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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9 .\" The GNU General Public License's references to "object code"
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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 2021-03-22 "" "Linux Programmer's Manual"
33 getutent, getutid, getutline, pututline, setutent, endutent,
34 utmpname \- access utmp file entries
39 .B struct utmp *getutent(void);
40 .BI "struct utmp *getutid(const struct utmp *" ut );
41 .BI "struct utmp *getutline(const struct utmp *" ut );
43 .BI "struct utmp *pututline(const struct utmp *" ut );
45 .B void setutent(void);
46 .B void endutent(void);
48 .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.
136 On failure, these functions
138 set to indicate the error.
151 functions can also fail for the reasons described in
156 database of currently logged-in users
159 database of past user logins
161 For an explanation of the terms used in this section, see
169 Interface Attribute Value
173 MT-Unsafe init race:utent
174 race:utentbuf sig:ALRM timer
180 MT-Unsafe init race:utent
193 T} Thread safety MT-Unsafe race:utent
202 signifies that if any of the functions
211 are used in parallel in different threads of a program,
212 then data races could occur.
216 In XPG2 and SVID 2 the function
218 is documented to return void, and that is what it does on many systems
220 HP-UX introduces a new function
222 with the prototype given above for
225 All these functions are obsolete now on non-Linux systems.
226 POSIX.1-2001 and POSIX.1-2008, following SUSv1,
227 does not have any of these functions, but instead uses
231 .B #include <utmpx.h>
233 .B struct utmpx *getutxent(void);
234 .B struct utmpx *getutxid(const struct utmpx *);
235 .B struct utmpx *getutxline(const struct utmpx *);
236 .B struct utmpx *pututxline(const struct utmpx *);
237 .B void setutxent(void);
238 .B void endutxent(void);
242 These functions are provided by glibc,
243 and perform the same task as their equivalents without the "x", but use
245 defined on Linux to be the same as
247 For completeness, glibc also provides
249 although this function is not specified by POSIX.1.
251 On some other systems,
252 the \fIutmpx\fP structure is a superset of the \fIutmp\fP structure,
253 with additional fields, and larger versions of the existing fields,
254 and parallel files are maintained, often
259 Linux glibc on the other hand does not use a parallel \fIutmpx\fP file
260 since its \fIutmp\fP structure is already large enough.
261 The "x" functions listed above are just aliases for
262 their counterparts without the "x" (e.g.,
268 The above functions are not thread-safe.
269 Glibc adds reentrant versions
274 .BI "int getutent_r(struct utmp *" ubuf ", struct utmp **" ubufp );
275 .BI "int getutid_r(struct utmp *" ut ,
276 .BI " struct utmp *" ubuf ", struct utmp **" ubufp );
277 .BI "int getutline_r(struct utmp *" ut ,
278 .BI " struct utmp *" ubuf ", struct utmp **" ubufp );
281 Feature Test Macro Requirements for glibc (see
282 .BR feature_test_macros (7)):
289 || /* Since glibc 2.19: */ _DEFAULT_SOURCE
290 || /* Glibc <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
293 These functions are GNU extensions, analogs of the functions of the
294 same name without the _r suffix.
297 argument gives these functions a place to store their result.
298 On success, they return 0, and a pointer to the result is written in
300 On error, these functions return \-1.
301 There are no utmpx equivalents of the above functions.
302 (POSIX.1 does not specify such functions.)
304 The following example adds and removes a utmp record, assuming it is run
305 from within a pseudo terminal.
306 For usage in a real application, you
307 should check the return values of
321 main(int argc, char *argv[])
325 system("echo before adding entry:;who");
327 entry.ut_type = USER_PROCESS;
328 entry.ut_pid = getpid();
329 strcpy(entry.ut_line, ttyname(STDIN_FILENO) + strlen("/dev/"));
330 /* only correct for ptys named /dev/tty[pqr][0\-9a\-z] */
331 strcpy(entry.ut_id, ttyname(STDIN_FILENO) + strlen("/dev/tty"));
332 time(&entry.ut_time);
333 strcpy(entry.ut_user, getpwuid(getuid())\->pw_name);
334 memset(entry.ut_host, 0, UT_HOSTSIZE);
339 system("echo after adding entry:;who");
341 entry.ut_type = DEAD_PROCESS;
342 memset(entry.ut_line, 0, UT_LINESIZE);
344 memset(entry.ut_user, 0, UT_NAMESIZE);
348 system("echo after removing entry:;who");