问题
I often use ./*/ in a for loop like
for d in ./*/; do
: # do something with dirs
done
to match all non-hidden directories in current working directory, but I'm not really sure if this is a portable way to do that. I have bash, dash and ksh installed on my system and it works with all, but since POSIX spec doesn't say anything about it (or it says implicitly, and I missed it) I think I can't rely on it. I also checked POSIX bug reports, but to no avail, there's no mention of it there as well.
Is its behaviour implementation or filesystem dependent? Am I missing something here? How do I know if it's portable or not?
回答1:
Short answer: YES
Long Answer:
The POSIX standard (from opengroup) states that / will only match slashes in the expanded file name. Since Unix/Linux does not allow / in the file name, I believe that this is a safe assumption on Unix/Linux systems.
From the bolded text below, it seems that even for systems that will allow / in the file name, the POSIX standard require that / will not be matched to such file.
On Windows, looks like / is not allowed in the file name, but I'm not an expert on Windows.
From Shell Programming Language § Patterns Used for Filename Expansion:
The slash character in a pathname shall be explicitly matched by using one or more slashes in the pattern; it shall neither be matched by the asterisk or question-mark special characters nor by a bracket expression. Slashes in the pattern shall be identified before bracket expressions; thus, a slash cannot be included in a pattern bracket expression used for filename expansion. ...
Additional Note - clarifying pathname:
The pathname is defined in 4.13, with explicit reference to pathname with trailing slash in General Concepts § Pathname Resolution.
A pathname that contains at least one non-<slash> character and that ends with one or more trailing <slash> characters shall not be resolved successfully unless the last pathname component before the trailing <slash> characters names an existing directory or a directory entry that is to be created for a directory immediately after the pathname is resolved. Interfaces using pathname resolution may specify additional constraints when a pathname that does not name an existing directory contains at least one non-<slash> character and contains one or more trailing <slash> characters.
来源：https://stackoverflow.com/questions/58176457/is-portable