bash shell - increment (associative) array value

Question

Just want to share with you something I did not easily find by myself...

I am a newbie in shell script and was just wondering how can I increment a value of a an associative array.

Let's assume this script:

#!/bin/bash

declare -A b # declare an associative array 

a="aaa"
b[$a]=1

echo ${b[@]} # display all the values
echo ${b[$a]} # display the first value (1)
echo ${b[aaa]} # display the first value as well (1)

The solution can be

((b[$a]++))
echo ${b[@]} # display 2

Now that I found it, it seems evident, but I spent some time to get it...

I hope this can save some time to people :)

@９９９９９９９９９９９９９９９９９９９９９９９９９９９９９９There are a few glitches with the way Bash parses arithmetic: for example, try it with these keys: a=' ', a=@, a=*, gniourf=hello; a='$gniourf' or even better: a='hi$(ls>&2)' (and you're glad I only put a friendly command there). Surprise. — gniourf_gniourf
– gniourf_gniourf, Commented Oct 15, 2015 at 14:00

Bast · Accepted Answer · 2015-10-15 14:16:55Z

3

As describe above, the solution can be

((b[$a]++)) #  or (('b[$a]'++)) for a more secure way as pointed by @gniourf_gniourf
echo ${b[@]} # display 2

Now that I found it, it seems evident, but I spent some time to get it...

I hope this can save some time to people :)

edited Oct 15, 2015 at 14:16

answered Oct 15, 2015 at 13:40

Bast

6712 gold badges8 silver badges23 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

bash shell - increment (associative) array value

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related