ether_aton, ether_ntoa, ether_ntohost, ether_hostton, ether_line, ether_ntoa_r, ether_aton_r − Ethernet address manipulation routines


#include <netinet/ether.h>

char *ether_ntoa(const struct ether_addr *addr);

struct ether_addr *ether_aton(const char *asc);

int ether_ntohost(char *hostname, const struct ether_addr *addr);

int ether_hostton(const char *hostname, struct ether_addr *addr);

int ether_line(const char *line, struct ether_addr *addr,
char *

/* GNU extensions */
char *ether_ntoa_r(const struct ether_addr *
addr, char *buf);

struct ether_addr *ether_aton_r(const char *asc,
struct ether_addr *


ether_aton() converts the 48-bit Ethernet host address asc from the standard hex-digits-and-colons notation into binary data in network byte order and returns a pointer to it in a statically allocated buffer, which subsequent calls will overwrite. ether_aton() returns NULL if the address is invalid.

The ether_ntoa() function converts the Ethernet host address addr given in network byte order to a string in standard hex-digits-and-colons notation, omitting leading zeros. The string is returned in a statically allocated buffer, which subsequent calls will overwrite.

The ether_ntohost() function maps an Ethernet address to the corresponding hostname in /etc/ethers and returns nonzero if it cannot be found.

The ether_hostton() function maps a hostname to the corresponding Ethernet address in /etc/ethers and returns nonzero if it cannot be found.

The ether_line() function parses a line in /etc/ethers format (ethernet address followed by whitespace followed by hostname; '#' introduces a comment) and returns an address and hostname pair, or nonzero if it cannot be parsed. The buffer pointed to by hostname must be sufficiently long, for example, have the same length as line.

The functions ether_ntoa_r() and ether_aton_r() are reentrant thread-safe versions of ether_ntoa() and ether_aton() respectively, and do not use static buffers.

The structure ether_addr is defined in <net/ethernet.h> as:

struct ether_addr {
uint8_t ether_addr_octet[6];


Multithreading (see pthreads(7))
The ether_aton() and ether_ntoa() functions are not thread-safe.

The ether_ntohost(), ether_hostton(), ether_line(), ether_ntoa_r() and ether_aton_r() functions are thread-safe.


4.3BSD, SunOS.


The glibc 2.2.5 implementation of ether_line() is broken.




This page is part of release 3.69 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at−pages/.


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.