replacing text in files

Laurent Perrinet

using sed

The UNIX command sed is useful to find and replace text in single or multiple files. This page lists some common commands in using sed to improve editing code.
To replace foo with foo_bar in a single file:
```
sed -i 's/foo/foo_bar/g' my_script.py
```
- -i = edit the file "in-place": sed will directly modify the file if it finds anything to replace
- s = substitute the following text
- foo = the text string to be substituted
- foo_bar = the replacement string
- g = global, match all occurrences in the line
To replace foo with foo_bar in multiple files:
```
sed -i 's/foo/foo_bar/g'  *.py
```
Consult the manual pages of the operating system that you use: man sed

in the particular case of changing a scaling parameter in a set of experiment files:

sed -i 's/size = 6/size = 7/g'  experiment*.py
sed -i 's/size = 7/size = 6/g'  experiment*.py

on the current buffer, with confirmation
```
:%s/old_text/new_text/cg
```
on the current buffer
```
:%s/old_text/new_text/g
```
to get help
```
:help substitute
```
one could pass the required files to 'args' and apply whatever command to all these files using the command 'argdo'. First I will apply the substitute 's' command and then 'update' which will only save the modified files.
```
:args *.py
:argdo :%s/old_text/new_text/g | update
```