Nested for loop in bash not iterating properly?

Question

I am new to scripting/programming/everything and can't seem to figure out this bash script/loop I am trying to iterate.

I have a directory called "folder", in which there are many subdirectories which each contain files that I would like to echo (for now)

I have this, but it doesn't seem to print the files within the subdirectories but instead prints the subdirectories themselves. How would I alter the script to make this work?

for directory in *;
do
        for thing in $directory 
        do
                echo $thing
        done
done

Don't you want ${directory}/*? Or perphaps (cd "$directory"; for thing in *; do echo $thing; done;). — Droppy
– Droppy, Commented Aug 10, 2016 at 13:52

chepner · Accepted Answer · 2016-08-10 14:19:32Z

3

The for loop itself doesn't traverse a file system; it only iterates over a sequence of strings. You need to iterate over the result of a pathname expansion for the second loop.

for directory in *;
do
    for thing in "$directory"/*
    do
        echo "$thing"
    done
done

You can do this with one loop with a more complex pattern:

for thing in */*; do
    echo "$thing"
done

edited Aug 10, 2016 at 14:19

answered Aug 10, 2016 at 13:56

chepner

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1 Comment

chepner Over a year ago

By no loop, do you mean something like some_command */*? I'm assuming that the body of the inner loop is more complicated than a single built-in command, in which case this would have problems with large sets of matches.

sjsam · Accepted Answer · 2016-08-10 14:28:49Z

1

Bash version 4.0 adds a new globbing option called globstar which treats the pattern ** differently when it's set.

#!/bin/bash
shopt -s globstar
for file in folder/** # with '**'  bash recurses all the directories
do
  echo "$file"
done

edited Aug 10, 2016 at 14:28

answered Aug 10, 2016 at 13:55

sjsam

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1 Comment

chepner Over a year ago

The array is extraneous, and possibly a drain on memory; you can iterate over the pattern directly, which (I think) doesn't need to store the full match in memory.

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