Perl one-liner if else logic

Question

I'm evaluating whether or not certain variables match expected values. The variables are set in memory by a certain program, the values of which can be access from the shell with a custom program.

I'm piping the output of the shell command to awk to get the specific field I want and then I want to run it through perl to see if it matches the expected value. For example,

ysgrp autostart | awk -F\: '{print $1}' | perl -e 'print {"True"} else {print "False"} if /on/'

However, I'm getting complaints from perl about compilation errors near "} else". How does one handle if/then/else logic in a perl one-liner?

Answer 1

You can't use an else condition in a postfix conditional. You can either use a ternary conditional operator like this:

perl -e 'print /on/ ? "True" : "False"'

Or use explicit blocks like this:

perl -e 'if ( /on/ ) { print "True" } else { print "False" }'

Answer 2

This part:

awk -F\: '{print $1}' | perl -e 'print {"True"} else {print "False"} if /on/'

can be handled in perl (if I remember awk correctly):

perl -F/:/ -lane 'print $F[0] =~ /on/ ? "True" : "False"'

Note the use of the -n switch, without which your perl one-liner will not work. Also note the -l switch, which adds a newline to your print, which is something I assume you want. Otherwise your output will be something like:

TrueTrueTrueFalseTrueFalse

Answer 3

You could do:

 ... | perl -ne 'print /on/ ? "True" : "False"'

but please don't! You'd be better off doing:

... | grep -qF on && echo True || echo False