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, Sep 03 '15 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, Sep 03 '15 at 20:19

score 6 · Accepted Answer · answered Sep 03 '15 at 20:16

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 03 '15 at 20:16

anubhava

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Is there a way to do the same thing with IFS? – Krin123 Sep 03 '15 at 20:18
No `IFS` based splitting on individual character. There are many other tricks available like `grep -o . <<< "$temp"` or even `awk` – anubhava Sep 03 '15 at 20:21

score 1 · Answer 2 · answered Sep 04 '15 at 14:32

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.

splitting a string into individual characters in bash using IFS

2 Answers2