SYSCALL(2) BSD Programmer's Manual SYSCALL(2)
syscall, __syscall - indirect system call
syscall(int number, ...);
__syscall(quad_t number, ...);
Syscall() performs the system call whose assembly language interface has
the specified number with the specified arguments. Symbolic constants
for system calls can be found in the header file <sys/syscall.h>. The
__syscall form should be used when one or more of the parameters is a
64-bit argument to ensure that argument alignment is correct. This sys-
tem call is useful for testing new system calls that do not have entries
in the C library.
The return values are defined by the system call being invoked. In gen-
eral, a 0 return value indicates success. A -1 return value indicates an
error, and an error code is stored in errno.
There is no way to simulate system calls that have multiple return values
such as pipe(2).
The syscall function call appeared in 4.0BSD.
4th Berkeley Distribution June 16, 1993 1