bin/177674: /bin/sh 'while read X' loop problem
root at ai1.alaska.net
Sat Apr 6 20:40:00 UTC 2013
>Synopsis: /bin/sh 'while read X' loop problem
>Arrival-Date: Sat Apr 06 20:40:00 UTC 2013
>Originator: Joe Public
>Release: FreeBSD 9.1-RELEASE i386
System: FreeBSD 9.1-RELEASE FreeBSD 9.1-RELEASE #0 r243826: Tue Dec 4 06:55:39 UTC 2012 root at obrian.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC i386
There is some kind of problem with 'read' in a sh(1) loop,
but it is only demonstrated with some programs (such as mplayer).
First, create a file with some valid MP3 pathanmes inside, then:
OK: while read X; do echo $X; done < FILEWITHMP3PATHNAMES
OK: while read X; do ls -l $X; done < FILEWITHMP3PATHNAMES
FAIL: while read X; do mplayer $X; done < FILEWITHMP3PATHNAMES
This last command line will fail in a mess of corruption,
and it is difficult to explain what is actually occurring.
With only 1 pathname in the file, it works OK, but with 2
or more, it increasingly results in more and more corruption.
I don't know what the problem is. I tried inserting sleep(1)
commands to make the loop slow and other things, but nothing
made any difference.
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