tag 11271 notabug thanks On 04/18/2012 05:01 AM, Kevin Huanpeng Du wrote: > Hi, > i find dirname dirname strip a dir name when a string with out a filename. > > ₤ dirname /dir/file > ₤ /dir > ₤ dirname /dir/subdir/ > ₤ /dir # is this right? subdir is a not a file. Thanks for the report. However, this is not a bug. POSIX requires this behavior. In POSIX parlance, a "file" is any entity that can be referenced by name as a member of a directory. There are multiple types of files: regular files, block device files, character device files, sockets, and important to your case, subdirectories. Only subdirectories may have a trailing slash, but the point remains that even without the trailing slash, 'subdir' is a file (of type directory, rather than the more typical type regular file), which can be referenced by name from the directory '/dir'. The POSIX-mandated algorithm for the dirname executable is to strip trailing slashes _before_ removing the trailing file name element, precisely for usage like this: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/dirname.html 1 If string is //, skip steps 2 to 5. 2 If string consists entirely of <slash> characters, string shall be set to a single <slash> character. In this case, skip steps 3 to 8. 3 If there are any trailing <slash> characters in string, they shall be removed. 4 If there are no <slash> characters remaining in string, string shall be set to a single <period> character. In this case, skip steps 5 to 8. 5 If there are any trailing non- <slash> characters in string, they shall be removed. 6 If the remaining string is //, it is implementation-defined whether steps 7 and 8 are skipped or processed. 7 If there are any trailing <slash> characters in string, they shall be removed. 8 If the remaining string is empty, string shall be set to a single <slash> character. And according to that algorithm, even though '/dir/subdir', '/dir/subdir/' and '/dir/subdir/.' all resolve to the same location in the file system, using dirname on the first two gives '/dir' while using 'dirname /dir/subdir/.' gives '/dir/subdir'. -- Eric Blake address@hidden +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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