Question

I have a plain text document, which I want to compile inside LaTeX. However, sometimes it has the characters, “#”, “$”, “%”, “&”, and “_”. To compile properly in LaTeX, I must first replace these characters with “#”, “\$”, “\%”, “\&”, and “_”. I have used this line in sed:

sed -i 's/\#/\\\#/g' ./file.txt
sed -i 's/\$/\\\$/g' ./file.txt
sed -i 's/\%/\\\%/g' ./file.txt
sed -i 's/\&/\\\&/g' ./file.txt
sed -i 's/\_/\\\_/g' ./file.txt

Is this correct?

Unfortunately, the file is too large to open in any GUI software, so checking if my sed line is correct with a text editor is difficult. I tried searching with grep, but the search does not work as expected (e.g. below, I searched for any lines containing “$”):

grep "\$" file.txt

• What is the best way to put “\” in front of these characters?
• How can I use grep to successfully check the lines with the replacements?

Answer 1

You can do the replacement with a single call to sed:

sed -i -E 's/([#$%&_\])/\\&/g' file.txt

The & in the replacement text fills in for whichever single character is enclosed in parentheses. Note that since \ is the LaTeX escape character, you’ll have to escape it as well in the original file.