sed command find and replace in file and overwrite

Question

I would like to run a find and replace on an HTML file through the command line.

My command looks something like this:

sed -e s/STRING_TO_REPLACE/STRING_TO_REPLACE_IT/g index.html > index.html

When I run this and look at the file afterward, it is empty. It deleted the contents of my file.

When I run this after restoring the file again:

sed -e s/STRING_TO_REPLACE/STRING_TO_REPLACE_IT/g index.html

The stdout is the contents of the file, and the find and replace has been executed.

Why is this happening?

Answer 1

use sed's -i option, e.g.

sed -i bak -e s/STRING_TO_REPLACE/REPLACE_WITH/g index.html

Answer 2

sed -i.bak "s#https.*\.com#$pub_url#g" MyHTMLFile.html

If you have a link to be added, try this. Search for the URL as above (starting with https and ending with.com here) and replace it with a URL string. I have used a variable $pub_url here. s here means search and g means global replacement.

It works !

Answer 3

And the ed answer:

printf "%s\n" '1,$s/STRING_TO_REPLACE/STRING_TO_REPLACE_IT/g' w q | ed index.html

To reiterate what codaddict answered, the shell handles the redirection first, wiping out the "input.html" file, and then the shell invokes the "sed" command passing it a now empty file.

Answer 4

sed -i 's/STRING_TO_REPLACE/STRING_TO_REPLACE_IT/g' index.html

This does a global in-place substitution on the file index.html. Quoting the string prevents problems with whitespace in the query and replacement.

Answer 5

The problem with the command

sed 'code' file > file

is that file is truncated by the shell before sed actually gets to process it. As a result, you get an empty file.

The sed way to do this is to use -i to edit in place, as other answers suggested. However, this is not always what you want. -i will create a temporary file that will then be used to replace the original file. This is problematic if your original file was a link (the link will be replaced by a regular file). If you need to preserve links, you can use a temporary variable to store the output of sed before writing it back to the file, like this:

tmp=$(sed 'code' file); echo -n "$tmp" > file

Better yet, use printf instead of echo since echo is likely to process \\ as \ in some shells (e.g. dash):

tmp=$(sed 'code' file); printf "%s" "$tmp" > file

Answer 6

I was searching for the option where I can define the line range and found the answer. For example I want to change host1 to host2 from line 36-57.

sed '36,57 s/host1/host2/g' myfile.txt > myfile1.txt

You can use gi option as well to ignore the character case.

sed '30,40 s/version/story/gi' myfile.txt > myfile1.txt