login, logout - write utmp and wtmp entries
void login(const struct utmp
int logout(const char
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
ut, and writes it to both the utmp and the wtmp
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
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
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
fields, updating the
ut_tv timestamp field and setting
ut_type (if there is such a field) to
The logout() function returns 1 if the entry was successfully written to the database, or 0 if an error occurred.
user accounting database, configured through
user accounting log file, configured through
For an explanation of the terms used in this section, see attributes(7).
|Thread safety||MT-Unsafe race:utent
In the above table,
that if any of the functions setutent(3),
getutent(3), or endutent(3) are used
in parallel in different threads of a program, then data races could
occur. login() and logout() calls
those functions, so we use race:utent to remind users.
Not in POSIX.1. Present on the BSDs.
Note that the member
struct utmp is
ut_name in BSD. Therefore,
ut_name is defined
as an alias for
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