simple shell script

sharpie · 06-02-2004, 02:11 AM

I have 8 tar.gz files that all have the same name, apart from 1 number, obviously going from 1 to 8. Here is the shell script I created, the first tar.gz filename is X11R6.7.0-src1.tar.gz:

Code:

#!/bin/bash

num=1
while [ $num -lt 8 ]; do
	tar -xzvf X11R6.7.0-src$num.tar.gz
	$num = $num + 1
done

It starts to extract and uncompress the 1st one, but never gets to the second one - it just keeps looping on the first one. It seems as though it's ignoring the $num = $num + 1 statement and is just looping the same tar command. What am I doing wrong?

Kumar · 06-02-2004, 02:55 AM

Hi,
change
$num = $num + 1
to
let num=$num+1
and it should work.

seeLnd · 06-02-2004, 03:21 AM

or: num=`expr $num + 1`

mfeat · 06-02-2004, 09:30 AM

while we're seeing how many different ways there are to skin a cat, here's another:

((num=num+1))

seeLnd · 06-02-2004, 09:51 AM

mfeat:

Can you explain this expression ----> ((num=num+1))
I cannot understand the syntax.

thanks

jlliagre · 06-02-2004, 10:39 AM

a longer way to express: ((num++)) ...

mfeat · 06-02-2004, 01:16 PM

"a longer way to express: ((num++))"

cool! i learn something new everyday on this board! i think that sytax is as terse as it gets

mfeat · 06-02-2004, 01:20 PM

"Can you explain this expression ----> ((num=num+1))
I cannot understand the syntax."

seeLND:

from the bash man page:

((expression))
The expression is evaluated according to the rules described
below under ARITHMETIC EVALUATION. If the value of the expres-
sion is non-zero, the return status is 0; otherwise the return
status is 1. This is exactly equivalent to let "expression".

jspenguin · 06-02-2004, 08:42 PM

How about

Code:

for num in `seq 1 8`; do
	tar -xzvf X11R6.7.0-src$num.tar.gz
done

seeLnd · 06-02-2004, 11:47 PM

everyone is perfect