Replace forward slash with double backslash enclosed in double quotes

Question

I'm desperately trying to replace a forward slash (/) with double backslash enclosed in double quotes ("\\")

but

a=`echo "$var" | sed 's/^\///' | sed 's/\//\"\\\\\"/g'`

does not work, and I have no idea why. It always replaces with just one backslash and not two

Answer 1

When / is part of a regular expression that you want to replace with the s (substitute) command of sed, you can use an other character instead of slash in the command's syntax, so you write, for example:

sed 's,/,\\\\,g'

above , was used instead of the usual slash to delimit two parameters of the s command: the regular expression describing part to be replaced and the string to be used as the replacement.

The above will replace every slash with two backslashes. A backslash is a special (quoting) character, so it must be quoted, here it's quoted with itself, that's why we need 4 backslashes to represent two backslashes.

$ echo /etc/passwd| sed 's,/,\\\\,g'
\\etc\\passwd