mjhjmtu

I've one string with this format:

A B C D

How can I have the same pattern in a column?

Starting with this string:

s='A B C D'

If we want to make it print as a column, we can use bash:

$ echo "$s// /$'n'"
A
B
C
D

Or, using sed:

$ sed 's/ /n/g' <<<"$s"
A
B
C
D

Or, using tr:

$ tr ' ' 'n' <<<"$s"
A
B
C
D

Or, using awk:

$ awk '$1==$1' RS=' ' ORS='n' <<<"$s"
A
B
C
D

Or, using grep:

$ grep -o '[[:alpha:]]' <<<"$s"
A
B
C
D

$ printf '%sn' A B C D
A
B
C
D

The printf command, which is a built-in command in most shells, takes a formatting string containing one or several placeholders. The %s string is the placeholder for "a string" (which is what you have most commonly in the shell). If there are more arguments given to printf then there are placeholders in the format string (as in this case), the whole format string will be applied again and again until the argument list is exhausted. Since there is a n (newline) at the end of the format string, you will therefore get each letter on its own line.

If you have the string in a variable:

str='A B C D'
printf '%sn' $str

This will have the same result as above. The $str expansion is unquoted, which means that the string's content will be split on the spaces (the characters in the variable IFS will be used to split the string into words, and this variable contains by default a space, tab and a newline). Note that if the string contains filename globbing characters, such as *, then the filenames matching these patterns will be outputted. By setting the noglob shell option (with set -f or set -o noglob), you may avoid this:

str='A B C D *'
set -f
printf '%sn' $str
set +f