awk in script

Jurrian · 10-30-2008, 02:50 AM

Hi all,

I want to split the result of a command to only use the first word.
Searching on internet resulted in awk, so I use it as following:

Code:

awk '{print $1}' input.txt

this works fine when I use commandline.

However, when I put it inside a small script:

Code:

du $1 > currentdiroutputtemp.txt
FILESIZE="awk '{print $1}' currentdirouttemp.txt"
echo $FILESIZE
$FILESIZE

it fails to succesfully parse the $1, as it will use the $1 from executing the script. Is there anyway I can prevent this?

Thanx in advance,

Jurrian

maradnus · 10-30-2008, 03:33 AM

Hi

There are some simple mistakes .......
look at the filename currentdiroutputtemp..
Use backquote instead of " to capture the output of a command

have a good day

Code:

 

du $1 > currentdiroutputtemp.txt
FILESIZE=`awk '{print $1}' currentdiroutputtemp.txt`
echo $FILESIZE

Jurrian · 10-30-2008, 03:43 AM

Hi,

Thanx for answer, but it is not completely working yet. This is my script:

Code:

touch currentdirouttemp.txt
touch finaloutput.txt
echo "du $1 > currentdiroutputtemp.txt"
du $1 > currentdiroutputtemp.txt
FILESIZE=`awk '{print $1}' currentdirouttemp.txt`
echo $FILESIZE
$FILESIZE > finaloutput.txt
rm currentdirouttemp.txt

this is output:
[jurrian@Jurrian test]$ ./size.sh size.sh
du size.sh > currentdiroutputtemp.txt

[jurrian@Jurrian test]$

for some reason the FILESIZE variable isn't parsed correctly, what mistake do I make?

H_TeXMeX_H · 10-30-2008, 03:43 AM

I don't get what is this supposed to do:

Code:

echo "du $1 > currentdiroutputtemp.txt"

Jurrian · 10-30-2008, 03:46 AM

When I change the backquotes with $() I still get the same error that my FILESIZE is empty..

maradnus · 10-30-2008, 03:49 AM

The problem is in the filename: currentdirouttemp.txt

FILESIZE=`awk '{print $1}' currentdirouttemp.txt`

where put is missing.

and

echo $FILESIZE
$FILESIZE > finaloutput.txt

instead of that

echo $FILESIZE > finaloutput.txt

good

Jurrian · 10-30-2008, 03:53 AM

thanks for your help. What is exact the difference between the backquotes and $()? Why should I try to avoid this, or is this nonsense?

Jurrian · 10-30-2008, 03:54 AM

Quote:

Originally Posted by H_TeXMeX_H

I don't get what is this supposed to do:

Code:

echo "du $1 > currentdiroutputtemp.txt"

Since I am testing the script, I always like to know what it did, so I echo it to the command line, to be sure no type errors or something exist.

maradnus · 10-30-2008, 03:58 AM

hi

both $() and `` are used for the same purpose.

thanks

Jurrian · 10-30-2008, 04:16 AM

ok, thank you for your help

jschiwal · 10-30-2008, 04:19 AM

Why not simply pipe the output of du into awk?

Code:

du "${1:-.}" | awk '{print $1}'

Jurrian · 10-30-2008, 05:06 AM

because I didn't know it was possible

could you explain the part "${1:-.}" to me? What if I just want to add a path instead of letting my script be parsed when an argument is passed,
would that become du /path | awk '{print $1}' ?

jschiwal · 10-30-2008, 05:28 AM

The "${1:-.}" part will either use the first argument when calling the script; or if there is no argument, use "." which is the current directory instead. The "." becomes a default argument.

chrism01 · 10-30-2008, 07:09 PM

Incidentally, the 'touch' cmds are redundant.