1 .\" Copyright 1995 Mark D. Roth (roth@uiuc.edu)
3 .\" %%%LICENSE_START(GPLv2+_DOC_FULL)
4 .\" This is free documentation; you can redistribute it and/or
5 .\" modify it under the terms of the GNU General Public License as
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16 .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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19 .\" You should have received a copy of the GNU General Public
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24 .\" References consulted:
25 .\" Linux libc source code
28 .\" Modified Thu Jul 25 14:43:46 MET DST 1996 by Michael Haardt
29 .\" <michael@cantor.informatik.rwth-aachen.de>
31 .TH GETUTENT 3 2014-08-19 "" "Linux Programmer's Manual"
33 getutent, getutid, getutline, pututline, setutent, endutent,
34 utmpname \- access utmp file entries
38 .B struct utmp *getutent(void);
40 .BI "struct utmp *getutid(const struct utmp *" ut );
42 .BI "struct utmp *getutline(const struct utmp *" ut );
44 .BI "struct utmp *pututline(const struct utmp *" ut );
46 .B void setutent(void);
48 .B void endutent(void);
50 .BI "int utmpname(const char *" file );
52 New applications should use the POSIX.1-specified "utmpx" versions of
53 these functions; see CONFORMING TO.
56 sets the name of the utmp-format file for the other utmp
60 is not used to set the filename
61 before the other functions are used, they assume \fB_PATH_UTMP\fP, as
62 defined in \fI<paths.h>\fP.
65 rewinds the file pointer to the beginning of the utmp file.
66 It is generally a good idea to call it before any of the other
71 It should be called when the user
72 code is done accessing the file with the other functions.
75 reads a line from the current file position in the utmp file.
76 It returns a pointer to a structure containing the fields of
78 The definition of this structure is shown in
82 searches forward from the current file position in the utmp
83 file based upon \fIut\fP.
84 If \fIut\->ut_type\fP is one of \fBRUN_LVL\fP,
85 \fBBOOT_TIME\fP, \fBNEW_TIME\fP, or \fBOLD_TIME\fP,
88 find the first entry whose \fIut_type\fP field matches \fIut\->ut_type\fP.
89 If \fIut\->ut_type\fP is one of \fBINIT_PROCESS\fP, \fBLOGIN_PROCESS\fP,
90 \fBUSER_PROCESS\fP, or \fBDEAD_PROCESS\fP,
95 field matches \fIut\->ut_id\fP.
98 searches forward from the current file position in the utmp file.
99 It scans entries whose
101 is \fBUSER_PROCESS\fP
102 or \fBLOGIN_PROCESS\fP and returns the first one whose
105 matches \fIut\->ut_line\fP.
110 structure \fIut\fP into the utmp file.
113 to search for the proper place in the file to insert
115 If it cannot find an appropriate slot for \fIut\fP,
117 will append the new entry to the end of the file.
123 return a pointer to a \fIstruct utmp\fP on success,
124 and NULL on failure (which includes the "record not found" case).
125 This \fIstruct utmp\fP is allocated in static storage, and may be
126 overwritten by subsequent calls.
132 on failure, it returns NULL.
135 returns 0 if the new name was successfully stored, or \-1 on failure.
137 In the event of an error, these functions
139 set to indicate the cause.
152 functions can also fail for the reasons described in
155 /var/run/utmp database of currently logged-in users
157 /var/log/wtmp database of past user logins
161 In XPG2 and SVID 2 the function
163 is documented to return void, and that is what it does on many systems
165 HP-UX introduces a new function
167 with the prototype given above for
170 All these functions are obsolete now on non-Linux systems.
171 POSIX.1-2001, following SUSv1,
172 does not have any of these functions, but instead uses
174 .B #include <utmpx.h>
176 .B struct utmpx *getutxent(void);
178 .B struct utmpx *getutxid(const struct utmpx *);
180 .B struct utmpx *getutxline(const struct utmpx *);
182 .B struct utmpx *pututxline(const struct utmpx *);
184 .B void setutxent(void);
186 .B void endutxent(void);
188 These functions are provided by glibc,
189 and perform the same task as their equivalents without the "x", but use
191 defined on Linux to be the same as
193 For completeness, glibc also provides
195 although this function is not specified by POSIX.1.
197 On some other systems,
198 the \fIutmpx\fP structure is a superset of the \fIutmp\fP structure,
199 with additional fields, and larger versions of the existing fields,
200 and parallel files are maintained, often
205 Linux glibc on the other hand does not use a parallel \fIutmpx\fP file
206 since its \fIutmp\fP structure is already large enough.
207 The "x" functions listed above are just aliases for
208 their counterparts without the "x" (e.g.,
214 The above functions are not thread-safe.
215 Glibc adds reentrant versions
218 .BR "#define _GNU_SOURCE" " /* or _SVID_SOURCE or _BSD_SOURCE;
219 .RB "\& see " feature_test_macros "(7) */"
222 .BI "int getutent_r(struct utmp *" ubuf ", struct utmp **" ubufp );
224 .BI "int getutid_r(struct utmp *" ut ,
225 .BI " struct utmp *" ubuf ", struct utmp **" ubufp );
227 .BI "int getutline_r(struct utmp *" ut ,
228 .BI " struct utmp *" ubuf ", struct utmp **" ubufp );
231 These functions are GNU extensions, analogs of the functions of the
232 same name without the _r suffix.
235 argument gives these functions a place to store their result.
236 On success they return 0, and a pointer to the result is written in
238 On error, these functions return \-1.
239 There are no utmpx equivalents of the above functions.
240 (POSIX.1 does not specify such functions.)
242 The following example adds and removes a utmp record, assuming it is run
243 from within a pseudo terminal.
244 For usage in a real application, you
245 should check the return values of
258 main(int argc, char *argv[])
262 system("echo before adding entry:;who");
264 entry.ut_type = USER_PROCESS;
265 entry.ut_pid = getpid();
266 strcpy(entry.ut_line, ttyname(STDIN_FILENO) + strlen("/dev/"));
267 /* only correct for ptys named /dev/tty[pqr][0\-9a\-z] */
268 strcpy(entry.ut_id, ttyname(STDIN_FILENO) + strlen("/dev/tty"));
269 time(&entry.ut_time);
270 strcpy(entry.ut_user, getpwuid(getuid())\->pw_name);
271 memset(entry.ut_host, 0, UT_HOSTSIZE);
276 system("echo after adding entry:;who");
278 entry.ut_type = DEAD_PROCESS;
279 memset(entry.ut_line, 0, UT_LINESIZE);
281 memset(entry.ut_user, 0, UT_NAMESIZE);
285 system("echo after removing entry:;who");
295 This page is part of release 3.79 of the Linux
298 A description of the project,
299 information about reporting bugs,
300 and the latest version of this page,
302 \%http://www.kernel.org/doc/man\-pages/.