Grep text only only after [word]:

Question

I have a file example.txt which contains following text:

[one]: bla bla bla onebla twobla
[two]: hey heya noheya
[onemore]: i got mad and etc

I need to grep and show only text that after [myword]: Tried to test it this way:

grep [myword] /tmp/example.txt | cut -d ':' -f 2

On each [myword] it prints all after brackets, but how can I get only the one I need only and not all?

I need to print only the test that after certain brackets. For example I want to print only text that in line [one]: but not after [two]: or [onemore]:lines, so that the output will be bla bla bla onebla twobla. If I want to print all after [onemore]: - the correct output should be i got mad and etc

Answer 1

Better with sed:

sed -n 's/^\[one]: //p' < example.txt

With GNU grep with support for recent PCRE, you can also do:

grep -Po '^\[one]: \K.*' < example.txt

Or

grep -xPo '\[one]: \K.*' < example.txt

In any case, note that in most shells, [...] are glob operators. In grep [myword], [myword] is expanded to the list of files that match that, that is any file in the current directory whose name is m, y, w, o, r or d (and if there's none, depending on the shell, the pattern is passed as-is to grep, or you get an error). So they must be quoted for the shell (with single quotes for instance as in the solutions here). For instance, if there's a file called r in the current directory, and one called d, grep [myword] would become grep d r in all shells but fish.

[...] is also a special operator in regular expressions (very similar to the [...] glob operator), grep '[myword]' would match on lines that contain m, y, w, o, r or d. So you need to escape the opening [ for grep (for regular expressions) as well. That can be done with grep '\[myword]' or grep '[[]myword]'.

^ is another regular expression operator that means: match at the beginning of the line only. So grep '^\[myword]: ' matches on lines that start with [myword]:.

While grep is just meant to print matching lines (is not otherwise a stream editor like sed is), GNU grep added the non-standard -o option for it to print the matching portion(s) of the line (if non-empty). It also added the -P options to use perl compatible regular expressions (in PCRE) instead of basic ones without -P.

In recent PCREs, \K is an operator that resets the start of the matching portion. So in grep -Po '^\[one]: \K.*', we do print the matching portion because of -o, but because of \K, that matching portion becomes the sequence of characters (.*) that is found after [one]:.

Answer 2

If you wish the solution which is independent on a delimiter, the use awk

$ cat 304162 
[one]: bla bla bla onebla twobla
[two]: hey heya noheya
[onemore]: i got mad and etc
[fourth:one]: some more bla, well ! worst case
$ awk '/\[onemore\]/{sub(/^[^]]*\]:[[:blank:]]*/,"");print}' 304162
i got mad and etc
$ awk '/\[fourth:one\]/{sub(/^[^]]*\]:[[:blank:]]*/,"");print}' 304162
some more bla, well ! worst case

Answer 3

[one] regular expression means "a character matching o or n or e.
grep [one] /tmp/example.txt will match all the lines of your example

To match the [] as characters you need to escape them :

grep \\[one\\] /tmp/example.txt   | cut -d ':' -f 2

Or you can use grep -F which ignore the regular expression syntax :

grep -F [one] /tmp/example.txt | cut -d ':' -f 2