How can I get my hostname within a function?

Question

the unix hostname program gives me an exceedingly simple way to get my "real" hostname (not localhost. For example, for me it's currently unknown74e5[...]df7.att.net ). But how can I do this inside of my own code with C system calls? I'd like to get a char * that has this string in it so that I can pass it into gethostbyname and similar.

While I'm at it, I'd like also to know how I can get my IP address with UNIX system calls rather than relying on programs (or worse, whatismyip.com)...

Thanks!

Answer 1

gethostname(2)是POSIX强制的C库函数，为hostname程序提供动力：

   int gethostname(char *name, size_t len);

Answer 2

You can use uname(2) which gets you a struct utsname filled with information. You're interested in nodename

struct utsname {
    char sysname[];    /* Operating system name (e.g., "Linux") */
    char nodename[];   /* Name within "some implementation-defined network". */

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The uname function and utsname struct are also mentioned by POSIX and available on virtually all platforms. As Thomas mentions in the comments, glibc implements gethostname as a call to uname(2) .