8

This is a homework question:

Match all filenames with 2 or more characters that start with a lower case letter, but do not end with an upper case letter.

I do not understand why my solution is not working.

So I executed the below:

touch aa
touch ha
touch ah
touch hh
touch a123e
touch hX
touch Ax

ls [a-z]*[!A-Z]

Output:

aa  ha

My question: Why did it not match "ah", "hh", or "a123e"?

  • Works for me properly under mksh shell, but not bash --posix, so there's gotta be some specific rule for bash` – Sergiy Kolodyazhnyy Jan 19 '17 at 0:32
  • @Serg, note that the behaviour for [A-Z] is unspecified by POSIX except in the C locale. mksh like zsh's [A-Z] doesn't match on É for instance. ksh93's [A-Z] matches on É but not on h. – Stéphane Chazelas Jan 19 '17 at 10:38
9

This is a locale problem. In your locale, [A-Z] expands to something like [AbBcZ...zZ] (plus probably others like accented characters), therefore [^A-Z] actually means "files that end with a" in your example (and only in your example).

If you want to avoid such a surprise, one way is to set LC_COLLATE=C since the collation is the part of your locale settings that is responsible of the sorting order. Also, empty LC_ALL if it is set, as it would take precedence.

$ ls [a-z]*[^A-Z]
aa  ha

$ ( LC_ALL=; LC_COLLATE=C; ls [a-z]*[^A-Z] )
a123e  aa  ah  ha  hh

Or, better, it's probably preferable to not change your locale settings and use the appropriate classes: [:lower:] instead of [a-z] and [:upper:] instead of [A-Z].

$ ls [[:lower:]]*[^[:upper:]]
a123e  aa  ah  ha  hh

Or use bash's globasciiranges option:

$ shopt -s globasciiranges
$ ls [a-z]*[^A-Z]
a123e  aa  ah  ha  hh

$ shopt -u globasciiranges
$ ls [a-z]*[^A-Z]
aa  ha
  • @heemayl, no LC_ALL=C ls [a-z]*[^A-Z] would only affect ls's locale, not the locale used by the shell to expand the glob or parse that command line. – Stéphane Chazelas Jan 19 '17 at 10:01
  • You don't need to export LC_xxx for it to apply to the glob, but it would be preferable so ls gets the same locale. – Stéphane Chazelas Jan 19 '17 at 10:10
  • 1
    Note that in a locale where the charset is GB18030 for instance, with the LC_ALL=C approach, it would fail to match on a file called test-鏏 for instance because once you change the charset to that of the C locale, becomes <0xe7>A. IOW, when changing LC_CTYPE, you're getting different characters. – Stéphane Chazelas Jan 19 '17 at 10:29
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    Note that I suspect [A-Z] in the OP's locale covers more than AbBcC...zZ. It probably also has é, Á (but probably not Ź). IOW, using [A-Z] makes little sense outside the C locale. – Stéphane Chazelas Jan 19 '17 at 10:31
  • @StéphaneChazelas Thank you for you excellent feedback. Answer updated. I believe I took everything into account. – xhienne Jan 19 '17 at 12:14

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