sed: Replace FIRST occurence of space with newline

Question

I am trying to replace the first occurrence of a space in each line with a newline.

For instance

123 there is a monkey
567 there is also a tiger

would become

123
there is a monkey
567
there is also a tiger

I have tried doing this with the command:

sed -e 's/^\s\+/\n/g' output.txt > new.txt

with no luck. I am also open to any other programs in linux that would allow me to do this such as awk, perl, or bash.

Answer 1

You can use:

sed $'s/ \{1,\}/\\\n/' file
123
there is a monkey
567
there is also a tiger

This works both on BSD as well on gnu sed.