How to escape single quotes within single quoted s

Question

Let's say, you have a bash alias like:

alias rxvt='urxvt'

which works fine.

However:

alias rxvt='urxvt -fg '#111111' -bg '#111111''

won't work, and neither will:

alias rxvt='urxvt -fg \'#111111\' -bg \'#111111\''

So how do you end up matching up opening and closing quotes inside a string once you have escaped quotes?

alias rxvt='urxvt -fg'\''#111111'\'' -bg '\''#111111'\''

seems ungainly although it would represent the same string if you're allowed to concatenate them like that.

Answer 1

Since one cannot put single quotes within single quoted strings, the simplest and most readable option is to use a HEREDOC string

command=$(cat <<'COMMAND'
urxvt -fg '#111111' -bg '#111111'
COMMAND
)

alias rxvt=$command

In the code above, the HEREDOC is sent to the cat command and the output of that is assigned to a variable via the command substitution notation $(..)

Putting a single quote around the HEREDOC is needed since it is within a $()