how to remove the first two columns in a file using shell (awk, sed, whatever)

Question

I have a file with many lines in each line there are many columns(fields) separated by blank " " the numbers of columns in each line are different I want to remove the first two columns how to?

Answer 1

You can do it with cut:

cut -d " " -f 3- input_filename > output_filename

Explanation:

• cut: invoke the cut command
• -d " ": use a single space as the delimiter (cut uses TAB by default)
• -f: specify fields to keep
• 3-: all the fields starting with field 3
• input_filename: use this file as the input
• > output_filename: write the output to this file.

Alternatively, you can do it with awk:

awk '{$1=""; $2=""; sub("  ", " "); print}' input_filename > output_filename

Explanation:

• awk: invoke the awk command
• $1=""; $2="";: set field 1 and 2 to the empty string
• sub(...);: clean up the output fields because fields 1 & 2 will still be delimited by " "
• print: print the modified line
• input_filename > output_filename: same as above.