NAME
utmp
, wtmp
,
lastlog
—
login records
SYNOPSIS
#include
<utmp.h>
DESCRIPTION
The file<utmp.h>
declares the
structures used to record information about current users in the file
utmp
, logins and logouts in the file
wtmp
, and last logins in the file
lastlog
. The time stamps of date changes, shutdowns
and reboots are also logged in the wtmp
file.
The wtmp
file can grow rapidly on busy
systems, and is normally rotated with
newsyslog(8).
These files must be created manually; if they do not exist, they are not created automatically.
#define _PATH_UTMP "/var/run/utmp" #define _PATH_WTMP "/var/log/wtmp" #define _PATH_LASTLOG "/var/log/lastlog" #define UT_NAMESIZE 8 #define UT_LINESIZE 8 #define UT_HOSTSIZE 16 struct lastlog { time_t ll_time; char ll_line[UT_LINESIZE]; char ll_host[UT_HOSTSIZE]; }; struct utmp { char ut_line[UT_LINESIZE]; char ut_name[UT_NAMESIZE]; char ut_host[UT_HOSTSIZE]; time_t ut_time; };
Each time a user logs in, the
login(1) program looks up the user's UID in the file
lastlog
. If it is found, the timestamp of the last
time the user logged in, the terminal line and the hostname are written to
the standard output, providing the login is not set
quiet; see
login(1). The
login(1) program then records the new login time in the file
lastlog
.
After the new lastlog record is written, the
file utmp
is opened and the
utmp record for the user inserted. This record remains
there until the user logs out at which time it is deleted (by clearing the
user and host fields, and updating the timestamp field). The
utmp
file is used by the programs
rwho(1), users(1), w(1), and
who(1).
Next, the
login(1) program opens the file wtmp
, and
appends the user's utmp record. When the user logs
out, a utmp record with the tty line, an updated time
stamp, and cleared user and host fields is appended to the file by
init(8). The wtmp
file is used by the
programs last(1) and ac(8).
In the event of a date change, a shutdown or reboot, the following
items are logged in the wtmp
file.
reboot
shutdown
- A system reboot or shutdown has been initiated. The character
‘
~
’ is placed in the field ut_line, andreboot
orshutdown
in the field ut_name (see shutdown(8) and reboot(8)). date
- The system time has been manually or automatically updated by
date(1). The command name date is recorded in the
field ut_name. In the field
ut_line, the character
‘
|
’ indicates the time prior to the change, and the character ‘{
’ indicates the new time.
FILES
- /var/run/utmp
- The
utmp
file. - /var/log/wtmp
- The
wtmp
file. - /var/log/lastlog
- The
lastlog
file.
SEE ALSO
last(1), login(1), w(1), who(1), utmpx(5), ac(8), init(8), lastlogin(8), newsyslog(8)
HISTORY
A utmp
file format appeared in
Version 1 AT&T UNIX. The
wtmp
file format appeared in
Version 3 AT&T UNIX. The
lastlog
file format appeared in
3.0BSD.