How do I best pass arguments to a Perl one-liner?

Question

I have a file, someFile, like this:

$cat someFile
hdisk1 active
hdisk2 active

I use this shell script to check:

Answer 1

Combining some of the earlier suggestions and adding my own sugar to it, I'd do it this way:

perl -se '/hdisk([$d])/ && print "$1: ok\n" for <>' -- -d='[value]' [file]

[value] can be a number (i.e. 2), a range (i.e. 2-4), a list of different numbers (i.e. 2|3|4) (or almost anything else, that's a valid pattern) or even a bash variable containing one of those, example:

d='2-3'
perl -se '/hdisk([$d])/ && print "$1: ok\n" for <>' -- -d=$d someFile 

and [file] is your filename (that is, someFile).

Answer 2

You can enable rudimentary command line argument with the "s" switch. A variable gets defined for each argument starting with a dash. The -- tells where your command line arguments start.

for d in 1 2 ; do 
  cat someFile | perl -slane ' print "$someParameter: OK" if /hdisk$someParameter\s+/' -- -someParameter=$d; 
done

See: perlrun

Answer 3

Pass it on the command line, and it will be available in @ARGV:

for d in 1 2
do
  perl -lne 'BEGIN {$d=shift} print "$d: OK" if /hdisk$d\s+/' $d someFile
done

Note that the shift operator in this context removes the first element of @ARGV, which is $d in this case.

Answer 4

That looks good, but I'd use:

for d in $(seq 1 2); do perl -nle 'print "hdisk$ENV{d} OK" if $_ =~ /hdisk$ENV{d}/' someFile; done

Answer 5

If you are having trouble writing a one-liner, maybe it is a bit hard for one line (just my opinion). I would agree with @FM's suggestion and do the whole thing in Perl. Read the whole file in and then test it:

    use strict;
    local $/ = '' ; # Read in the whole file
    my $file = <> ;

    for my $d ( 1 .. 2 )
    {
        print  "$d: OK\n" if  $file =~ /hdisk$d\s+/
    }

You could do it looping, but that would be longer. Of course it somewhat depends on the size of the file.

Note that all the Perl examples so far will print a message for each match - can you be sure there are no duplicates?

Answer 6

Sometimes breaking the Perl enclosure is a good trick for these one-liners:

for d in 1 2 ; do cat kk2 | perl -lne ' print "'"${d}"': OK" if /hdisk'"${d}"'\s+/';done