How to escape single quotes within single quoted strings

Question

Let\'s say, you have a Bash alias like:

alias rxvt=\'urxvt\'

which works fine.

However:

Answer 1

shell_escape () {
    printf '%s' "'${1//\'/\'\\\'\'}'"
}

Implementation explanation:

• double quotes so we can easily output wrapping single quotes and use the ${...} syntax

• bash's search and replace looks like: ${varname//search/replacement}

• we're replacing ' with '\''

• '\'' encodes a single ' like so:

  1. ' ends the single quoting

  2. \' encodes a ' (the backslash is needed because we're not inside quotes)

  3. ' starts up single quoting again

  4. bash automatically concatenates strings with no white space between

• there's a \ before every \ and ' because that's the escaping rules for ${...//.../...} .

string="That's "'#@$*&^`(@#'
echo "original: $string"
echo "encoded:  $(shell_escape "$string")"
echo "expanded: $(bash -c "echo $(shell_escape "$string")")"

P.S. Always encode to single quoted strings because they are way simpler than double quoted strings.