login, logout — write utmp and wtmp entries
#include <utmp.h>
void
login( |
const struct utmp * | ut) ; |
int
logout( |
const char * | ut_line) ; |
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The utmp file records who is currently using the system. The wtmp file records all logins and logouts. See utmp(5).
The function login
() takes
the supplied struct
utmp, ut
,
and writes it to both utmp and wtmp file.
The function logout
() clears
the entry in the utmp file again.
More precisely, login
()
takes the argument ut
struct, fills the field
ut->ut_type
(if there is such a field) with the value USER_PROCESS
, and fills the field
ut->ut_pid
(if
there is such a field) with the process ID of the calling
process. Then it tries to fill the field ut->ut_line
. It takes
the first of stdin
,
stdout
, stderr
that is a tty, and stores the
corresponding pathname minus a possible leading
/dev/
into this field, and
then writes the struct to the utmp file. On the other hand,
if no tty name was found, this field is filled with "???"
and the struct is not written to the utmp file. After this,
the struct is written to the wtmp file.
The logout
() function
searches the utmp file for an entry matching the ut_line
argument. If a record
is found, it is updated by zeroing out the ut_name
and ut_host
fields, updating
the ut_tv
timestamp field and setting ut_type
(if there is such a
field) to DEAD_PROCESS
.
The logout
() function
returns 1 if the entry was successfully written to the
database, or 0 if an error occurred.
/var/run/utmp
user accounting database, configured through
_PATH_UTMP
in <paths.h>
/var/log/wtmp
user accounting log file, configured through
_PATH_WTMP
in <paths.h>
Note that the member ut_user
of struct utmp is called ut_name
in BSD. Therefore,
ut_name
is defined
as an alias for ut_user
in <utmp.h>
.
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