Shell equality not outputting any results

Question

I'm trying to iterate over a file directory and extract files which have the same id in the range between 5: 10 but are not identical filenames. This script works for the first loop, but won't identify any suitable results in the second output (exits without error). Manually passing in an example of two suitable filenames runs without error. I'm not really sure what's wrong here.

$FILES="data/*"
for f in $FILES; do
    for g in $FILES; do
        if [[ ${f: 5: 10} == ${g: 5: 10} ]]; then
  
            if [[ ${g: -2} != ${f: -2} ]]; then

            echo "$f"
            echo "$g"                        
                    
            fi 
        fi
    done   
done

eg if the data/* contained:

data/wordA_ln
data/wordB_ln
data/wordA_ap
data/wordB_ap

The script would output:

data/wordA_ln
data/wordA_ap

data/wordB_ln
data/wordB_ap

Answer 1

The difficulty here is that you are looping twice on the same files. And ${var: 5: 10} will include, for exemple, wordA_ln or wordA_cp . Therefore these will never be equal.

Anyway, I took another approach. Get a list of filenames, well the portion you want to check:

find data -type f -exec basename {} \; | cut -d'_' -f1 | sort | uniq

Ex:

• find found "data/wordA_ln".
• basename {} will return "wordA_ln".
• | cut -d'_' -f1 | cut -d'_' -f1 will return "wordA".
• | sort | uniq | sort | uniq will remove duplicates.

From that list of possible filenames, do another find in directory data to list the matching files.

Complete script:

#!/bin/bash

while IFS= read -r line
do
    find data -type f -name "*${line}*" -print
    echo ""
done < <(find data -type f -exec basename {} \; | cut -d'_' -f1 | sort | uniq)