Insert some text after Nth matching pattern using sed

问题

How can I do so? I have multiple e.g. foobar patterns in my file, how can I add after e.g. the 4th one some_text?

回答1:

Does the following work for you?

sed ':a;$!{N;ba};s/\(foobar\)/\1\nsome_text/4' inputfile

For the input:

$ cat inputfile
line
foobar
foobar
foobar
line
foobar
line
foobar
line
foobar
line

This would generate

$ sed ':a;$!{N;ba};s/\(foobar\)/\1\nsome_text/4' inputfile
line
foobar
foobar
foobar
line
foobar
some_text
line
foobar
line
foobar
line

Use -e on FreeBSD:

sed -e :a -e '$!N' -e '$!ba' -e 's/\(foobar\)/\1\nsome_text/4' inputfile

回答2:

an awk version:

 awk '/foo/{x++} x==4{sub(/foo/,"&some_text")}1' file

example:

kent$  cat file
foo
foo
trash
foo
trash
foo
foo
foo

kent$  awk '/foo/{x++} x==4{sub(/foo/,"&some_text")}1' file
foo
foo
trash
foo
trash
foosome_text
foo
foo

来源：https://stackoverflow.com/questions/17465356/insert-some-text-after-nth-matching-pattern-using-sed