+.Sh LEGACY SYNOPSIS
+.Fd #include <unistd.h>
+.Pp
+.Ft int
+.br
+.Fo setpgrp
+.Fa "pid_t pid"
+.Fa "pid_t pgid"
+.Fc ;
+.Pp
+The legacy
+.Fn setpgrp
+function is a clone of the
+.Fn setpgid
+function, retained for calling convention compatibility
+with historical versions of
+.Bx .
+.Sh COMPATIBILITY
+Use of the legacy version of the
+.Fn setpgrp
+call will cause compiler diagnostics.
+Use
+.Fn setpgid
+instead.
+.Pp
+Use of private (and conflicting) prototypes for
+.Fn setpgrp
+will cause compiler diagnostics.
+Delete the private prototypes and include
+.In unistd.h .