Question

Have noticed this a fewtimes when I’m piping something into sed which does not contain any newlines, sed does not execute.

Example, a stream contains some text (without any newline)

foo

The command:

$echo -n "foo" | sed 's/foo/bar/'

Outputs nothing.

Whereas if I add a newline character to the end of the stream, The command above will output the expected replacement:

$echo "foo" | sed 's/foo/bar/'
bar

I’ve found a lot of situations where I don’t have, and don’t really want a newline character in my stream, but I still want to run a sed replacement.

Any ideas how this can be done would be appreciated.

Answer 1

What environment are you in? What sed are you using?

Because here, I’ve got a better sed:

$ echo -n foo | sed 's/foo/bar/'
bar$ 
$ echo -n foo > test.txt
$ hexdump -C test.txt
00000000  66 6f 6f                                          |foo|
00000003
$ cat test.txt | sed 's/foo/bar/'
bar$ cat test.txt | sed 's/foo/bar/' | hexdump -C
00000000  62 61 72                                          |bar|
00000003
$ sed --version
GNU sed version 4.2.1
Copyright (C) 2009 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE,
to the extent permitted by law.

GNU sed home page: <http://www.gnu.org/software/sed/>.
General help using GNU software: <http://www.gnu.org/gethelp/>.
E-mail bug reports to: <[e-mail]>.
Be sure to include the word ``sed'' somewhere in the ``Subject:'' field.

Note that one way to get a better sed is to type it as perl -pe, as in:

$ cat test.txt | perl -pe 's/foo/bar/' | hexdump -C
00000000  62 61 72                                          |bar|
00000003