Search and replace with sed when dots and undersco

Question

How do I replace foo. with foo_ with sed simply running

sed 's/foo./foo_/g' file.php

doesn't work. Thanks!

Answer 1

Interestingly, if you want to search for and replace just the dot, you have to put the dot in a character set. Escaping just the dot alone in a sed command for some reason doesn't work. The dot is still expanded to a single character wild card.

$ bash --version  # Ubuntu Lucid (10.04)

GNU bash, version 4.1.5(1)-release (x86_64-pc-linux-gnu)

$ echo aa.bb.cc | sed s/\./-/g  # replaces all characters with dash

'--------'

$ echo aa.bb.cc | sed s/[.]/-/g  # replaces the dots with a dash

aa-bb-cc

With the addition of leading characters in the search, the escape works.

$ echo foo. | sed s/foo\./foo_/g  # works

foo_

Putting the dot in a character set of course also works.

$ echo foo. | sed s/foo[.]/foo_/g  # also works

foo_

-- Paul

Answer 2

For myself, sed 's/foo\./foo_/g' is working. But you can also try:

sed -e 's/foo\./foo_/g'

and

sed -e "s/foo\\./foo_/g"

and

sed 's/foo[.]/foo_/g'

Answer 3

Escape the dot with a \

sed 's/foo\./foo_/g' file.php

If you find the combination of / and \ confusing you can use another 'separator' character

sed 's#foo\.#foo_#g

The 2nd character after the s can be anything and sed will use that character as a separator.

Answer 4

You need to escape the dot - an unescaped dot will match any character after foo.

sed 's/foo\./foo_/g'

Answer 5

Escape the .:

sed 's/foo\./foo_/g' file.php

Example:

~$ cat test.txt 
foo.bar
~$ sed 's/foo\./foo_/g' test.txt 
foo_bar