Bash: grep pattern from command output

Question

I\'m really new with bash, but it\'s one of the subjects on school. One of the exercises was:

Give the line number of the file \"/etc/passwd\" where the informat

Answer 1

Check command substitution in the bash man page.

You can you back ticks `` or $() , and personally I prefer the latter.

So for your question:

grep -n -e $(whoami) /etc/passwd | cut -f1 -d :

will substitute the output of whoami as the argument for the -e flag of the grep command and the output of the whole command will be line number in /etc/passwd of the running user.