CODEWITHSUNDEEP
linuxbashshellpipe
Bentley4
Bentley4

Reputation: 11028

How to not output anything when the first command of a pipe does not output

I have 2 commands which I want to pipe like so: command1 | command2. When command1 does not output anything at all command2 still outputs. How do I stop command1 | command2 from outputting when command1 does not output anything?

Concrete example:

function find_string_in_file {
find . -iname "*$1*" | xargs ack-grep "$2"
}
alias findag='find_string_in_file'

If filename.py does not exist in the current directory or its subfolders then findag filename.py "some word" still returns the same output as ack-grep "some word".

Upvotes: 1

Views: 218

Answers (2)

Explosion Pills
Explosion Pills

Reputation: 191749

You can change how you use xargs to require ack-grep to read arguments in line instead of through the pipe. This will work as you expect

find . -iname "*$1*" | xargs -I{} ack-grep "$2" {}

Upvotes: 1

chepner
chepner

Reputation: 531165

Pipes are not conditional, so you can't disable later stages based on the exit status of previous stages. For your particular example, you can modify the find command to avoid the need for a pipeline.

find . -iname "*$1*" -exec ack-grep "$2" '{}' +

If there are no matching files, the exec test won't be triggered.

Upvotes: 4

Related Questions