I need to replace ^ A, ^ B in a file, the following command is useless: S / ^ A /
To get a character ^A , press CTRL-V CTRL -A
^A
If you configured the insert action with CTRL- V(usually on Windows), you can use CTRL- Qinstead.
You need to escape the ^ with \, i.e. s/\^A/^B/ ... ^ stands for "start of line" in a regular expression. In the replacement text, escaping is optional, but possible.
s/\^A/^B/