LOGIN(3) | Library Functions Manual | LOGIN(3)

# NAME

`login`, `logout`, `logwtmp` — login utility functions

# SYNOPSIS

System Utilities Library (libutil, -lutil)
`#include <utmp.h>`
`#include <util.h>`

void
`login`(struct utmp *ut);

int
`logout`(const char *line);

void
`logwtmp`(const char *line, const char *name, const char *host);

# DESCRIPTION

The `login`(), `logout`(), and `logwtmp`() functions operate on the database of current users in /var/run/utmp and on the logfile /var/log/wtmp of logins and logouts.

The `login`() function updates the /var/run/utmp and /var/log/wtmp files with user information contained in ut.

The `logout`() function removes the entry from /var/run/utmp corresponding to the device line.

The `logwtmp`() function adds an entry to /var/log/wtmp. Since `login`() will add the appropriate entry for /var/log/wtmp during a login, `logwtmp`() is usually used for logouts.

# RETURN VALUES

`logout`() returns non-zero if it was able to find and delete an entry for line, and zero if there is no entry for line in /var/run/utmp.

# FILES

/dev/∗
/etc/ttys
/var/run/utmp
/var/log/wtmp

# SEE ALSO

utmp(5)

June 6, 2025 | Debian