I am trying to write a Perl one-liner in a Bash script to change math-mode delimiters in a LaTeX file from "\[" and "\]" to dollar signs.
That is, I want to change \[a + b = c\] to $a + b = c$.
Unfortunately, I can't figure out how to escape the dollar sign in Perl correctly.
The closest I've gotten is to use perl -pi -e 's/\[/\$/gm' file.tex. However, this inserts \$ into the file instead of a single dollar sign.
You aren't inserting \$; you are simply only replacing the [, not \[, with a dollar sign. Compare:
# Wrong
$ perl -p -e 's/\[/\$/gm' tmp.txt
\$a + b = c\]
# Right
$ perl -p -e 's/\\\[/\$/gm' tmp.txt
$a + b = c\]
To replace both,
$ perl -p -e 's/\\\[|\\\]/\$/gm' tmp.txt
$a + b = c$
For what it's worth, you can do this with the standard editor ed, rather than perl, though the escaping gets a little hairy (even switching to tripleee's simpler regular expression for matching either delimiter; it looks the same, but the double \\ are there for printf, not ed, since I'm using | in the substitution operator.):
$ cat tmp.txt
\[a + b = c\]
$ printf 's|\\\[][]|$|g\nwq\n' | ed tmp.txt
14
12
$ cat tmp.txt
$a + b = c$
No, the problem is that you are replacing a (backslash-escaped) literal [ with a (backslash-escaped) literal dollar sign, but not matching or replacing the literal backslash at all.
Try this.
perl -pi -e 's/\\[][]/\$/g' file.tex
The /m flag didn't seem useful so I took it out.
The square brackets are a character class [...] containing the two literal characters ] and [. They have to be in this order, to keep the expression unambiguous (though it also looks funny). And of course, \\ is a (backslash-escaped) literal backslash.
$without backslash?$. Results in an error:Final $ should be \$ or $name at -e line 1, within string