c - What is the maximum number of characters for a host-name in Unix?

Question

I am wondering what is the maximum number of characters for a host-name in a Unix system. In addition is there any defined variable that can be used in Unix programming to call that number? (i.e. number of characters allowed for a host-name).

I am programming in C.

Answer 1

You can usually type:

getconf HOST_NAME_MAX

In addition, you can generally include limits.h to your application and read the value of the define.

While the POSIX standard says it is guaranteed not to exceed 255 bytes, that does not necessarily mean that each implementation will adhere to that.

man gethostname on your platform to get more detailed information.