[SOLVED] in need for an advice regarding awk command

Tux Rules · 10-30-2010, 05:52 AM

I've just discovered this cool nifty and handy command that I think would help me a lot, but something it's not really clear to me though I've read some tutorials about it. I know if you wanna print the info of a column using awk you refer to that column using the dollar sign $, but I didn't get it how you can refer to a row or how can you refer to a certain value that it's situated in a matrix.

For example if I do df -H this pops out in my terminal

Code:

Filesystem            Size  Used Avail Use% Mounted on
/dev/sda10             48G   13G   33G  28% /
tmpfs                1006M   12K 1006M   1% /lib/init/rw
udev                 1001M  288K 1001M   1% /dev
tmpfs                1006M  524K 1006M   1% /dev/shm
/dev/sda6              98G   77G   22G  79% /mnt/WD_1
/dev/sda7              98G   26G   73G  26% /mnt/WD_3
/dev/sda5              98G   53G   45G  55% /mnt/WD_kit
/dev/sda1              76G   45G   31G  60% /mnt/sda1
/dev/sda9              49G   27G   23G  55% /mnt/sda9

If I do df -H|awk '/ / {print $3}' it will show me the used space column

Code:

Used
14G
13k
295k
537k
83G
28G
57G
49G
29G

Ok now how can I make awk so it will diplay only the 26G used space of my sda7 without involving grep command 'cause I know another way it would be something like df -H|grep sda7|awk '/ / {print $3}', but because I need to get these values so I could perform calculations with them inside awk involving grep will only make things harder and awk-ard 8-)

So anybody has any idea how can I refer to a specific value from a matrix like display, using awk ?

Nylex · 10-30-2010, 05:58 AM

awk '/sda7/ {print $3}'

Look at using regular expressions with (g)awk: http://www.gnu.org/manual/gawk/gawk.html#Regexp-Usage

Tux Rules · 10-30-2010, 06:36 AM

Quote:

Originally Posted by Nylex

awk '/sda7/ {print $3}'

Look at using regular expressions with (g)awk: http://www.gnu.org/manual/gawk/gawk.html#Regexp-Usage

thx man I'm new to all the awk-enish and that was pretty handy, 'cause i can see actually awk has grep implementated inside it.

I needed awk to display the used and fre space of my NTFS partitions that are mounted in the /mnt folder. Now I can accomplish that with the command

Code:

df -h|awk '/mnt/ {{used += $3} {free += $4}} END {{print used} {print free}}'

colucix · 10-30-2010, 07:12 AM

Just an aside note: you don't need so many brackets. In order to have multiple statements on the same line, you can separate them by semi-colon:

Code:

awk '/mnt/{used += $3; free += $4} END {print used; print free}'

Apart from various awk tutorials, the best reference is the official documentation, here. Enjoy awk!