shell pipe "loses" parts of the data, was: help needed to debug Perl script

[Ralf Mardorf]

On Wed, 17 Oct 2018 19:05:23 +0200, Ralf Mardorf wrote:
>On Wed, 17 Oct 2018 18:36:18 +0200, M. Fioretti wrote:
>>b) AND the data also contained, for the first time, non-ascii
>>characters that make grep fail unless the -a option is used
>>
>>I am not sure at all of what I have just written, and every comment,
>>and tip to make sure this does not happen again in some future script
>>is very welcome.  
>
>even 'grep -a' could return undesired output. A way to workaround this
>issue might be using the 'strings' command and than piping through
>'grep'.
>
>[rocketmouse at archlinux ~]$ grep -a
>SOURCE /var/log/journal/a243f4e05c294b13ab6972bf4ff93907/system.journal
>| tail -1
>_SOURCE_REALTIME_TIMESTAMP=1539795805565362��R��q�ox!�b���_��I���t'��޿�v�|����8�&�������8���G��H�8�Qk��|���?
>[rocketmouse at archlinux ~]$
>strings /var/log/journal/a243f4e05c294b13ab6972bf4ff93907/system.journal
>| grep SOURCE | tail -1 _SOURCE_REALTIME_TIMESTAMP=1539795805565362
>[rocketmouse at archlinux ~]$

PS:

Sure, without the '-a' option 'grep' might not return any text contained
by the file [1]. Perhaps 'strings' does filter output you want to get.

Since we don't know what you actually try to achieve, we only could
provide shots in the dark. Perhaps 'grep -a' does always the trick for
you, while 'strings' might fail regarding your needs.

[1]
[rocketmouse at archlinux ~]$ grep SOURCE /var/log/journal/a243f4e05c294b13ab6972bf4ff93907/system.journal | tail -1
Binary file /var/log/journal/a243f4e05c294b13ab6972bf4ff93907/system.journal matches
[rocketmouse at archlinux ~]$