chris01
0
I want to output the captured group only.
input.txt
1xax1
1ybby1
9xcccx9
Command
perl -ne "/^.*x(.+)x.*$\// && print $1" input.txt
Output is all matching lines.
1xax1
9xcccx9
But I would expect ouly the captured group.
a
ccc
How to change my command??
Use single quotes (') around your script rather than double quotes ("):
perl -ne '/^.*x(.+)x.*$\// && print $1'
With double quotes, your shell interpolates $1 (which happens to be empty), so the one-liner that Perl receives is actually:
/^.*x(.+)x.*$\// && print
And print without arguments prints $_, which is the whole line.
Additionally, the current output of your script (with the single quotes) is:
accc
In order to easily add new lines, you could use the -l flag:
perl -nle '/^.*x(.+)x.*$/ && print $1' input.txt
which nicely outputs:
a
ccc
Incidentally, this will fix a bug with your current .*$\/: if the input file isn't finished by a newline, then your regex won't match the last line (because $\ is a newline here). But, even better to solve this last issue: you can omit the last part of your regex entirely (.*$\/ or .*$), since it doesn't change the outcome of the match (well, .*$\/ is buggy so it changes the outcome, but you get the idea):
perl -nle '/^.*x(.+)x/ && print $1'