Question

Given this data

34 foo 34 bar 34 qux 62 foo1 62 qux 78 qux  

I want to replace the string at 2nd column into ” if it is ‘qux’. Resulting:

34 foo 34 bar 34  62 foo1 62  78   

How do you do that with sed? In particular the data is very big with ~10^7 lines

Answer 1

I wouldn’t actually do it with sed since that’s not the best tool for the job. The awk tool is my tool of choice whenever somebody mentions columns.

cat file | awk '$2 == 'qux' { print $1 } $2 != 'qux' { print $0 }' 

or the simplest form:

cat file | awk '{ if ($2 == 'qux') {$2 = ''}; print }' 

If you must use sed:

cat file | sed 's/  *qux *$//' 

making sure that you use the correct white space (the above uses only spaces).