LOGIN(3) manual page
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login, logout - write utmp and wtmp entries
#include <utmp.h>
void login(const struct utmp *ut);
int logout(const
char *ut_line);
Link with -lutil.
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 the utmp and the 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 terminal, 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 terminal 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>
Not in POSIX.1-2001. Present on the BSDs.
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>.
getutent(3)
, utmp(5)
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