SYSCALL(2) BSD Programmer's Manual SYSCALL(2)NAME
syscall, __syscall - indirect system call
SYNOPSIS
#include <sys/syscall.h>
#include <unistd.h>
int
syscall(int number, ...);
__syscall(quad_t number, ...);
DESCRIPTIONsyscall() 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>.
Since different system calls have different return types, a prototype of
__syscall specifying the correct return type should be declared locally.
This is especially important for system calls returning larger-than-int
results.
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 system
call is useful for testing new system calls that do not have entries in
the C library.
RETURN VALUES
The return values are defined by the system call being invoked. In gen-
eral, for system calls returning int, a 0 return value indicates success.
A -1 return value indicates an error, and an error code is stored in
errno.
HISTORY
The syscall() function call appeared in 4.0BSD.
BUGS
There is no way to simulate system calls that have multiple return values
such as pipe(2).
MirOS BSD #10-current June 16, 1993 1
