How to replace spaces with newlines/enter in a text-file?

A few choices:

1. The classic, use tr:

   tr ' ' '\n' < example
   

2. Use cut

   cut -d ' ' --output-delimiter=$'\n' -f 1- example
   

3. Use sed

   sed 's/ /\n/g' example
   

4. Use perl

   perl -pe 's/ /\n/g' example
   

5. Use the shell

   foo=$(cat example); echo -e ${foo// /\\n}
   

Try the below command

awk -v RS=" " '{print}' file

OR

awk -v RS='[\n ]' '{print}' file

Example:

$ awk -v RS=" " '{print}' example
abc
cdef
ghi
jk
lmnopq
rst
uv
wxyz

Explanation:

RS (Record seperator) is an built-in awk variable. In the first command, the value given to the Record separator variable is space. so awk breaks the line from printing whenever it finds a space.

In the second command, the value given to the RS variable is space or a new line character.This command eliminates the extra blank line appeared while running the first command.

You can use xargs,

cat example | xargs -n 1

or, better

xargs -n 1 < example