Sed substitute recursively

Question

echo ddayaynightday | sed \'s/day//g\'

It ends up daynight

Is there anyway to make it substitute until no more match ?

Answer 1

The following works:

$ echo ddayaynightday | sed ':loop;/day/{s///g;b loop}'
night

Depending on your system, the ; may not work to separate commands, so you can use the following instead:

echo ddayaynightday | sed -e ':loop' -e '/day/{s///g
                                               b loop}'

Explanation:

:loop       # Create the label 'loop'
/day/{      # if the pattern space matches 'day'
  s///g     # remove all occurrence of 'day' from the pattern space
  b loop    # go back to the label 'loop'
}

If the b loop portion of the command is not executed, the current contents of the pattern space are printed and the next line is read.