Re: [gentoo-user] 'if echo hello' in .bashrc

[Christian <mcr76@gmx.net>]

Hi Alan,

Am Freitag, 8. Mai 2009 schrieb Alan McKinnon:
> > Some greps (like BSD one) might not support '--color' option, so "echo
> > hello|grep --color=auto l" will return error code, skipping if clause,
> > and won't break grep operation by adding an unsupported option.

is this really right?

The result of

if echo hello|grep --Acolor=auto l >/dev/null 2>&1; then echo hallo; fi

is nothing. So the if clause is false although I pieped STDERR to /dev/null.

> except that STDERR is combined with STDOUT and sent to /dev/null so the
> script will never get it, the if is always true and the entire check is
> redundant. Better would be
>
> if echo hello|grep --color=auto l >/dev/null ; then

grep writes to STDERR if an error is occured.

The result of 

 if echo hello|grep --Acolor=auto l >/dev/null ; then echo hallo; fi

is:
grep: Unbekannte Option »--Acolor=auto«
Aufruf: grep [OPTION]... MUSTER [DATEI]...
»grep --help« gibt Ihnen mehr Informationen.


Best regard
Christian