Originální popis anglicky:
login, logout - write utmp and wtmp entries
Návod, kniha: Linux System Administration
#include <utmp.h>
void login(const struct utmp *ut);
int logout(const char *ut_line);
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.
These functions are included in libutil, hence you'll need to add
-lutil
to your compiler commandline.
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.
- /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>
getutent(3),
utmp(5)
