Problem with while loop

orbitalen · 09-03-2009, 03:10 AM

Hello everyone! I'm having a problem with this simple script...

ls -la /|awk '{print $8}'>list
while read line
do
if "$line"="boot"
then
echo "$line"
fi
done < list;

Can anyone help me? When I run it I get:

bash: =boot: command not found
bash: .=boot: command not found
bash: ..=boot: command not found
.
.
.
and all the way down untill the end ot the file...

Anyone!?

colucix · 09-03-2009, 03:12 AM

Code:

if [ "$line" = "boot" ]

you have to use square brackets to perform a numeric or string comparison. Without them the expression is interpreted as a command, hence the command not found error. Indeed you can also test for commands using if/then without brackets: it will evaluate the exit status of the command (success or failure), but this is another story.

JulianTosh · 09-03-2009, 03:15 AM

if [ "$line"="boot" ]

orbitalen · 09-03-2009, 03:15 AM

Ok, the error is gone now, but the output is the content of the file (the whole content), not just boot...

colucix · 09-03-2009, 03:18 AM

Quote:

Originally Posted by orbitalen

Ok, the error is gone now, but the output is the content of the file (the whole content), not just boot...

Given the lines of code you have posted, that's not possible. Maybe the entire content of the file is displayed from a command you didn't show us. What is the actual code of your script?

orbitalen · 09-03-2009, 03:21 AM

Well, that's it... I run the ls -la .... command in the command line to generate the file and then run:

# while read line; do if [ "$line"="boot" ]; then echo "$line"; fi done < list

And I get the content of the whole file...

The idea is to use this code (of course with lots of changes) in another script, but the mistake is the same here and there...

JulianTosh · 09-03-2009, 03:22 AM

I think that might actually need to be

Code:

if [ "$line" == "boot" ]

I dont get any output with that (coz there's no 'boot' in the line)

orbitalen · 09-03-2009, 03:24 AM

Quote:

Originally Posted by Admiral Beotch

I think that might actually need to be

Code:

if [ "$line" == "boot" ]

I dont get any output with that (coz there's no 'boot' in the line)

OK... that worked! :P Thanks, guys!! Help appreciated!

colucix · 09-03-2009, 03:31 AM

Quote:

Originally Posted by Admiral Beotch

I think that might actually need to be

Code:

if [ "$line" == "boot" ]

I dont get any output with that (coz there's no 'boot' in the line)

Not really true, indeed. In bash you can use either = and == for string comparison. The problem was that the OP didn't put spaces around the = sign. This resulted in a whole and unique string which is always evaluated as true.

JulianTosh · 09-03-2009, 03:37 AM

Yeah I was kinda confused about that cause I just read the man page and it said = is the same as ==..

Persnickety. Thanks for that.