I am trying to print all files in /usr/bin/ where the filename starts with a v. This works,
ls -lA /usr/bin/ | awk '{print $9}' | grep ^v
Surprisingly, this returns no output,
ls -lA /usr/bin/ | awk '/^v/ {print $9}'.
I don’t understand the difference. I am running Ubuntu 21.10 with awk -W version saying that it is on 1.3.4 20200120.
Edit: I understand that awk may not be the best way to accomplish what I am wanting to do here. But, this is an exercise in learning awk by testing my understanding via comparing it to the real output.
>Solution :
The difference between the two pipelines is that the first outputs the 9th column and then check to see if that starts with a v the second checks to see if the line starts with a v, change the second to:
$ ls -lA /usr/bin/ | awk '$9 ~ /^v/ {print $9}'
When writing:
/pattern/ { ... }
it’s the same as writing
$0 ~ /pattern/ { ... }
but in your case you want to compare the 9th column, so write that instead.
But you really don’t want to create a pipeline for this, and what would happen if your files contain a space?
You can consider using find or globs instead:
$ printf '%s\n' /usr/bin/v*
/usr/bin/vi
/usr/bin/view
...
or
$ find /usr/bin -name 'v*' -print
/usr/bin/vi
/usr/bin/view
...