Sed — Stream Editor

Print Lines From a File

Print entire file:

$ cat file.txt (1)
$ sed '' file.tx (2)
$ sed -n p file.txt (3)
$ sed -n '1,$ p' file.txt (3)

  1. Yeah, we could use cat.

  2. Or use an empty command, which by default (without -n) just outputs the content of the pattern space.

  3. Or using -n to avoid auto-printing of the pattern space and explicitly using p command to print, which prints all the lines if no address is used.

  4. Doing everything explicitly.

GNU sed -i option

$ sed -i 's/^  /\t/' < Makefile
sed: no input files

Of course, the -i option takes a file, not STDIN. We got STDIN instead of the Makefile because we used redirection.