1GETUTENT(3)                Linux Programmer's Manual               GETUTENT(3)
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NAME

6       getutent, getutid, getutline, pututline, setutent, endutent, utmpname -
7       access utmp file entries
8

SYNOPSIS

10       #include <utmp.h>
11
12       struct utmp *getutent(void);
13       struct utmp *getutid(struct utmp *ut);
14       struct utmp *getutline(struct utmp *ut);
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16       struct utmp *pututline(struct utmp *ut);
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18       void setutent(void);
19       void endutent(void);
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21       int utmpname(const char *file);
22

DESCRIPTION

24       New applications should use the POSIX.1-specified "utmpx"  versions  of
25       these functions; see CONFORMING TO.
26
27       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
32       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
36       endutent() closes the utmp file.  It should be  called  when  the  user
37       code is done accessing the file with the other functions.
38
39       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
43       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
50       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.
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54       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.
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RETURN VALUE

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.
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65       On success pututline() returns ut; on failure, it returns NULL.
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67       utmpname() returns 0 if the new name was successfully stored, or -1  on
68       failure.
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70       In  the  event  of  an error, these functions errno set to indicate the
71       cause.
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ERRORS

74       ENOMEM Out of memory.
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76       ESRCH  Record not found.
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78       setutent(), pututline(), and the getut* () functions can also fail  for
79       the reasons described in open(2).
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FILES

82       /var/run/utmp  database of currently logged-in users
83       /var/log/wtmp  database of past user logins
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CONFORMING TO

86       XPG2, SVr4.
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88       In  XPG2  and  SVID  2 the function pututline() is documented to return
89       void, and that is what it does  on  many  systems  (AIX,  HP-UX,  Linux
90       libc5).   HP-UX  introduces a new function _pututline() with the proto‐
91       type given above for pututline() (also found in Linux libc5).
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93       All  these  functions  are   obsolete   now   on   non-Linux   systems.
94       POSIX.1-2001,  following  SUSv1,  does not have any of these functions,
95       but instead uses
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97       #include <utmpx.h>
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99       struct utmpx *getutxent(void);
100       struct utmpx *getutxid(const struct utmpx *);
101       struct utmpx *getutxline(const struct utmpx *);
102       struct utmpx *pututxline(const struct utmpx *);
103       void setutxent(void);
104       void endutxent(void);
105
106       These functions are provided by glibc, and perform  the  same  task  as
107       their  equivalents  without  the  "x", but use struct utmpx, defined on
108       Linux to be the same as struct utmp.  For completeness, glibc also pro‐
109       vides utmpxname(), although this function is not specified by POSIX.1.
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111       On  some  other  systems, the utmpx structure is a superset of the utmp
112       structure, with additional fields, and larger versions of the  existing
113       fields,  and  parallel  files  are  maintained,  often /var/*/utmpx and
114       /var/*/wtmpx.
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116       Linux glibc on the other hand does not use a parallel utmpx file  since
117       its  utmp  structure is already large enough.  The "x" functions listed
118       above are just aliases for their counterparts without  the  "x"  (e.g.,
119       getutxent() is an alias for getutent()).
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NOTES

122   Glibc notes
123       The above functions are not thread-safe.  Glibc adds reentrant versions
124
125       #define _GNU_SOURCE    /* or _SVID_SOURCE or _BSD_SOURCE;
126                                 see feature_test_macros(7) */
127       #include <utmp.h>
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129       int getutent_r(struct utmp *ubuf, struct utmp **ubufp);
130
131       int getutid_r(struct utmp *ut,
132                     struct utmp *ubuf, struct utmp **ubufp);
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134       int getutline_r(struct utmp *ut,
135                       struct utmp *ubuf, struct utmp **ubufp);
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137       These  functions  are  GNU  extensions, analogs of the functions of the
138       same name without the _r suffix.  The ubuf argument gives  these  func‐
139       tions  a  place to store their result.  On success they return 0, and a
140       pointer to the result is written in *ubufp.  On error  these  functions
141       return  -1.   There  are  no  utmpx equivalents of the above functions.
142       (POSIX.1 does not specify such functions.)
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EXAMPLE

145       The following example adds and removes a utmp record,  assuming  it  is
146       run  from  within  a pseudo terminal.  For usage in a real application,
147       you should check the return values of getpwuid(3) and ttyname(3).
148
149       #include <string.h>
150       #include <stdlib.h>
151       #include <pwd.h>
152       #include <unistd.h>
153       #include <utmp.h>
154
155       int
156       main(int argc, char *argv[])
157       {
158           struct utmp entry;
159
160           system("echo before adding entry:;who");
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162           entry.ut_type = USER_PROCESS;
163           entry.ut_pid = getpid();
164           strcpy(entry.ut_line, ttyname(STDIN_FILENO) + strlen("/dev/"));
165           /* only correct for ptys named /dev/tty[pqr][0-9a-z] */
166           strcpy(entry.ut_id, ttyname(STDIN_FILENO) + strlen("/dev/tty"));
167           time(&entry.ut_time);
168           strcpy(entry.ut_user, getpwuid(getuid())->pw_name);
169           memset(entry.ut_host, 0, UT_HOSTSIZE);
170           entry.ut_addr = 0;
171           setutent();
172           pututline(&entry);
173
174           system("echo after adding entry:;who");
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176           entry.ut_type = DEAD_PROCESS;
177           memset(entry.ut_line, 0, UT_LINESIZE);
178           entry.ut_time = 0;
179           memset(entry.ut_user, 0, UT_NAMESIZE);
180           setutent();
181           pututline(&entry);
182
183           system("echo after removing entry:;who");
184
185           endutent();
186           exit(EXIT_SUCCESS);
187       }
188

SEE ALSO

190       getutmp(3), utmp(5)
191

COLOPHON

193       This page is part of release 3.53 of the Linux  man-pages  project.   A
194       description  of  the project, and information about reporting bugs, can
195       be found at http://www.kernel.org/doc/man-pages/.
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199                                  2013-04-19                       GETUTENT(3)
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