CODEWITHSUNDEEP
regexunixawk
Andrew Nguyen
Andrew Nguyen

Reputation: 701

Awk: Splitting on 2 or more spaces only

I'm trying to reformat the output of the last command e.g. last -adn 10 | head -n -2 | awk -F' {2,}' '{ print "USER:",$1,"IP:",$5 }'. 

>> last -adn 10 | head -n -2
root     pts/0        Tue Jul 10 13:51   still logged in    10.102.11.34
reboot   system boot  Fri Jun 22 09:37         (18+04:19)   0.0.0.0

I would like my output to be something like:

>>last -adn 10 | head -n -2 | awk -F' {2,}' '{ print "USER:",$1,"IP:",$5 }'
USER: root IP: 10.102.11.34 TIME: Tue Jul 10 13:51

I've tried every method described here, and I can't figure out why this is not working for me. When executing that command, it simply stores the whole line in $1, and the others are blank.

Upvotes: 12

Views: 8860

Answers (2)

Levon
Levon

Reputation: 143027

UPDATE based on @WilliamPursell comment/suggestion:

Instead of this:

awk -F' {2,}' '{ print "USER:",$1,"IP:",$5 }'

Try this:

awk 'BEGIN{FS="   *"}{ print "USER:",$1,"IP:",$5 }'

seems to be working for me and fixes the shortcoming of my previous solution using 'BEGIN{FS=" "}... which only split on exactly 2 spaces.

Note: FS is set to 3 spaces and an *, meaning the last space can occur zero or more times.

Upvotes: 7

Todd A. Jacobs
Todd A. Jacobs

Reputation: 84343

By default, gawk does not enable interval expressions. You can enable them with the --re-interval flag. Other versions of awk may or may not support them at all.

If you can't enable the flag, you can use a more explicit match. For example:

$ echo 'foo  bar baz' |
    awk -F'[[:space:]][[:space:]][[:space:]]*' '{print $2}'
bar baz

Upvotes: 4

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