Iterate through list of filenames in order they were created in bash

Question

Parsing output of ls to iterate through list of files is bad. So how should I go about iterating through list of files in order by which they were first created

Answer 1

Here's a way using stat with an associative array.

n=0
declare -A arr
for file in *; do
    # modified=$(stat -f "%m" "$file") # For use with BSD/OS X
    modified=$(stat -c "%Y" "$file") # For use with GNU/Linux
    # Ensure stat timestamp is unique
    if [[ $modified == *"${!arr[@]}"* ]]; then
        modified=${modified}.$n
        ((n++))
    fi
    arr[$modified]="$file"
done
files=()
for index in $(IFS=$'\n'; echo "${!arr[*]}" | sort -n); do
    files+=("${arr[$index]}")
done

Since sort sorts lines, $(IFS=$'\n'; echo "${!arr[*]}" | sort -n) ensures the indices of the associative array get sorted by setting the field separator in the subshell to a newline.

The quoting at arr[$modified]="${file}" and files+=("${arr[$index]}") ensures that file names with caveats like a newline are preserved.

Answer 2

With all of the cautions and warnings against using ls to parse a directory notwithstanding, we have all found ourselves in this situation. If you do find yourself needing sorted directory input, then about the cleanest use of ls to feed your loop is ls -opts | read -r name; do... This will handle spaces in filenames, etc.. without requiring a reset of IFS due to the nature of read itself. Example:

ls -1rt | while read -r fname; do  # where '1' is ONE not little 'L'

So do look for cleaner solutions avoiding ls, but if push comes to shove, ls -opts can be used sparingly without the sky falling or dragons plucking your eyes out.

let me add the disclaimer to keep everyone happy. If you like newlines inside your filenames -- then do not use ls to populate a loop. If you do not have newlines inside your filenames, there are no other adverse side-effects.

Contra: TLDP Bash Howto Intro:

    #!/bin/bash
    for i in $( ls ); do
        echo item: $i
    done

It appears that SO users do not know what the use of contra means -- please look it up before downvoting.