Question

I have little problem with specifying my variable. I have a file with normal text and somewhere in it there are brackets [ ] (only 1 pair of brackets in whole file), and some text between them. I need to capture the text within these brackets in a shell (bash) variable. How can I do that, please?

Answer 1

Bash/sed:

VARIABLE=$(tr -d '\n' filename | sed -n -e '/\[[^]]/s/^[^[]*\[\([^]]*\)].*$/\1/p') 

If that is unreadable, here’s a bit of an explanation:

VARIABLE=`subexpression`      Assigns the variable VARIABLE to the output of the subexpression.  tr -d '\n' filename  Reads filename, deletes newline characters, and prints the result to sed's input  sed -n -e 'command'  Executes the sed command without printing any lines  /\[[^]]/             Execute the command only on lines which contain [some text]  s/                   Substitute ^[^[]*               Match any non-[ text \[                   Match [ \([^]]*\)            Match any non-] text into group 1 ]                    Match ] .*$                  Match any text /\1/                 Replaces the line with group 1 p                    Prints the line