awk or sed: Best way to grab [this text]

Question

I'm trying to parse various info from log files, some of which is placed within square brackets. For example:

Tue, 06 Nov 2007 10:04:11 INFO     processor:receive: [someuserid], [somemessage]  msgtype=[T]

What's an elegant way to grab 'someuserid' from these lines, using sed, awk, or other unix utility?

Answer 1

cut
use it like this: cut -f2 -d[ | cut -f1 -d]

bart@hal9k:~> YOURTEXT="Tue, 06 Nov 2007 10:04:11 INFO     processor:receive: [someuserid], [somemessage]  msgtype=[T]"
bart@hal9k:~> SOMEID=`echo $YOURTEXT | cut -f2 -d[ | cut -f1 -d]`
bart@hal9k:~> echo $SOMEID
someuserid

Answer 2

If you want to do something with all the bracketed fields, I'd use Perl:

perl -lne '
    my @fields = /\[(.*?)\]/g;
    # do something with @fields, like:
    print join(":", @fields);
' logfile ...

Answer 3

using bash shell

while read -r line
do
   case "$line" in
        *processor*receive* ) 
            t=${line#*[}
            echo ${t%%]*}
            ;;
   esac
done < "file"

Answer 4

sed -n '/INFO/{s/.[^[]*\[//;s/\].*//p}' file

Answer 5

Using AWK:

cat file | awk -F[\]\[] '{print $2}'

I have found that multiple delimiters do not work in some older versions of AWK. If it doesn't, you can use two awks:

cat file | awk -F[ '{print $2}' | awk -F] '{print $1}'