Replace backslash("\") with forward slash("/") in a variable in bash

Question

I want to replace backslash(\) with forward slash(/) in a variable in bash. I tried it like this, but it doesn't work:

home_mf = ${home//(\)//(/)}

For example, I would like

\a\b\c -> /a/b/c

Answer 1

The correct substitution is

home_mf="${home//\\//}"

This breaks up as follows:

• // replace every
• \\ backslash
• / with
• / slash

Demonstration:

$ t='\a\b\c'; echo "${t//\\//}"
/a/b/c

---

An alternative that may be easier to read would be to quote the pattern ('\' rather than \\) and the replacement ("/" rather than plain /):

home_mf="${home//'\'/"/"}"

Answer 2

This will do it:

home_mf=${home//\//\\} # forward to backward slash
home_mf=${home//\\//} # backward to forward slash

e.g.:

$ cat slash.sh
#!/bin/bash
set -x
home=/aa/bb/cc       
home_mf=${home//\//\\}
echo $home_mf
home_mf=${home_mf//\\//}
echo $home_mf
$ ./slash.sh
+ home=aa/bb/cc
+ home_mf='\aa\bb\cc'
+ echo '\aa\bb\cc'
\aa\bb\cc
+ home_mf=/aa/bb/cc
+ echo /aa/bb/cc
/aa/bb/cc

The ${variable/..} syntax is ksh, bash, and possibly other shells specific but is not be present in all Bourne shell syntax based shells, e.g. dash. Should you want a portable way (POSIX), you might use sed instead:

home_mf=$(printf "%s" "$home" | sed 's/\//\\/g')    # forward to backward slash
home_mf=$(printf "%s" "$home_mf" | sed 's/\\/\//g') # backward to forward slash