topic Re: Korn shell script problem in Operating System - HP-UX

Korn shell script problem

Henry Chua — Wed, 24 Nov 2004 09:39:08 GMT

I can't seems to make this program work. It is suppose to read line by line of file TAR until EOF. something seems to be run with the awk command, I dun seems to know whether to put the ` ' or " . anyone can help?

y=1
x=1
while [ y -ne 0 ]
do
awk "NR==$x" $TAR > $BUF
let "x=x+1"
y=`wc -c $BUF`
done

Re: Korn shell script problem

Jean-Luc Oudart — Wed, 24 Nov 2004 09:43:55 GMT

would that be
while [ $y -ne 0 ]
instead of
while [ y -ne 0 ]

Regards
Jean-Luc

Re: Korn shell script problem

Henry Chua — Wed, 24 Nov 2004 09:48:51 GMT

Thanks Jean,

But is the awk command I issued correct?

thanks!

Re: Korn shell script problem

Sridhar Bhaskarla — Wed, 24 Nov 2004 09:49:53 GMT

Hi Henry,

I don't know what you are trying to do. Why do you want to use a script to read it line by line? Can you do something like

while read line
do
echo $line

done < $TAR

to read line by line?.

If you insist on using the script, then there are couple of issues.

1. while [ y -ne 0 ] should be while [ $y -ne 0 ]. Use [[ and ]] instead.
2. awk "NR==$x" won't work. You can't assing a shell variable inside awk. Do
awk -v x=$x 'NR==x' $TAR > $BUF
No $ for variables inside awk.
3. Try (( x = $x + 1 )) instead of let.

-Sri

Re: Korn shell script problem

Henry Chua — Wed, 24 Nov 2004 09:59:32 GMT

Hi Sri

as advised I used
"awk -v x=$x 'NR==x' $TAR > $BUF"
and it produces

awk: syntax error near line 1
awk: bailing out near line 1

what could be wrong?

thanks!

Re: Korn shell script problem

Sridhar Bhaskarla — Wed, 24 Nov 2004 10:16:56 GMT

It works for me. Try with sh -x <script> and see if you get more information.

$TAR=testfile
$x=2
$awk -v x=$x 'NR==x' $TAR
testline 2

-Sri

Re: Korn shell script problem

MarkSyder — Wed, 24 Nov 2004 10:18:54 GMT

Henry,

When I first started working with unix, one of my colleagues said "A shell script doesn't deserve the name shell script unless it contains at least one awk".

I don't agree with him! Sri's "while read line" suggestion is just as effective as awk and easier to script.

Mark Syder (like the drink but spelt different)

Re: Korn shell script problem

Gregory Fruth — Wed, 24 Nov 2004 15:53:17 GMT

You can indeed use shell variables in
an awk program, but only because the shell
substitutes inside of double quotes:

x=2
awk "NR == $x" some_file

If you use single quotes the shell won't
substitute for $x.

However, I don't understand why you are
doing this in such a roundabout manner.
Replacing your entire program with
"cat $TAR" will also read from TAR until
EOF. What are you trying to accomplish?

Re: Korn shell script problem

Henry Chua — Wed, 24 Nov 2004 18:37:41 GMT

hi Sri,

DOes that mean I can read line 1 of the file this way:
"
TAR = filename
x=1
while read x
do
echo $x

done < $TAR
"
Thanks!

Re: Korn shell script problem

Henry Chua — Wed, 24 Nov 2004 19:51:34 GMT

I got it! thank!!!