usr/share/man/cat5/utmp.0

UTMP(5)                     BSD Programmer's Manual                    UTMP(5)

N\bNA\bAM\bME\bE
     u\but\btm\bmp\bp, w\bwt\btm\bmp\bp, l\bla\bas\bst\btl\blo\bog\bg - login records

S\bSY\bYN\bNO\bOP\bPS\bSI\bIS\bS
     #\b#i\bin\bnc\bcl\blu\bud\bde\be <\b<u\but\btm\bmp\bp.\b.h\bh>\b>

D\bDE\bES\bSC\bCR\bRI\bIP\bPT\bTI\bIO\bON\bN
     The file <_\bu_\bt_\bm_\bp_\b._\bh> declares the structures used to record information
     about current users in the file u\but\btm\bmp\bp, logins and logouts in the file
     w\bwt\btm\bmp\bp, and last logins in the file l\bla\bas\bst\btl\blo\bog\bg. The time stamps of date
     changes, shutdowns and reboots are also logged in the w\bwt\btm\bmp\bp file.

     These files can grow rapidly on busy systems, daily or weekly rotation is
     recommended.  If any of these files do not exist, it is not created.
     These files must be created manually and are normally maintained in ei-
     ther the script _\b/_\be_\bt_\bc_\b/_\bd_\ba_\bi_\bl_\by or the script _\b/_\be_\bt_\bc_\b/_\bw_\be_\be_\bk_\bl_\by. (See cron(8).)

           #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];
                   long    ut_time;
           };

     Each time a user logs in, the login program looks up the user's UID in
     the file l\bla\bas\bst\btl\blo\bog\bg.\b. 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 _\bq_\bu_\bi_\be_\bt, see login(1).)  The login pro-
     gram then records the new login time in the file l\bla\bas\bst\btl\blo\bog\bg.

     After the new _\bl_\ba_\bs_\bt_\bl_\bo_\bg record is written , the file u\but\btm\bmp\bp is opened and the
     _\bu_\bt_\bm_\bp record for the user inserted.  This record remains there until the
     user logs out at which time it is deleted.  The u\but\btm\bmp\bp file is used by the
     programs rwho(1),  users(1),  w(1),  and who(1).

     Next, the login program opens the file w\bwt\btm\bmp\bp, and appends the user's _\bu_\bt_\bm_\bp
     record.  The same _\bu_\bt_\bm_\bp record, with an updated time stamp is later ap-
     pended to the file when the user logs out. (See init(8).)  The w\bwt\btm\bmp\bp 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 w\bwt\btm\bmp\bp file.

     reboot
     shutdown    A system reboot or shutdown has been initiated.  The charac-
                 ter `~' is placed in the field _\bu_\bt_\b__\bl_\bi_\bn_\be, and reboot or
                 shutdown in the field _\bu_\bt_\b__\bn_\ba_\bm_\be. (See shutdown(8) and
                 reboot(8).)


     date        The system time has been manually or automatically updated.
                 (See date(1).)  The command name date is recorded in the
                 field _\bu_\bt_\b__\bn_\ba_\bm_\be. In the field _\bu_\bt_\b__\bl_\bi_\bn_\be, the character `{' indi-
                 cates the time prior to the change, and the character `|' in-
                 dicates the new time.

F\bFI\bIL\bLE\bES\bS
     /var/run/utmp     The u\but\btm\bmp\bp f\bfi\bil\ble\be.\b.
     /var/log/wtmp     The w\bwt\btm\bmp\bp f\bfi\bil\ble\be.\b.
     /var/log/lastlog  The l\bla\bas\bst\btl\blo\bog\bg f\bfi\bil\ble\be.\b.

S\bSE\bEE\bE A\bAL\bLS\bSO\bO
     last(1),  login(1),  who(1),  ac(8),  init(8)

H\bHI\bIS\bST\bTO\bOR\bRY\bY
     A u\but\btm\bmp\bp and w\bwt\btm\bmp\bp file format appeared in Version 6 AT&T UNIX.  The l\bla\bas\bst\btl\blo\bog\bg
     file format appeared in 3.0BSD.

4th Berkeley Distribution        June 5, 1993                                2