.Nd substitute user identity
.Sh SYNOPSIS
.Nm
+.Op Fl
.Op Fl flm
-.Op Ar login
-.Op Ar -c shell arguments
+.Op Ar login Op Ar args
.Sh DESCRIPTION
.Nm
requests the password for
.Pp
The options are as follows:
.Bl -tag -width Ds
-.It Fl c
-Invoke the following command in a subshell as the specified user.
.It Fl f
If the invoked shell is
.Xr csh 1 ,