Pipe grep exit code away

exitgreppipe

When I need to suppress some kind of output e.g.

foo | grep -v bar

But foo gives sometimes only:

bar
bar
bar...

grep will return -1. How do I transform the exit code 1 to 0?

Best Answer

You could always try piping it through something else, like cat, to get rid of the exit code from grep - though that may be a bigger hammer than you want.

Related Solutions

Grep multiline pattern

You could install pcregrep (available in most distro repositories) - which is grep using the pcre library, which does "Perl Compatible Regular Expressions". It has a command line option -M which allows you to do multiline searches - from the man page:

"The output for any one match may consist of more than one line."

So you could do

pcregrep -M 'my\s+ice\s+tea' filename

The \s is whitespace, which will match \n and \r in multiline mode, in addition to the normal whitespace characters. You can also match the newline character directly, so you could do

pcregrep -M 'pattern1_\n_pattern2' filename

How to retain grep’s match highlighting when piping find into grep

In both commands, the problem is that not grep but another command generates the actual output (xargs and find, respectively).

You can solve this by directly calling grep for each file name:

IFS=$'\n'
for FILE in $(find . -iname "*.abc"); do
    grep foo $FILE
done
unset IFS

Or as a one-liner:

IFS=$'\n';for FILE in $(find . -iname "*.abc");do grep foo $FILE;done;unset IFS

How it works:

IFS=$'\n' sets the internal field separator to the newline character (or spaces in file names will cause problems).
for FILE in $(COMMAND); do COMMANDS done loops through the files specified by COMMAND, sets the variable FILE to the current file and executes COMMANDS.
grep foo $FILE searches for foo in $FILE and sends the results directly to the screen.
unset IFS sets the internal field separator back to its default value (not needed in a script).

Best Answer

Related Solutions

Grep multiline pattern

How to retain grep’s match highlighting when piping find into grep

How it works:

Related Question