1 .\" Copyright 1995 Mark D. Roth (roth@uiuc.edu)
3 .\" This is free documentation; you can redistribute it and/or
4 .\" modify it under the terms of the GNU General Public License as
5 .\" published by the Free Software Foundation; either version 2 of
6 .\" the License, or (at your option) any later version.
8 .\" The GNU General Public License's references to "object code"
9 .\" and "executables" are to be interpreted as the output of any
10 .\" document formatting or typesetting system, including
11 .\" intermediate and printed output.
13 .\" This manual is distributed in the hope that it will be useful,
14 .\" but WITHOUT ANY WARRANTY; without even the implied warranty of
15 .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 .\" GNU General Public License for more details.
18 .\" You should have received a copy of the GNU General Public
19 .\" License along with this manual; if not, write to the Free
20 .\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
23 .\" References consulted:
24 .\" Linux libc source code
27 .\" Modified Thu Jul 25 14:43:46 MET DST 1996 by Michael Haardt
28 .\" <michael@cantor.informatik.rwth-aachen.de>
30 .TH GETUTENT 3 2008-06-29 "" "Linux Programmer's Manual"
32 getutent, getutid, getutline, pututline, setutent, endutent,
33 utmpname \- access utmp file entries
37 .B struct utmp *getutent(void);
39 .BI "struct utmp *getutid(struct utmp *" ut );
41 .BI "struct utmp *getutline(struct utmp *" ut );
43 .BI "struct utmp *pututline(struct utmp *" ut );
45 .B void setutent(void);
47 .B void endutent(void);
49 .BI "int utmpname(const char *" file );
51 New applications should use the POSIX.1-specified "utmpx" versions of
52 these functions; see CONFORMING TO.
55 sets the name of the utmp-format file for the other utmp
59 is not used to set the filename
60 before the other functions are used, they assume \fB_PATH_UTMP\fP, as
61 defined in \fI<paths.h>\fP.
64 rewinds the file pointer to the beginning of the utmp file.
65 It is generally a good idea to call it before any of the other
70 It should be called when the user
71 code is done accessing the file with the other functions.
74 reads a line from the current file position in the utmp file.
75 It returns a pointer to a structure containing the fields of
77 The definition of this structure is shown in
81 searches forward from the current file position in the utmp
82 file based upon \fIut\fP.
83 If \fIut\->ut_type\fP is one of \fBRUN_LVL\fP,
84 \fBBOOT_TIME\fP, \fBNEW_TIME\fP, or \fBOLD_TIME\fP,
87 find the first entry whose \fIut_type\fP field matches \fIut\->ut_type\fP.
88 If \fIut\->ut_type\fP is one of \fBINIT_PROCESS\fP, \fBLOGIN_PROCESS\fP,
89 \fBUSER_PROCESS\fP, or \fBDEAD_PROCESS\fP,
94 field matches \fIut\->ut_id\fP.
97 searches forward from the current file position in the utmp file.
98 It scans entries whose
100 is \fBUSER_PROCESS\fP
101 or \fBLOGIN_PROCESS\fP and returns the first one whose
104 matches \fIut\->ut_line\fP.
109 structure \fIut\fP into the utmp file.
112 to search for the proper place in the file to insert
114 If it cannot find an appropriate slot for \fIut\fP,
116 will append the new entry to the end of the file.
122 return a pointer to a \fIstruct utmp\fP on success,
123 and NULL on failure (which includes the "record not found" case).
124 This \fIstruct utmp\fP is allocated in static storage, and may be
125 overwritten by subsequent calls.
131 on failure, it returns NULL.
134 returns 0 if the new name was successfully stored, or \-1 on failure.
147 functions can also fail for the reasons described in
150 /var/run/utmp database of currently logged-in users
152 /var/log/wtmp database of past user logins
156 In XPG2 and SVID 2 the function
158 is documented to return void, and that is what it does on many systems
159 (AIX, HP-UX, Linux libc5).
160 HP-UX introduces a new function
162 with the prototype given above for
164 (also found in Linux libc5).
166 All these functions are obsolete now on non-Linux systems.
167 POSIX.1-2001, following SUSv1,
168 does not have any of these functions, but instead uses
170 .B #include <utmpx.h>
172 .B struct utmpx *getutxent(void);
174 .B struct utmpx *getutxid(const struct utmpx *);
176 .B struct utmpx *getutxline(const struct utmpx *);
178 .B struct utmpx *pututxline(const struct utmpx *);
180 .B void setutxent(void);
182 .B void endutxent(void);
184 These functions are provided by glibc,
185 and perform the same task as their equivalents without the "x", but use
187 defined on Linux to be the same as
189 For completeness, glibc also provides
191 although this function is not specified by POSIX.1.
193 On some other systems,
194 the \fIutmpx\fP structure is a superset of the \fIutmp\fP structure,
195 with additional fields, and larger versions of the existing fields,
196 and parallel files are maintained, often
201 Linux glibc on the other hand does not use a parallel \fIutmpx\fP file
202 since its \fIutmp\fP structure is already large enough.
203 The "x" functions listed above are just aliases for
204 their counterparts without the "x" (e.g.,
210 The above functions are not thread-safe.
211 Glibc adds reentrant versions
214 .BR "#define _GNU_SOURCE" " /* or _SVID_SOURCE or _BSD_SOURCE;
215 .RB "\& see " feature_test_macros(7) " */"
218 .BI "int getutent_r(struct utmp *" ubuf ", struct utmp **" ubufp );
220 .BI "int getutid_r(struct utmp *" ut ,
221 .BI " struct utmp *" ubuf ", struct utmp **" ubufp );
223 .BI "int getutline_r(struct utmp *" ut ,
224 .BI " struct utmp *" ubuf ", struct utmp **" ubufp );
227 These functions are GNU extensions, analogs of the functions of the
228 same name without the _r suffix.
231 argument gives these functions a place to store their result.
232 On success they return 0, and a pointer to the result is written in
234 On error these functions return \-1.
235 There are no utmpx equivalents of the above functions.
236 (POSIX.1 does not specify such functions.)
238 The following example adds and removes a utmp record, assuming it is run
239 from within a pseudo terminal.
240 For usage in a real application, you
241 should check the return values of
254 main(int argc, char *argv[])
258 system("echo before adding entry:;who");
260 entry.ut_type = USER_PROCESS;
261 entry.ut_pid = getpid();
262 strcpy(entry.ut_line, ttyname(STDIN_FILENO) + strlen("/dev/"));
263 /* only correct for ptys named /dev/tty[pqr][0\-9a\-z] */
264 strcpy(entry.ut_id, ttyname(STDIN_FILENO) + strlen("/dev/tty"));
265 time(&entry.ut_time);
266 strcpy(entry.ut_user, getpwuid(getuid())\->pw_name);
267 memset(entry.ut_host, 0, UT_HOSTSIZE);
272 system("echo after adding entry:;who");
274 entry.ut_type = DEAD_PROCESS;
275 memset(entry.ut_line, 0, UT_LINESIZE);
277 memset(entry.ut_user, 0, UT_NAMESIZE);
281 system("echo after removing entry:;who");