Question

I have am trying to use sed to get some info that is encoded within the path of a file which is passed as a parameter to my script (Bourne sh, if it matters).
From this example path, I’d like the result to be 8

PATH=/foo/bar/baz/1-1.8/sing/song

I first got the regex close by using sed as grep:

echo $PATH | sed -n -e  "/^.*\/1-1\.\([0-9][0-9]*\).*/p"

This properly recognized the string, so I edited it to make a substitution out of it:

echo $PATH | sed -n -e "s/^.*\/1-1\.\([0-9][0-9]*\).*/\1/"

But this doesn’t produce any output. I know I’m just not seeing something simple, but would really appreciate any ideas about what I’m doing wrong or about other ways to debug sed regular expressions.

(edit)

In the example path the components other than the numerical one can contain numbers similar to the numeric path component that I listed, but not quite the same. I’m trying to exactly match the component that that is 1-1. and see what some-number is.

It is also possible to have an input string that the regular expression should not match and should product no output.

Answer 1

The -n option to sed supresses normal output, and since your second line doesn’t have a p command, nothing is output. Get rid of the -n or stick a p back on the end