NAME

gethostname - get host name

SYNOPSIS

#include <unistd.h> int gethostname(char *name, size_t len);

DESCRIPTION

These functions are used to access or to change the host name of the current processor. Note, that on the Internet each interface has a at least one address, and names are associated with addresses, so a machine may (and usually does) have multiple names. gethostname(2) will return the one that the machine identifies itself as.

RETURN VALUE

On success, zero is returned. On error, -1 is returned, and errno is set appropriately.

ERRORS

EINVAL

len is negative or, on Linux/i386, len is smaller than the actual size. (In this last case glibc 2.1 uses ENAMETOOLONG.)

EFAULT

name is an invalid address.

ENAMETOOLONG

len is smaller than the length of the hostname

CONFORMING TO

SVr4, 4.4BSD (this function first appeared in 4.2BSD). POSIX.1 does not define these functions, but ISO/IEC 9945-1:1990 mentions them in B.4.4.1.

BUGS

According to the SUSv2, gethostname(2) must return len bytes (a truncated hostname, NUL-terminated or not) when the hostname is longer. Linux/Alpha (which has a system call gethostname(2)) complies with this requirement, but libc and glibc on Linux/i386 only return an error in this case.

NOTES

The definition of success varies. SUSv2 defines gethostname() as `return possibly truncated hostname', and having a small len does not cause an error return. Of course it must be possible to be certain that one has obtained the full hostname, and to this end SUSv2 guarantees that `Host names are limited to 255 bytes'.

EXAMPLE

1. include <unistd.h>
2. include <malloc.h>
3. include <stdio.h>
4. include <string.h>

int main(int argc,char **argv) {

char domain[256?; int ret=gethostname(domain,sizeof(domain)); if (ret==-1) {

perror("gethostname"); return 1;

} printf("%s\n",domain); return 0;

}

SEE ALSO

getdomainname(2), setdomainname(2), uname(2)