UNIX for Dummies Questions & Answers

Hi all,

I just downloaded this example from the net. I was looking around for a hash table like implementation in unix when I came across this.

Code:

ARRAY=( "cow:moo"
        "dinosaur:roar"
        "bird:chirp"
        "bash:rock" )

for animal in ${ARRAY[@]} ; do
    KEY=${animal%%:*}
    VALUE=${animal##*:}
    printf "%s likes to %s.\n" $KEY $VALUE
done

Can anyone please help me how does the ${animal%%:*} match to cow , is it a regular expression ?

Thanks in advance ...

No, just a ksh substring feature, using file globbing wild cards with meta characters '*', '?', '[...]' but not '[^...]', not regex. It says get the value of animal and chew the end aggressively so as to find the first ':' with the '*'. The '%' means chew on right end, mnemonic: get your percent in the end. # means pound on the nose, chew on the left end. Double ##/%% takes the * from lazy to aggressive. In these cases, aggressive was unnecessary.

Thanks a lot DGPickett for the response,

Actually I am using bash ( /bin/sh ) , so does this work in bash too ...

bash most definitely is not /bin/sh except by coincidence on some systems. If you're using bash features, use #!/bin/bash, not #!/bin/sh. On some systems this difference is vital.

Hi Corona688,

Thanks for your reply. In the system that I use we have /bin/sh pointing to bash.

[ais@nm11of05 bin]$ ls -l sh
lrwxrwxrwx 1 root root 4 Jun 3 2010 sh -> bash
[ais@nm11of05 bin]$ pwd
/bin

Like I said, that's only a coincidence. If you move this script to another system it could well break. If you're using bash's features, always use #!/bin/bash. The purpose of that is to warn people that this script needs bash! Otherwise they won't know why it's breaking.

Careful, bash may act somewhat like sh when sh is the called program name.