How can I replace all instances of a specified string in a text file with another string?

Question

I have a file a.txt. I would like to replace all instances of "1.6" with "1.5" in that file, overwriting the original file.

Answer 1

Using the command line :

sed -i .bak -e 's/1\.5/1.6/g' /path/to/file

This command replace in the file, the orginal file is saved as /path/to/file.bak

Answer 2

You can use sed for that:

sed 's/1\.5/1\.6/g' /path/to/file | tee output

also if you are inside an editor like vim, you can do that :

vim /path/to/file
:%s/1\.5/1\.6/g 

In emacs :

emacs /path/to/file
M-x replace-string