Highlight Text Similar to Grep, But Don't Filter Out Text

Highlight text similar to grep, but don't filter out text

Use ack. Checkout its --passthru option here: ack. It has the added benefit of allowing full perl regular expressions.

$ ack --passthru 'pattern1' file_name

$ command_here | ack --passthru 'pattern1'

You can also do it using grep like this:

$ grep --color -E '^|pattern1|pattern2' file_name

$ command_here | grep --color -E '^|pattern1|pattern2'

This will match all lines and highlight the patterns. The ^ matches every start of line, but won't get printed/highlighted since it's not a character.

(Note that most of the setups will use --color by default. You may not need that flag).

Colorized grep -- viewing the entire file with highlighted matches

Here are some ways to do it:

grep --color 'pattern\|$' file
grep --color -E 'pattern|$' file
egrep --color 'pattern|$' file

The | symbol is the OR operator. Either escape it using \ or tell grep that the search text has to be interpreted as regular expressions by adding -E or using the egrep command instead of grep.

The search text "pattern|$" is actually a trick, it will match lines that have pattern OR lines that have an end. Because all lines have an end, all lines are matched, but the end of a line isn't actually any characters, so it won't be colored.

To also pass the colored parts through pipes, e.g. towards less, provide the always parameter to --color:

grep --color=always 'pattern\|$' file | less -r
grep --color=always -E 'pattern|$' file | less -r
egrep --color=always 'pattern|$' file | less -r

Negative matching using grep (match lines that do not contain foo)

grep -v is your friend:

grep --help | grep invert  

-v, --invert-match select non-matching lines

Also check out the related -L (the complement of -l).

-L, --files-without-match only print FILE names containing no match

grep highlights on screen but doesn't redirect to output

For reasons not known to me, the following command works directly.
Just FYI.

$fgrep -f pattern_list.txt data.txt 

Not "grep" but "fgrep".
Thanks for your interest and time.

How can I exclude one word with grep?

You can do it using -v (for --invert-match) option of grep as:

grep -v "unwanted_word" file | grep XXXXXXXX

grep -v "unwanted_word" file will filter the lines that have the unwanted_word and grep XXXXXXXX will list only lines with pattern XXXXXXXX.

EDIT:

From your comment it looks like you want to list all lines without the unwanted_word. In that case all you need is:

grep -v 'unwanted_word' file

Grep without filtering

If all you want to do is set the exit code if a pattern is found, then this should do the trick:

awk -v rc=1 '/pattern/ { rc=0 } 1; END {exit rc}' 

The -v rc=1 creates a variable inside the Awk program called rc (short for "return code") and initializes it to the value 1. The stanza /pattern/ { rc=0 } causes that variable to be set to 0 whenever a line is encountered that matches the regular expression pattern. The 1; is an always-true condition with no action attached, meaning the default action will be taken on every line; that default action is printing the line out, so this filter will copy its input to its output unchanged. Finally, the END {exit rc} runs when there is no more input left to process, and ensures that awk terminates with the value of the rc variable as its process exit status: 0 if a match was found, 1 otherwise.

The shell interprets exit code 0 as true and nonzero as false, so this command is suitable for use as the condition of a shell if or while statement, possibly at the end of a pipeline.

Grep highlight a pattern other than the searched one

Just grep again for the pattern you want to highlight:

cat log | grep 'status":"1' | grep '"email":"[^"]*"'

How can I grep recursively, but only in files with certain extensions?

Just use the --include parameter, like this:

grep -inr --include \*.h --include \*.cpp CP_Image ~/path[12345] | mailx -s GREP email@domain.example

That should do what you want.

To take the explanation from HoldOffHunger's answer below:

• grep: command

• -r: recursively

• -i: ignore-case

• -n: each output line is preceded by its relative line number in the file

• --include \*.cpp: all *.cpp: C++ files (escape with \ just in case you have a directory with asterisks in the filenames)

• ./: Start at current directory.

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