 29 Jun 2011 22:59:13 +0200

Hi,

The glibc 'iconv' program buffers its input, and some people don't like this.
I thought that the 'stdbuf' program could remove the buffering, but it does not
work.

How to reproduce:

Create this script and make it executable:
================================== producer ==================================
#!/bin/sh
echo Hello
/bin/sleep 3
echo World
==============================================================================

$ ./producer | /usr/bin/iconv -f ASCII
Hello
World

All the output comes at the end.

$ stdbuf -o 0 ./producer | /usr/bin/iconv -f ASCII
Hello
World

All the output comes at the end.

$ ./producer | stdbuf -i 0 /usr/bin/iconv -f ASCII
Hello
World

All the output comes at the end.

$ stdbuf -o 0 ./producer | stdbuf -i 0 /usr/bin/iconv -f ASCII
Hello
World

All the output comes at the end.

What do I need to do to get the output of the first line immediately?

/usr/bin/iconv is from glibc, but I get the same behaviour from libiconv's
'iconv' program too.

In $ ./producer | /bin/cat
I get the first line immediately, but the coreutils documentation
<http://www.gnu.org/software/coreutils/manual/html_node/stdbuf-invocation.html>
makes me think that 'stdbuf' is meant for those programs that do not work like
'cat'.

Bruno
-- 
In memoriam José Olaya <http://es.wikipedia.org/wiki/José_Olaya>

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