bsd man page for syscall

SYSCALL(2)							System Calls Manual							SYSCALL(2)

NAME
       syscall - indirect system call

SYNOPSIS
       #include <syscall.h>

       syscall(number, arg, ...)  (VAX-11)

DESCRIPTION
       Syscall performs the system call whose assembly language interface has the specified number, register arguments r0 and r1 and further argu-
       ments arg.  Symbolic constants for system calls can be found in the header file <syscall.h>.

       The r0 value of the system call is returned.

DIAGNOSTICS
       When the C-bit is set, syscall returns -1 and sets the external variable errno (see intro(2)).

BUGS
       There is no way to simulate system calls such as pipe(2), which return values in register r1.

4th Berkeley Distribution					  April 16, 1986							SYSCALL(2)