1GETUTENT(3) Linux Programmer's Manual GETUTENT(3)
2
6 getutent, getutid, getutline, pututline, setutent, endutent, utmpname -
7 access utmp file entries
8
10 #include <utmp.h>
11 struct utmp *getutent(void);
13 struct utmp *getutid(struct utmp *ut);
14 struct utmp *getutline(struct utmp *ut);
15 struct utmp *pututline(struct utmp *ut);
17 void setutent(void);
19 void endutent(void);
20 int utmpname(const char *file);
22
24 New applications should use the POSIX.1-specified "utmpx" versions of
25 these functions; see CONFORMING TO.
26 utmpname() sets the name of the utmp-format file for the other utmp
28 functions to access. If utmpname() is not used to set the filename
29 before the other functions are used, they assume _PATH_UTMP, as defined
30 in <paths.h>.
31 setutent() rewinds the file pointer to the beginning of the utmp file.
33 It is generally a good idea to call it before any of the other func‐
34 tions.
35 endutent() closes the utmp file. It should be called when the user
37 code is done accessing the file with the other functions.
38 getutent() reads a line from the current file position in the utmp
40 file. It returns a pointer to a structure containing the fields of the
41 line. The definition of this structure is shown in utmp(5).
42 getutid() searches forward from the current file position in the utmp
44 file based upon ut. If ut->ut_type is one of RUN_LVL, BOOT_TIME,
45 NEW_TIME, or OLD_TIME, getutid() will find the first entry whose
46 ut_type field matches ut->ut_type. If ut->ut_type is one of
47 INIT_PROCESS, LOGIN_PROCESS, USER_PROCESS, or DEAD_PROCESS, getutid()
48 will find the first entry whose ut_id field matches ut->ut_id.
49 getutline() searches forward from the current file position in the utmp
51 file. It scans entries whose ut_type is USER_PROCESS or LOGIN_PROCESS
52 and returns the first one whose ut_line field matches ut->ut_line.
53 pututline() writes the utmp structure ut into the utmp file. It uses
55 getutid() to search for the proper place in the file to insert the new
56 entry. If it cannot find an appropriate slot for ut, pututline() will
57 append the new entry to the end of the file.
58
60 getutent(), getutid(), and getutline() return a pointer to a struct
61 utmp on success, and NULL on failure (which includes the "record not
62 found" case). This struct utmp is allocated in static storage, and may
63 be overwritten by subsequent calls.
64 On success pututline() returns ut; on failure, it returns NULL.
66 utmpname() returns 0 if the new name was successfully stored, or -1 on
68 failure.
69
71 ENOMEM Out of memory.
72 ESRCH Record not found.
74 setutent(), pututent(), and the getut* () functions can also fail for
76 the reasons described in open(2).
77
79 /var/run/utmp database of currently logged-in users
80 /var/log/wtmp database of past user logins
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83 XPG2, SVr4.
84 In XPG2 and SVID 2 the function pututline() is documented to return
86 void, and that is what it does on many systems (AIX, HP-UX, Linux
87 libc5). HP-UX introduces a new function _pututline() with the proto‐
88 type given above for pututline() (also found in Linux libc5).
89 All these functions are obsolete now on non-Linux systems.
91 POSIX.1-2001, following SUSv1, does not have any of these functions,
92 but instead uses
93 #include <utmpx.h>
95 struct utmpx *getutxent(void);
97 struct utmpx *getutxid(const struct utmpx *);
98 struct utmpx *getutxline(const struct utmpx *);
99 struct utmpx *pututxline(const struct utmpx *);
100 void setutxent(void);
101 void endutxent(void);
102 These functions are provided by glibc, and perform the same task as
104 their equivalents without the "x", but use struct utmpx, defined on
105 Linux to be the same as struct utmp. For completeness, glibc also pro‐
106 vides utmpxname(), although this function is not specified by POSIX.1.
107 On some other systems, the utmpx structure is a superset of the utmp
109 structure, with additional fields, and larger versions of the existing
110 fields, and parallel files are maintained, often /var/*/utmpx and
111 /var/*/wtmpx.
112 Linux glibc on the other hand does not use a parallel utmpx file since
114 its utmp structure is already large enough. The functions getutxent()
115 etc. are aliases for getutent() etc.
116
118 Glibc Notes
119 The above functions are not thread-safe. Glibc adds reentrant versions
120 #define _GNU_SOURCE /* or _SVID_SOURCE or _BSD_SOURCE */
122 #include <utmp.h>
123