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| From: | Erik Auerswald |
| Subject: | bug#13295: Possible bug - tr utility |
| Date: | Sat, 29 Dec 2012 00:46:51 +0100 |
| User-agent: | Mozilla/5.0 (X11; Linux i686; rv:10.0.11) Gecko/20121123 Icedove/10.0.11 |
Hi Randy, On 12/28/2012 06:37 PM, Killen, Randy wrote:
Hello - I encountered the situation shown below so thought that I would report it to see if it might be a bug or is expected behavior. Please let me know if you need additional information. Randy $ $ echo something | tr [:lower:] [:upper:] SOMETHING $ echo something | tr '[:lower:]' '[:upper:]' SOMETHING $ $ touch l $ echo something | tr [:lower:] [:upper:] tr: misaligned [:upper:] and/or [:lower:] construct $ echo something | tr '[:lower:]' '[:upper:]' SOMETHING $ rm l $ $ touch u $ echo something | tr [:lower:] [:upper:] tr: misaligned [:upper:] and/or [:lower:] construct $ echo something | tr '[:lower:]' '[:upper:]' SOMETHING $ rm u $ $ touch l $ touch u $ echo something | tr [:lower:] [:upper:] something $ echo something | tr '[:lower:]' '[:upper:]' SOMETHING $ rm l $ rm u
This is expected behavior, caused by lack of quoting that results in the shell (Bash) interpreting [...] as a wildcard pattern for file name globbing (see glob(7)). If the 'nullglob' option of the shell is disabled (use 'shopt nullglob' to display the current setting), a wildcard that matches no files is kept as is. Thus the wildcards [:lower:] and [:upper:] are either replaced by l resp. u if one of those files exist or kept, if no matching file exists.
Quoting the special characters '[' and ']' by using '[:lower:]' resp. '[:upper:]' (including the quotes) inhibits the shell from interpreting them as file globbing wildcards. Therefore, you should always quote character classes that are meant as arguments to a program.
HTH Erik
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