linux - Regex replace on specific column with SED/AWK -

i have data looks (tab delimited):

organ k     clustno analysis ln    k200  c12     gene ontology ln    k200  c116    gene ontology cn    k200  c2      gene ontology 

what want remove c every row on 3rd column, except header row:

organ k     clustno analysis ln    k200  12      gene ontology ln    k200  116     gene ontology cn    k200  2       gene ontology 

this won't because affect other columns , header row:

sed 's/c//' 

what's right way it?

using awk

awk tool this:

$ awk -f'\t' -v ofs='\t' 'nr>=2{sub(/^c/, "", $3)} 1' file organ   k       clustno analysis ln      k200    12      gene ontology ln      k200    116     gene ontology cn      k200    2       gene ontology 

how works

• -f'\t'

  use tab field delimiter on input.

• -v ofs='\t'

  use tab field delimiter on output

• nr>=2 {sub(/^c/, "", $3)}

  remove initial c field 3 lines after first line.

• 1

  this awk's cryptic shorthand print-the-line.

using sed

$ sed -r '2,$ s/(([^\t]+\t+){2})c/\1/' file organ   k       clustno analysis ln      k200    12      gene ontology ln      k200    116     gene ontology cn      k200    2       gene ontology 

• -r

  use extended regular expressions. (on mac osx or other bsd platform, use -e instead.)

• 2,$ s/(([^\t]+\t){2})c/\1/

  this substitution applied lines 2 end of file.

  (([^\t]+\t){2}) matches first 2 tab-separated columns. assumes 1 tab separates each column. because regex enclosed in parens, matches available later \1.

  c match c.

  \1 replaces matched text first 2 columns, not c..