2 .\" Copyright 1995 Mark D. Roth (roth@uiuc.edu)
4 .\" SPDX-License-Identifier: GPL-2.0-or-later
6 .\" References consulted:
7 .\" Linux libc source code
10 .\" Modified Thu Jul 25 14:43:46 MET DST 1996 by Michael Haardt
11 .\" <michael@cantor.informatik.rwth-aachen.de>
13 .TH getutent 3 (date) "Linux man-pages (unreleased)"
15 getutent, getutid, getutline, pututline, setutent, endutent,
16 utmpname \- access utmp file entries
19 .RI ( libc ", " \-lc )
24 .B struct utmp *getutent(void);
25 .BI "struct utmp *getutid(const struct utmp *" ut );
26 .BI "struct utmp *getutline(const struct utmp *" ut );
28 .BI "struct utmp *pututline(const struct utmp *" ut );
30 .B void setutent(void);
31 .B void endutent(void);
33 .BI "int utmpname(const char *" file );
36 New applications should use the POSIX.1-specified "utmpx" versions of
37 these functions; see STANDARDS.
40 sets the name of the utmp-format file for the other utmp
44 is not used to set the filename
45 before the other functions are used, they assume \fB_PATH_UTMP\fP, as
46 defined in \fI<paths.h>\fP.
49 rewinds the file pointer to the beginning of the utmp file.
50 It is generally a good idea to call it before any of the other
55 It should be called when the user
56 code is done accessing the file with the other functions.
59 reads a line from the current file position in the utmp file.
60 It returns a pointer to a structure containing the fields of
62 The definition of this structure is shown in
66 searches forward from the current file position in the utmp
67 file based upon \fIut\fP.
68 If \fIut\->ut_type\fP is one of \fBRUN_LVL\fP,
69 \fBBOOT_TIME\fP, \fBNEW_TIME\fP, or \fBOLD_TIME\fP,
72 find the first entry whose \fIut_type\fP field matches \fIut\->ut_type\fP.
73 If \fIut\->ut_type\fP is one of \fBINIT_PROCESS\fP, \fBLOGIN_PROCESS\fP,
74 \fBUSER_PROCESS\fP, or \fBDEAD_PROCESS\fP,
79 field matches \fIut\->ut_id\fP.
82 searches forward from the current file position in the utmp file.
83 It scans entries whose
86 or \fBLOGIN_PROCESS\fP and returns the first one whose
89 matches \fIut\->ut_line\fP.
94 structure \fIut\fP into the utmp file.
97 to search for the proper place in the file to insert
99 If it cannot find an appropriate slot for \fIut\fP,
101 will append the new entry to the end of the file.
107 return a pointer to a \fIstruct utmp\fP on success,
108 and NULL on failure (which includes the "record not found" case).
109 This \fIstruct utmp\fP is allocated in static storage, and may be
110 overwritten by subsequent calls.
116 on failure, it returns NULL.
119 returns 0 if the new name was successfully stored, or \-1 on failure.
121 On failure, these functions
123 set to indicate the error.
136 functions can also fail for the reasons described in
141 database of currently logged-in users
144 database of past user logins
146 For an explanation of the terms used in this section, see
154 Interface Attribute Value
158 MT-Unsafe init race:utent
159 race:utentbuf sig:ALRM timer
165 MT-Unsafe init race:utent
178 T} Thread safety MT-Unsafe race:utent
187 signifies that if any of the functions
196 are used in parallel in different threads of a program,
197 then data races could occur.
201 In XPG2 and SVID 2 the function
203 is documented to return void, and that is what it does on many systems
205 HP-UX introduces a new function
207 with the prototype given above for
210 All these functions are obsolete now on non-Linux systems.
211 POSIX.1-2001 and POSIX.1-2008, following SUSv1,
212 does not have any of these functions, but instead uses
216 .B #include <utmpx.h>
218 .B struct utmpx *getutxent(void);
219 .B struct utmpx *getutxid(const struct utmpx *);
220 .B struct utmpx *getutxline(const struct utmpx *);
221 .B struct utmpx *pututxline(const struct utmpx *);
222 .B void setutxent(void);
223 .B void endutxent(void);
227 These functions are provided by glibc,
228 and perform the same task as their equivalents without the "x", but use
230 defined on Linux to be the same as
232 For completeness, glibc also provides
234 although this function is not specified by POSIX.1.
236 On some other systems,
237 the \fIutmpx\fP structure is a superset of the \fIutmp\fP structure,
238 with additional fields, and larger versions of the existing fields,
239 and parallel files are maintained, often
244 Linux glibc on the other hand does not use a parallel \fIutmpx\fP file
245 since its \fIutmp\fP structure is already large enough.
246 The "x" functions listed above are just aliases for
247 their counterparts without the "x" (e.g.,
253 The above functions are not thread-safe.
254 glibc adds reentrant versions
259 .BI "int getutent_r(struct utmp *" ubuf ", struct utmp **" ubufp );
260 .BI "int getutid_r(struct utmp *" ut ,
261 .BI " struct utmp *" ubuf ", struct utmp **" ubufp );
262 .BI "int getutline_r(struct utmp *" ut ,
263 .BI " struct utmp *" ubuf ", struct utmp **" ubufp );
266 Feature Test Macro Requirements for glibc (see
267 .BR feature_test_macros (7)):
274 || /* Since glibc 2.19: */ _DEFAULT_SOURCE
275 || /* glibc <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
278 These functions are GNU extensions, analogs of the functions of the
279 same name without the _r suffix.
282 argument gives these functions a place to store their result.
283 On success, they return 0, and a pointer to the result is written in
285 On error, these functions return \-1.
286 There are no utmpx equivalents of the above functions.
287 (POSIX.1 does not specify such functions.)
289 The following example adds and removes a utmp record, assuming it is run
290 from within a pseudo terminal.
291 For usage in a real application, you
292 should check the return values of
297 .\" SRC BEGIN (getutent.c)
311 system("echo before adding entry:;who");
313 entry.ut_type = USER_PROCESS;
314 entry.ut_pid = getpid();
315 strcpy(entry.ut_line, ttyname(STDIN_FILENO) + strlen("/dev/"));
316 /* only correct for ptys named /dev/tty[pqr][0\-9a\-z] */
317 strcpy(entry.ut_id, ttyname(STDIN_FILENO) + strlen("/dev/tty"));
318 time(&entry.ut_time);
319 strcpy(entry.ut_user, getpwuid(getuid())\->pw_name);
320 memset(entry.ut_host, 0, UT_HOSTSIZE);
325 system("echo after adding entry:;who");
327 entry.ut_type = DEAD_PROCESS;
328 memset(entry.ut_line, 0, UT_LINESIZE);
330 memset(entry.ut_user, 0, UT_NAMESIZE);
334 system("echo after removing entry:;who");