How to create a dictionary from a text file in bash?

Question

I want to create a dictionary in bash from a text file which looks like this:

H96400275|A
H96400276|B
H96400265|C
H96400286|D

Basically I want a dictionary like this from this file file.txt:

KEYS        VALUES
H96400275 = A
H96400276 = B
H96400265 = C
H96400286 = D

I created following script:

#!/bin/bash
declare -a dictionary

while read line; do 

  key=$(echo $line | cut -d "|" -f1)
  data=$(echo $line | cut -d "|" -f2)
  dictionary[$key]="$data"
done < file.txt


echo ${dictionary[H96400275]}

However, this does not print A, rather it prints D. Can you please help ?

Don't create an additional subshell for each call to cut simply use parameter expansions key="${line%|*}" and data="${line#*|}", or just dictionary[${line%|*}]=${line#*|} (after fixing the -a to -A problem) — David C. Rankin
– David C. Rankin, Commented Nov 19, 2019 at 7:23
There is more than one remark on this post! Please consider smart oguz ismail's answer — F. Hauri - Give Up GitHub
– F. Hauri - Give Up GitHub, Commented Nov 19, 2019 at 8:39

oguz ismail · Accepted Answer · 2019-11-19 07:40:46Z

8

Associative arrays (dictionaries in your terms) are declared using -A, not -a. For references to indexed (ones declared with -a) arrays' elements, bash performs arithmetic expansion on the subscript ($key and H96400275 in this case); so you're basically overwriting dictionary[0] over and over, and then asking for its value; thus D is printed.

And to make this script more effective, you can use read in conjunction with a custom IFS to avoid cuts. E.g:

declare -A dict

while IFS='|' read -r key value; do
    dict[$key]=$value
done < file

echo "${dict[H96400275]}"

See Bash Reference Manual § 6.7 Arrays.

edited Nov 19, 2019 at 7:40

answered Nov 19, 2019 at 7:09

oguz ismail

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1 Comment

David C. Rankin Over a year ago

That's another good way to avoid to subshells associated with calling cut.

torbatamas · Accepted Answer · 2019-11-19 07:11:41Z

5

the only problem is that you have to use -A instead of -a

      -a     Each name is an indexed array variable (see Arrays above).
      -A     Each name is an **associative** array variable (see Arrays above).

answered Nov 19, 2019 at 7:11

torbatamas

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Comments

Romeo Ninov · Accepted Answer · 2019-11-19 07:23:48Z

0

What you want to do is so named associative array. And to declare it you need to use command:

declare -A dictionary

edited Nov 19, 2019 at 7:23

answered Nov 19, 2019 at 7:09

Romeo Ninov

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