login.3

里面包含了telnet的客户端和服务器端

.\" Copyright (c) 1995
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.Dd December 14, 1995
.Dt LOGIN 3
.Os "Linux NetKit (0.17)"
.Sh NAME
.Nm login ,
.Nm logout ,
.Nm logwtmp
.Nd login utility functions
.Sh SYNOPSIS
.Fd #include <util.h>
.Ft void
.Fn login "struct utmp *ut"
.Ft int
.Fn logout "const char *line"
.Ft void
.Fn logwtmp "const char *line" "const char *name" "const char *host"
.Sh DESCRIPTION
The
.Fn login ,
.Fn logout ,
and
.Fn logwtmp
functions operate on the database of current users in
.Pa /var/run/utmp
and on the logfile
.Pa /var/log/wtmp
of logins and logouts.
.Pp
The
.Fn login
function updates the
.Pa /var/run/utmp
and
.Pa /var/log/wtmp
files with user information contained in
.Fa ut .
.Pp
The
.Fn logout
function removes the entry from
.Pa /var/run/utmp
corresponding to the device
.Fa line .
.Pp
The
.Fn logwtmp
function adds an entry to
.Pa /var/log/wtmp .
Since
.Fn login
will add the appropriate entry for
.Pa /var/log/wtmp
during a login,
.Fn logwtmp
is usually used for logouts.
.Sh RETURN VALUES
.Fn logout
returns non-zero if it was able to find and delete an entry for
.Fa line ,
and zero if there is no entry for
.Fa line
in
.Pa /var/run/utmp .
.Sh FILES
.Bl -tag -width /var/run/wtmp -compact
.It Pa /dev/\(**
.It Pa /etc/ttys
.It Pa /var/run/utmp
.It Pa /var/log/wtmp
.El
.Sh SEE ALSO
.Xr utmp 5