Bash script: split word on each letter

Question

How can I split a word's letters, with each letter in a separate line?

For example, given "StackOver" I would like to see

S
t
a
c
k
O
v
e
r

I'm new to bash so I have no clue where to start.

Answer 1

I would use grep:

$ grep -o . <<<"StackOver"
S
t
a
c
k
O
v
e
r

or sed:

$ sed 's/./&\n/g' <<<"StackOver"
S
t
a
c
k
O
v
e
r

And if empty space at the end is an issue:

sed 's/\B/&\n/g' <<<"StackOver"

All of that assuming GNU/Linux.

Answer 2

You may want to break on grapheme clusters instead of characters if the intent is to print text vertically. For instance with a e with an acute accent:

• With grapheme clusters (e with its acute accent would be one grapheme cluster):

  $ perl -CLAS -le 'for (@ARGV) {print for /\X/g}' $'Ste\u301phane'
  S
  t
  é
  p
  h
  a
  n
  e
  

  (or grep -Po '\X' with GNU grep built with PCRE support)

• With characters (here with GNU grep):

  $ printf '%s\n' $'Ste\u301phane' | grep -o .
  S
  t
  e
  
  p
  h
  a
  n
  e
  

• fold is meant to break on characters, but GNU fold doesn't support multi-byte characters, so it breaks on bytes instead:

  $ printf '%s\n' $'Ste\u301phane' | fold -w 1
  S
  t
  e
  �
  �
  p
  h
  a
  n
  e
  

On StackOver which only consists of ASCII characters (so one byte per character, one character per grapheme cluster), all three would give the same result.

Answer 3

If you have perl6 in your box:

$ perl6 -e 'for @*ARGS -> $w { .say for $w.comb }' 'cường'       
c
ư
ờ
n
g

work regardless of your locale.

Answer 4

With many awk versions

awk -F '' -v OFS='\n' '{$1=$1};1' <<<'StackOver'

Answer 5

You can use the fold (1) command. It is more efficient than grep and sed.

$ time grep -o . <bigfile >/dev/null

real    0m3.868s
user    0m3.784s
sys     0m0.056s
$ time fold -b1 <bigfile >/dev/null

real    0m0.555s
user    0m0.528s
sys     0m0.016s
$

One significant difference is that fold will reproduce empty lines in the output:

$ grep -o . <(printf "A\nB\n\nC\n\n\nD\n")
A
B
C
D
$ fold -b1 <(printf "A\nB\n\nC\n\n\nD\n")
A
B

C


D
$ 

Answer 6

echo StackOver | sed -e 's/./&\n/g'
S
t
a
c
k
O
v
e
r

Answer 7

You can handle multibyte characters like:

<input \
dd cbs=1 obs=2 conv=unblock |
sed -e:c -e '/^.*$/!N;s/\n//;tc'

Which can be pretty handy when you're working with live input because there's no buffering there and a character is printed as soon it is whole.

Answer 8

The below will be generic:

$ awk -F '' \
   'BEGIN { RS = ""; OFS = "\n"} {for (i=1;i<=NF;i++) $i = $i; print }' <file_name>

Answer 9

Also Python 2 can be used from the command line:

python <<< "for x in 'StackOver':
   print x"

or:

echo "for x in 'StackOver':
    print x" | python

or (as commented by 1_CR) with Python 3:

python3 -c "print(*'StackOver',sep='\n')"

Answer 10

Since you specifically asked for an answer in bash, here's a way to do it in pure bash:

while read -rn1; do echo "$REPLY" ; done <<< "StackOver"

Note that this will catch the newline at the end of the "here document". If you want to avoid that, but still iterate over the characters with a bash loop, use printf to avoid the newline.

printf StackOver | while read -rn1; do echo "$REPLY" ; done

Answer 11

You may use word boundaries also..

$ perl -pe 's/(?<=.)(\B|\b)(?=.)/\n/g' <<< "StackOver"
S
t
a
c
k
O
v
e
r

Answer 12

In bash:

This works with any text and with only bash internals (no external utility called), so, should be fast on short strings.

str="StackOvér áàéèëêếe"

[[ $str =~ ${str//?/(.)} ]]           # Use a regex to split.
printf '%s\n' "${BASH_REMATCH[@]:1}"  # Print all characters.

Output:

S
t
a
c
k
O
v
é
r
 
á
à
é
è
ë
ê
ế
e

Answer 13

s=stackoverflow;

$ time echo $s | fold -w1                                                                                                                                          
s                                                                                                                                                                          
t                                                                                                                                                                          
a                                                                                                                                                                          
c                                                                                                                                                                          
k                                                                                                                                                                          
o                                                                                                                                                                          
v
e
r

real    0m0.014s
user    0m0.000s
sys     0m0.004s

updates here is the hacky|fastest|pureBashBased way !

$ time eval eval printf \'%s\\\\n\' \\\${s:\{0..$((${#s}-1))}:1}
s
t
a
c
k
o
v
e
r

real    0m0.001s
user    0m0.000s
sys     0m0.000s

for more awesomeness

function foldh () 
{ 
    if (($#)); then
        local s="$@";
        eval eval printf \'%s\\\\n\' \\\"\\\${s:\{0..$((${#s}-1))}:1}\\\";
    else
        while read s; do
            eval eval printf \'%s\\\\n\' \\\"\\\${s:\{0..$((${#s}-1))}:1}\\\";
        done;
    fi
}
function foldv () 
{ 
    if (($#)); then
        local s="$@";
        eval eval echo \\\"\\\${s:\{0..$((${#s}-1))}:1}\\\";
    else
        while read s; do
            eval eval echo \\\"\\\${s:\{0..$((${#s}-1))}:1}\\\";
        done;
    fi
}

Answer 14

read -a var <<< $(echo "$yourWordhere" | grep -o "." | tr '\n' ' ')

this will split your word and store it in array var.

Answer 15

for x in $(echo "$yourWordhere" | grep -o '.')
do
    code to perform operation on individual character $x of your word
done

Answer 16

On bash 4.2 and up (I tested 4.2.46 and 5.1), with extglobs you can use and empty "zero or one" match:

# shopt -s extglob
# V="StackOverflow"
# echo -e ${V//?()/\\n}
S
t
a
c
k
O
v
e
r
f
l
o
w

It also works to split your string into an array:

# A=( ${V//?()/ } )
# declare -p A

declare -a A='([0]="S" [1]="t" [2]="a" [3]="c" [4]="k" [5]="O" [6]="v" [7]="e" [8]="r" [9]="f" [10]="l" [11]="o" [12]="w")'

Answer 17

Using Raku (formerly known as Perl_6)

~$ echo "StackOvér áàéèëêếe" | raku -ne '.chars.put;'
18
~$ echo "StackOvér áàéèëêếe" | raku -ne '.put for .comb;'
S
t
a
c
k
O
v
é
r

á
à
é
è
ë
ê
ế
e

https://raku.org/