Text Processing – Print Only the Last Three Columns from a File

With GNU grep which supports -o option to print only matched string, each on its own line

$ grep -oE '\b35=[^,]+' ip.csv 
35=A
35=BCD
35=EF
35=G

• \b is word boundary, so that 900035 won't match
• [^,]+ to match one or more non, characters
• assumes the values do not contain ,

With awk

$ awk -F, '{ for(i=1;i<=NF;i++){if($i~/^35=/) print $i} }' ip.csv 
35=A
35=BCD
35=EF
35=G

• -F, set , as input field separator
• for(i=1;i<=NF;i++) iterate over all fields
• if($i~/^35=/) if field starts with 35=
  • print $i print that field

Similar with perl

perl -F, -lane 'foreach (@F){print if /^35=/}' ip.csv 

awk -v n=4 '{ for (i=n; i<=NF; i++) printf "%s%s", $i, (i<NF ? OFS : ORS)}' input

This will take n as the value of n and loop through that number through the last field NF, for each iteration it will print the current value, if that is not the last value in the line it will print OFS after it (space), if it is the last value on the line it will print ORS after it (newline).

$ echo 'vddp vddpi vss cb0 cb1 cb2 cb3 ct0 ct1 ct2 ct3' |
> awk -v n=4 '{ for (i=n; i<=NF; i++) printf "%s%s", $i, (i<NF ? OFS : ORS)}'
cb0 cb1 cb2 cb3 ct0 ct1 ct2 ct3