splitting a string into individual characters in bash using IFS

Question

I'm trying to split a string into individual characters. For example temp="hello" into "h", "e", "l", "l", "o"

I tried using IFS because that's what I used in previous string splits and wanted to keep the consistency across the script. IFS='' read h e l l o <<<"$temp" does not work. What am I doing wrong?

@EtanReisner So is there NO absolute way to do a blank split using IFS? — Krin123
– Krin123, Commented Sep 3, 2015 at 20:18
There's no "split every character" trick with IFS that I'm aware of. You could probably read -n 1 -r char in a loop though. — Etan Reisner
– Etan Reisner, Commented Sep 3, 2015 at 20:19

anubhava · Accepted Answer · 2015-09-03 20:16:40Z

6

You can use fold:

arr=($(fold -w1 <<< "$temp"))

Verify:

declare -p arr
declare -a arr='([0]="h" [1]="e" [2]="l" [3]="l" [4]="o")'

answered Sep 3, 2015 at 20:16

anubhava

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2 Comments

Krin123 Over a year ago

Is there a way to do the same thing with IFS?

anubhava Over a year ago

No IFS based splitting on individual character. There are many other tricks available like grep -o . <<< "$temp" or even awk

chepner · Accepted Answer · 2015-09-04 14:32:55Z

TL;DR: this is just to see if it can be done. Use fold like anubhava suggests; starting a single process is a small price to pay to avoid not one, but two uses of eval.

I wouldn't actually use this (I think it's safe, but I wouldn't swear to it, and boy, is it ugly!), but you can use eval, brace expansion, and substring parameter expansion to accomplish this.

$ temp=hello
$ arr=( $(eval echo $(eval echo \\\${temp:{0..${#temp}}:1})) )
$ printf '%s\n' "${arr[@]}"
h
e
l
l
o

How does this work? Very delicately. First, the shell expands ${#temp} to the length of the variable whose contents we want to split. Next, the inner eval turns the string \${temp:{0..5}:1} into a set of strings ${temp:0:1}, ${temp:1:1}, etc. The outer eval then performs the parameter expansions that produce one letter each from temp, and those letters provide the contents of the array.

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