Help with shell script

Gins · 08-27-2006, 07:44 AM

#!/bin/sh
set -e
echo "The amount of commandline args is $#"
echo "They are \"$@\""
n=0; for arg in $@;

do

if

[ "$arg" = "$LOGNAME" ];

then

echo "Number $n is logname"

fi

let n=${n}+1; shift $n;

done

exit 0
-----------------------------------

I saved the above program as 'argument2'.

When I write 'env' at the commoand line, it says 'LOGNAME=nissanka' and a lot of other details.

I ran the program by giving 3 arguments. They are 'nissanka' , 'df' and 'du'.

[nissanka@c83-250-110-112 ~]$ ./argument2 nissanka df du
The amount of commandline args is 3
They are "nissanka df du"
Number 0 is logname
[nissanka@c83-250-110-112 ~]$

I have a few questions on this.
1.Why did I get number 0 logname?

2. What is this line doing ---> let n=${n}+1; shift $n;

I would like to hear from you all.

Gins · 08-27-2006, 09:43 AM

I urge someone to provide me a with a reply. I am a learner too. When I find time, I look at scripting language by running a small program or two.

unSpawn · 08-28-2006, 10:51 AM

Why did I get number 0 logname?
Because of:

Code:

# Initialise "counter"
n=0
# Take all commandline arguments and loop over them
for arg in nissanka df du;
 # If the argument we're inspecting matches the logname
 # of the currently logged in user, echo some text
 if [ nissanka = nissanka ]; then
  echo "Number 0 is logname"
 fi

It's easier to see values get filled in if you run the script as: "sh -x argument2 nissanka df du".

What is this line doing ---> let n=${n}+
"let" ("help let") does arithmetic expressions, in this case it takes the value of the counter and increments it by one. Another notation could be ((n++)) or n=$[${n}+1]

; shift $n;
When executing a Bash shell script the scriptname occupies variable "$0". Commandline arguments take up positions 1 through * where 1 through 9 are available immediately. If you would like to see the next one you use "shift" ("help shift") "to, ahhh, shift focus.

I urge someone to provide me a with a reply.
...and that's the reason we had your posts moved to your own brand new thread. If we didn't people would think you just replied to the OP (which you didnt, which in the worse cases is called thread hijacking) and would easily miss your questions. So: your questions -> your own thread. And you best wait 24 hours before asking for a reply. Zero-reply threads get bumped automagically so you only have to work on your patience.

Gins · 08-28-2006, 12:26 PM

unSpawn, it was an excellent lengthy reply. Thank you very much.

As a moderator you could replace or remove my threads. I respect to your inalienable rights.