From Bugzilla Helper: User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4.2) Gecko/20040308 Description of problem: POSIX defines sysconf(_SC_HOST_NAME_MAX) as returning the maximum size for the system hostname (as set by sethostname()). In practice, this is limited by the kernel to the size of the utsname field in which it us stored, which is defined in sys/utsname.h (actually in bits/utsname.h) as 64. However, sysconf(_SC_HOST_NAME_MAX) returns -1 and does not alter errno, indicating that there is no limit on the length of a hostname. Version-Release number of selected component (if applicable): glibc-2.3.2-95.20 How reproducible: Always Steps to Reproduce: 1. compile and run the program at http://www.msbit.com/LSB/hostname.c Actual Results: The program prints -1 (0) Expected Results: The program should print 64 (0) Additional info:
Current CVS glibc returns 64 (since 2004-03-12), but I don't think it is right either. _POSIX_HOST_NAME_MAX is 255 and the standard says it must be at least _POSIX_HOST_NAME_MAX. In the description of {,_SC_}HOST_NAME_MAX there is no word about sethostname though, just that gethostname never returns a longer name. So I think using HOST_NAME_MAX 255 would be ok too.
You are right ... sethostname() is not in POSIX at all ... and so I believe it is theoretically OK to make HOST_NAME_MAX 255. An application would then know that if it provides a 255 byte buffer to gethostname(), it will work (or at leat, it won't fail because the buffer is too small). Of course, there is the *suggestion* that you can *set* the hostname to this length, which you currently can't. I think the current CVS solution, of returning 64, is the best all round: ask the system how long a host name can be, set the host name to something no longer, & it should work (with appropriate privilege). It would be very weird if [gs]ethostname() had different max name lengths. I suppose we could add to the LSB a warning that the lengths are different for get/sethostname, just as we could add a warning that we have reduced _POSIX_HOST_NAME_MAX from 255 to 64. [[whichever path you choose, I will try and ensure that the LSB follows it!]]
The current code uses 64.