1 .\" Hey Emacs! This file is -*- nroff -*- source.
3 .\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu)
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25 .\" Modified 1995-07-22 by Michael Chastain <mec@duracef.shout.net>:
26 .\" 'gethostname' is real system call on Linux/Alpha.
27 .\" Modified 1997-01-31 by Eric S. Raymond <esr@thyrsus.com>
28 .\" Modified 2000-06-04, 2001-12-15 by aeb
29 .\" Modified 2004-06-17 by mtk
30 .\" Modified 2008-11-27 by mtk
32 .TH GETHOSTNAME 2 2008-11-27 "Linux" "Linux Programmer's Manual"
34 gethostname, sethostname \- get/set hostname
36 .B #include <unistd.h>
38 .BI "int gethostname(char *" name ", size_t " len );
40 .BI "int sethostname(const char *" name ", size_t " len );
43 Feature Test Macro Requirements for glibc (see
44 .BR feature_test_macros (7)):
49 _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500
52 _BSD_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE\ <\ 500)
55 These system calls are used to access or to change the hostname of the
59 sets the hostname to the value given in the character array
63 argument specifies the number of bytes in
67 does not require a terminating null byte.)
70 returns the null-terminated hostname in the character array
75 If the null-terminated hostname is too large to fit,
76 then the name is truncated, and no error is returned (but see NOTES below).
77 POSIX.1-2001 says that if such truncation occurs,
78 then it is unspecified whether the returned buffer
79 includes a terminating null byte.
81 On success, zero is returned.
82 On error, \-1 is returned, and
89 is an invalid address.
94 .\" Can't occur for gethostbyname() wrapper, since 'len' has an
95 .\" unsigned type; can occur for the underlying system call.
99 is larger than the maximum allowed size.
102 .RB "(glibc " gethostname ())
104 is smaller than the actual size.
105 (Before version 2.1, glibc uses
112 the caller did not have the
116 SVr4, 4.4BSD (these interfaces first appeared in 4.2BSD).
117 POSIX.1-2001 specifies
122 SUSv2 guarantees that "Host names are limited to 255 bytes".
123 POSIX.1-2001 guarantees that "Host names (not including
124 the terminating null byte) are limited to
129 is defined with the value 64, which has been the limit since Linux 1.0
130 (earlier kernels imposed a limit of 8 bytes).
132 The GNU C library does not employ the
134 system call; instead, it implements
136 as a library function that calls
140 bytes from the returned
144 Having performed the copy, the function then checks if the length of the
146 was greater than or equal to
148 and if it is, then the function returns \-1 with
152 in this case, no null-terminator is included in the returned
155 Versions of glibc before 2.2
156 .\" At least glibc 2.0 and 2.1, older versions not checked
157 handle the case where the length of the
159 was greater than or equal to
161 differently: nothing is copied into
163 and the function returns \-1 with
168 .BR getdomainname (2),
169 .BR setdomainname (2),