Public bug reported:

Binary package hint: p7zip

= expected behaviour =

7z(a) should be able to be used in pipe filters and thus to read from
stdin (-si) and write to stdout (-so). This works as long as only one of
these is used (e.g. 7z at begin or end of pipe). If you want both to
work together (e.g. in the middle of the pipe) 7z denies execution.

man 7z (same for 7za) documents the option as follows:

  -so    Write data to StdOut (eg: % echo foo | 7z a dummy -tgzip -si
-so > /dev/null)


= experienced behaviour =

However if you do this (same again for 7za):

  $ echo foo | 7z -a dummy -tgzip -si -so > testfile

Return value is 7 (bad command line) and testfile has the following
content (not compressed or something):


  Error:
  Incorrect command line

(It's furthermore noteworthy that an error message is written to stdout
while I want to have my actual data there - what's going to happen if 7z
encounters a bug while compressing - do I get my data stream corrupted
by a message then? But that's another issue)

= external bug tracking =

Bug exists since 7 years in the project's bug tracker:
http://sourceforge.net/tracker/?func=detail&aid=1627883&group_id=111810&atid=660493
. Debian has no references to this bug.


= resolution =

Maybe the feature could be marked as missing in the bug section of the
man page. The misleading example should vanish.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: p7zip-full 9.04~dfsg.1-1
ProcVersionSignature: Ubuntu 2.6.32-25.45-generic 2.6.32.21+drm33.7
Uname: Linux 2.6.32-25-generic x86_64
NonfreeKernelModules: fglrx
Architecture: amd64
Date: Sat Oct 30 15:14:40 2010
InstallationMedia: Ubuntu 9.10 "Karmic Koala" - Release amd64 (20091027)
ProcEnviron:
 PATH=(custom, user)
 LANG=sv_SE.utf8
 SHELL=/bin/bash
SourcePackage: p7zip

** Affects: p7zip (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug lucid

-- 
reading from stdin and at the same time writing to stdout does not work
https://bugs.launchpad.net/bugs/668727
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