Replace slash in Bash

Question

Let\'s suppose I have this variable:

DATE=\"04/Jun/2014:15:54:26\".

Therein I need to replace / with \\/ in order to

Answer 1

This has not been said in other answers so I thought I'd add some clarifications:

tr uses two sets of characters for replacement, and the characters from the first set are replaced with those from the second set in a one-to-one correspondance. The manpage states that

SET2 is extended to length of SET1 by repeating its last character as necessary. Excess characters of SET2 are ignored.

Example:

echo abca | tr ab de    # produces decd
echo abca | tr a de     # produces dbcd, 'e' is ignored
echo abca | tr ab d     # produces ddcd, 'd' is interpreted as a replacement for 'b' too

When using sed for substitutions, you can use another character than '/' for the delimiter, which will make your expression clearer (I like to use ':', @n34_panda proposed '#' in their answer). Don't forget to use the /g modifier to replace all occurences: sed 's:/:\\/:g' with quotes or sed s:/:\\\\/:g without (backslashes have to be escaped twice).

Finally your shortest solution will probably be @Luc-Olivier's answer, involving substitution, in the following form (don't forget to escape forward slashes too when part of the expected pattern):

echo ${variable/expected/replacement}     # will replace one occurrence
echo ${variable//expected/replacement}    # will replace all occurrences