用awk附加到文件的某些行，不匹配的行保持不变

Question

given file test and its content:

bcd://dfl
sf

I would like to append extra information to the line having certain content (starting with bcd ) While the following script works

awk '/bcd*/ {print $0", extra information"} ' test > test.old && mv test.old test

it removes the non matching lines. ( sf )

Is it possible to preserve them in the output file?

Answer 1

As discussed over in the comments appending a {..}1 at the end will solve your problem,

awk '/^bcd/ {print $0", extra information"; next} 1' file

because the /<pattern>/{<action>} is applied to the lines only matching the <pattern> , the other lines are just printed as-is, {..}1 is a always-true-no-matter-what condition to print lines.

Answer 2

awk '/^bcd/ {$0 = $0 ", extra information"} 1' test