Sorting an array of pathnames (strings) [Bash]

Question

I have seen way too many duplicates of this, but none of the answer codes or tips ever helped me, so I'm left confused.

input=/foo/bar/*;
#Contains something along the lines of 
#/foo/bar/file1 /foo/bar/file2 /foo/bar/file3
#And I simply need
#/foo/bar/file3 /foo/bar/file2 /foo/bar/file1

output=($(for l in ${input[@]}; do echo $l; done | sort));
#Doesn't work, returns only the last entry from input

output=$(sort -nr ${input});
#Works, returns everything correctly reversed, but outputs the file contents and not the pathnames;
output=($(sort -nr ${input}));
#Outputs only the last entry and also its contents and not the pathname;

I tried many more options, but I'm not gonna fill this whole page with them, you get the gist.

Duplicates: (None of them helpful to me)

How can I sort the string array in linux bash shell?

How to sort an array in BASH

custom sort bash array

Sorting bash arguments alphabetically

$input is not an array, it's a string. Also, how is ${a[@]} populated? — choroba
– choroba, Commented Sep 19, 2016 at 21:17
@choroba Ops, I just copy and pasted from the other SO question because I didn't have the code anymore. — niraami
– niraami, Commented Sep 19, 2016 at 21:22
input contains exactly the string /foo/bar/*; pathname expansion does not occur in assignment statements. — chepner
– chepner, Commented Sep 20, 2016 at 0:59

glenn jackman · Accepted Answer · 2016-09-19 21:21:09Z

3

You're confused about what is an array in bash: this does not declare an array:

input=/foo/bar/*

$input is just the string "/foo/bar/*" -- the list of files does not get expanded until you do something like for i in ${input[@]} where the "array" expansion is unquoted.

You want this:

input=( /foo/bar/* )
mapfile -t output < <(printf "%s\n" "${input[@]}" | sort -nr)

I don't have time to explain it. I'll come back later.

answered Sep 19, 2016 at 21:21

glenn jackman

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2 Comments

niraami Over a year ago

Yeah, that's probably it. I'm pretty new to Bash, and considering nearly every list-type structure in C++, Lua, Python... (VB.NET - but I don't want to talk about that) is an array I automatically assumed the same here.

chepner Over a year ago

bash is very poor in data structures, because it wasn't designed to process data; it's a glue language to facilitate running other programs.

anubhava · Accepted Answer · 2016-09-19 21:21:38Z

1

You can use sort -r with printf, where input containg glob string to match your filenames:

sort -r <(printf "%s\n" $input)

edited Sep 19, 2016 at 21:21

answered Sep 19, 2016 at 21:20

anubhava

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4 Comments

niraami Over a year ago

Agreed, really clever, compact and intuitive. Thank you!

chepner Over a year ago

Beware, though: it also doesn't work if the value of input contains any whitespace.

anubhava Over a year ago

Yes I know about files with spaces but as per OP has filenames as /foo/bar/file1 /foo/bar/file2 /foo/bar/file3. Besides I've tested this with filenames with spaces as well. I think filenames with newlines will have issues though.

niraami Over a year ago

Yeah, I have no intention of using spaces in my pathnames, it's a static directory with set (by me) filenames - I just wanted for it to be a little modular.

Juan Tomas · Accepted Answer · 2016-09-19 21:19:48Z

0

This works:

input=`foo/bar/*`
output=`for l in $input ; do echo $l ; done | sort -r`

answered Sep 19, 2016 at 21:19

Juan Tomas

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