Sed -e 'Unterminated 's' command

Question

Im trying to escape all the backslashes from some text generated by figlet. Here is what I have so far.

figlet -f $font -t "Foo Bar" | sed -e "s|\\|\\\\|g"

This doesn't work for some reason, but this does.

figlet -f $font -t "Foo Bar" | sed -e "s| |X|g"

Am I misunderstanding how sed works here? I couldn't find similar posts about this either.

Answer 1

The double quotes do not protect the backslashes that are inside the sed -e "s|\\|\\\\|g" from the shell's attempts to parse them. If you use a simpler example you can see this a bit more easily:

$ echo 'blah\blah'| sed -e "s|\\|blah|g"
sed: -e expression #1, char 10: unterminated `s' command

$ echo 'blah\blah'| sed -e 's|\\|blah|g'
blahblahblah

If you want to use the first form of your sed you need to switch it to single quotes instead of double.

$ figlet -t "Foo Bar" | sed -e 's|\\|\\\\|g'
 _____             ____
|  ___|__   ___   | __ )  __ _ _ __
| |_ / _ \\ / _ \\  |  _ \\ / _` | '__|
|  _| (_) | (_) | | |_) | (_| | |
|_|  \\___/ \\___/  |____/ \\__,_|_|

If you have to use double quotes, then you need more backslashes to escape the shell and sed:

$ figlet -t "Foo Bar" | sed -e "s|\\\|\\\\\\\|g"
 _____             ____
|  ___|__   ___   | __ )  __ _ _ __
| |_ / _ \\ / _ \\  |  _ \\ / _` | '__|
|  _| (_) | (_) | | |_) | (_| | |
|_|  \\___/ \\___/  |____/ \\__,_|_|