bash: how for loop sorts files when iterating

Question

What is the default behavior of for loop in terms of sorting when listing files in a directory?

e.g.

for sqlfile in *.sql; do mysql -u root -p pass < sqlfile; done

Is this documented somewhere?

It does not sort ever. It is the glob (*.sql) that is doing the sorting. — ctrl-alt-delor, May 30 '18 at 09:41

l0b0 · Answer 1 · 2018-05-30T20:46:31.740

3

According to man bash's section on "Pathname Expansion":

If one of these characters appears, then the word is regarded as a pattern, and replaced with an alphabetically sorted list of filenames matching the pattern […]

This sorting depends on the value of $LC_COLLATE:

This variable determines the collation order used when sorting the results of pathname expansion […]

As you can see from the above, this has nothing to do with the for loop. Globs can be used in many ways, and their expansion is always sorted.

edited May 30 '18 at 20:46

answered May 30 '18 at 09:40

l0b0

51,350

2

for does not sort ever. It is the glob (*.sql) that is doing the sorting. – ctrl-alt-delor May 30 '18 at 09:42
Sure, I'm just explaining how the sorting that happens in the for loop works. – l0b0 May 30 '18 at 09:43
1

For me to accept the answer, the comment of ctrl-alt-delor on the glob should be added. – pkaramol May 30 '18 at 09:44
+1 for the LC_COLLATE observation. – Rui F Ribeiro May 30 '18 at 09:47

score 2 · Answer 2 · answered May 30 '18 at 09:45

for loops don't sort, they give you the values in exactly the order they were presented:

$ for x in b a c ; do echo $x ; done
b
a
c

Globs, on the other hand, do sort alphabetically, regardless of if you use them in a for or anywhere else:

$ touch b a c
$ echo *
a b c

bash: how for loop sorts files when iterating

2 Answers2