02-12-2009
Breaking out of a pipe
I have the following command in a Bash shell script:
who | grep -w $1 | some other commands
If grep fails, an error message is displayed. How do I test if grep fails and still be able to pipe it's output to the rest of the commands?
I have the following solution:
a=`who | grep -w $1`
if [ $? -eq 0 ]
then
display error message
fi
printf "$a" | some other commands
Is this the best solution, or is there another method?
Just in case I have some other set of commands, and the variable is assigned some other output, I read somewhere that its not a good idea to assign variables to a large amount of data, or binary data.
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ZGREP(1) General Commands Manual ZGREP(1)
NAME
zgrep - search possibly compressed files for a regular expression
SYNOPSIS
zgrep [ grep_options ] [ -e ] pattern filename...
DESCRIPTION
Zgrep invokes grep on compressed or gzipped files. These grep options will cause zgrep to terminate with an error code:
(-[drRzZ]|--di*|--exc*|--inc*|--rec*|--nu*). All other options specified are passed directly to grep. If no file is specified, then the
standard input is decompressed if necessary and fed to grep. Otherwise the given files are uncompressed if necessary and fed to grep.
If the GREP environment variable is set, zgrep uses it as the grep program to be invoked.
EXIT CODE
2 - An option that is not supported was specified.
AUTHOR
Charles Levert (charles@comm.polymtl.ca)
SEE ALSO
grep(1), gzexe(1), gzip(1), zdiff(1), zforce(1), zmore(1), znew(1)
ZGREP(1)