awk & variable...

DoME69 · 10-03-2008, 12:23 PM

how can i use variable at awk?

i try this..

set go = goooooo
awk '{print "aaa", $1, $go}' file1

but it doesn't work.

David1357 · 10-03-2008, 02:15 PM

Quote:

Originally Posted by DoME69

Code:

set go = goooooo
awk '{print "aaa", $1, $go}' file1

The single quotes surrounding your awk expression prevent it from accessing anything but its internal parameter variables (e.g. $1). You can just rewrite the awk line as

Code:

set go = goooooo
awk '{print "aaa", $1, $2}' file1 $go

colucix · 10-03-2008, 03:20 PM

Quote:

Originally Posted by David1357

Code:

set go = goooooo
awk '{print "aaa", $1, $2}' file1 $go

Unless I'm totally drunk, this should look for a file named "goooooo".

I'd use the -v option, instead:

Code:

awk -v go=$go '{print "aaa", $1, go}' file1

or eventually shell variable substitution through quoting:

Code:

awk '{print "aaa", $1, "'"$go"'"}' file1

but this is more difficult to deal with.

DoME69 · 10-03-2008, 05:49 PM

Quote:

Originally Posted by colucix

Unless I'm totally drunk, this should look for a file named "goooooo".

I'd use the -v option, instead:

Code:

awk -v go=$go '{print "aaa", $1, go}' file1

or eventually shell variable substitution through quoting:

Code:

awk '{print "aaa", $1, "'"$go"'"}' file1

but this is more difficult to deal with.

Thanks a lot.

David1357 · 10-10-2008, 02:47 AM

Quote:

Originally Posted by colucix

Unless I'm totally drunk, this should look for a file named "goooooo".

You are correct. My apologies. When I re-read my original answer I wondered what I was thinking. Thanks for picking up the ball I dropped.

jan61 · 10-12-2008, 08:44 AM

Moin,

another way to do it:

Code:

awk ' ...' go=$go file

Jan

colucix · 10-12-2008, 09:38 AM

Well, the difference between the two methods is that using the -v option the variable is assigned at the very beginning of the awk script, even before the execution of the BEGIN block (if any). The method suggested by jan61 is useful when you have to parse multiple files and use different values of the variable. The variable is assigned depending on its position between the input files, e.g.

Code:

awk 'some_awk_code_here' go=gooooo file1 go=staaaay file2

in this example the variable go will have the value "gooooo" before processing file1 and the value "staaaay" before processing file2.

jan61 · 10-13-2008, 04:32 PM

Moin,

Quote:

Originally Posted by colucix

...

Code:

awk 'some_awk_code_here' go=gooooo file1 go=staaaay file2

in this example the variable go will have the value "gooooo" before processing file1 and the value "staaaay" before processing file2.

that's interesting. I never used it this way and didn't know about the difference. Thanks for the explanation.

Jan

robel · 10-13-2008, 04:44 PM

Quote:

Originally Posted by DoME69

how can i use variable at awk?

i try this..

set go = goooooo
awk '{print "aaa", $1, $go}' file1

but it doesn't work.

Are you trying to access environment variables?

You can access environment variables via the built-in variable ENVIRON

Example:

awk 'BEGIN{ print ENVIRON["TERM"] }'

It would print xterm on my computer.