topic Re: shell script - how hard can it be in Operating System - HP-UX

shell script - how hard can it be

Adam Noble — Fri, 09 Feb 2007 07:10:38 GMT

Hi,

I simply want to use an if statement to see whether I should send the output of a command to my output file.

I'm using the following and only want to send the output to the file if the 1st 2 characters begin HP.

if [ $revision = "HP*" ];then

The above however doesn't work how do I do this.

Re: shell script - how hard can it be

Peter Godron — Fri, 09 Feb 2007 07:18:39 GMT

Adam,
how about:
if [ `expr substr "$revision" 1 2` = "HP" ]
then
.
.
fi

Re: shell script - how hard can it be

Ralph Grothe — Fri, 09 Feb 2007 07:22:27 GMT

It very much depends on the shell you are doing this in.
For instance shells such as Bash offer an expansion syntax which doesn't even require some external filter commands and yet let you extract a certain substring.
However, with HP posix shell you could do this
(but there are many other solutions conceivable)

(( $(expr "$revision" : ^HP) == 2 )) && echo do something

Re: shell script - how hard can it be

Ralph Grothe — Fri, 09 Feb 2007 07:29:47 GMT

Sorry, I made a mistake.
The correct terminology I was referring to when talking about Bash was "Parameter Substitution" and not "expansion".
But this is due to my English non-nativeness, I suppose.
And here's what I meant in Bash:

$ OS=$(uname -s)
$ [[ ${OS:0:2} = Li ]] && echo "we are running Linux"
we are running Linux

Re: shell script - how hard can it be

Adam Noble — Fri, 09 Feb 2007 07:38:56 GMT

thanks it clearly wasn't as straight forward I was using ksh and your solution worked. Thanks to you both

Re: shell script - how hard can it be

Dennis Handly — Fri, 09 Feb 2007 15:37:21 GMT

You really want to use pattern matching:
if [[ "$revision" = HP* ]]; then

As in Ralph's case, you need [[ ]]. Don't quote the HP*.