When I'm using a POSIX compliant shell (es: dash, bash, zsh, ...) can I be sure that * will always expand in alphabetical order (dictated by LC_COLLATE)?
example:
$ echo 1 > file_a
$ echo 2 > file_b
$ echo 3 > file_c
$ cat *
1
2
3
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S1cK94
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See also What is the sort order when using conditional operators?, which has a little more detail. – Adam Katz Oct 10 '21 at 19:31
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1Does this answer your question? What is the sort order when using conditional operators? – Adam Katz Oct 10 '21 at 19:32
2 Answers
2
That behavior is required by POSIX, and you're safe to rely on it.
Another note that you want to set your locale to C to get consistent behavior. In locale with collation elements have the same sorting order, you will have strange result.
On GNU system with UTF-8 locale:
$ printf '%b\n' '\U2461' '\U2460' | sort
②
①
or:
$ printf '%s\n' A B a b | sort
a
A
b
B
Setting to C locale:
$ printf '%b\n' '\U2461' '\U2460' | LC_ALL=C sort
①
②
$ printf '%s\n' A B a b | LC_ALL=C sort
A
B
a
b
Some shells even do not support multibyte characters like dash, mksh or support but will choke on invalid sequences of bytes like yash.
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Another reason to stick to
LC_COLLATE=Cis that some shells don't support multibyte characters in pattern matching (e.g. dash, mksh). – Gilles 'SO- stop being evil' Nov 18 '15 at 22:26 -
@Gilles: Ah, right, it's fair enough. I added it to my answer, thanks. – cuonglm Nov 19 '15 at 01:34
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Yes. The normative answer can be found here:
If the pattern matches any existing filenames or pathnames, the pattern shall be replaced with those filenames and pathnames, sorted according to the collating sequence in effect in the current locale.
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