Handy gsub examples:
Removing the trailing % in the 5th field.
# echo "1 2 3 4 85%" | awk '/%/{gsub( /%/," ",$5); print}'
1 2 3 4 85
- /%/ operate only on lines with a %
(this means empty lines are skipped) - gsub(a,b,c) match the regular expression a, replace it with b,
and do all this with the contents of c - print print the contents of the entire line
# echo "1 2 3 4 85%" | awk '/%/{gsub( /%/," ",$5); print $5}'
85
- /%/ operate only on lines with a %
(this means empty lines are skipped) - gsub(a,b,c) match the regular expression a, replace it with b,
and do all this with the contents of c - print $5 print the contents of the 5th field
# echo "1 2 3 4 85%" | awk '/%/{gsub( /%/," ",$5); print $5","$2}'
85 ,2
- /%/ operate only on lines with a %
(this means empty lines are skipped) - gsub(a,b,c) match the regular expression a, replace it with b,
and do all this with the contents of c - print $5″,”$2 print the contents of field 5, a comma, then field 2
# echo "1:2:3:4:85%" | awk -F: '/%/{gsub( /%/," ",$5); print$5","$2}'
85 ,2
- -F: use : as field separator
- /%/ operate only on lines with a %
(this means empty lines are skipped) - gsub(a,b,c) match the regular expression a, replace it with b,
and do all this with the contents of c - print$5″,”$2 print the contents of field 5, a comma, then field 2
Need to remove white spaces?
# echo "1: 2 :3:4:5:6" | awk -F: '{print $2}'
2
# echo "1: 2 :3:4:5:6" | awk 'BEGIN{FS=OFS=":"}{gsub(/^[ \t]+/,"",$2);gsub(/[ \t]+$/,"",$2)}1'
1:2:3:4:5:6
- BEGIN{FS=OFS=”:”} – use : as field separator
- gsub(/^[ \t]+/,””,$2); – starting at the beginning (^) replace all (+ = zero or more, greedy)
consecutive tabs and spaces with an empty string - gsub(/[ \t]+$/,””,$2)} – do the same, but now for all space up to the end of string ($)
1 – =”true”. Shorthand for “use default action”, which is print $0
– that is, print the entire (modified) line
# echo "1: 2 :3:4:5:6" | awk 'BEGIN{FS=OFS=":"}{gsub(/^[ \t]+/,"",$2);gsub(/[ \t]+$/,"",$2); print $2}'
2
Same as above but print specific fields.
- ;print $2 print the 2nd field. Notice the print is before the curly bracket } and followed by a semi-colon :
This post was based on the following stockoverflow.com question:
http://stackoverflow.com/questions/20600982/remove-leading-and-trailing-space-in-field-in-awk