awk substitution using gsub

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 :