issues with sed on Mountain Lion

Question

I am trying to delete a line on a file that looks like this:

test 1800 IN CNAME mydomain.com.

I am using sed on Mountain Lion and I am trying the following but I keep getting no errors, however the line is not deleted.

sed -i -e '/$regex/d' $file

or

sed -i "" -e '/$regex/d' $file

Where the $regex is the expression containing the line mention above and the $file is the name of the file where the line is.

Any help Will be appreciate it.

Answer 1

This is a near duplicate of Sed command find and replace in file ... , and the most portable answer is the same as there:

sed -e '/$regex/d' $file >$file.tmp && mv $file.tmp $file

...for the reasons, and with the advantages, given there. When you're concerned about portability, the POSIX spec is a great resource, since it describes a common subset of unix commands, which is often frustratingly restricted, but which is pretty reliably present in all the unixes one is likely to come across.

Answer 2

Mountain Lion (v10.8.2) works just fine with sed -i "" -e '/$regex/d' $file

[Mar 12 17:22] [jnovack@growlithe ~]$ more test.php
<?php
echo "Test php echo 1";
echo "Test echo 2";
?>
[Mar 12 17:22] [jnovack@growlithe ~]$ sed -i "" -e "/php/d" test.php
[Mar 12 17:22] [jnovack@growlithe ~]$ more test.php
echo "Test echo 2";
?>

Answer 3

The most likely problem, it seems to me, is that you have a shell variable $regex which contains the pattern to be searched for and deleted, but your single quotes prevent the shell expanding it. You likely need to use:

sed -i .bak -e "/$regex/d" $file

(BSD sed on Lion and Mountain Lion supports the -i option. The manual page recommends against a zero-length back-up extension.)

-i extension

Edit files in-place, saving backups with the specified extension. If a zero-length extension is given, no backup will be saved. It is not recommended to give a zero-length extension when in-place editing files, as you risk corruption or partial content in situations where disk space is exhausted, etc.