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SYSCALL(2) FreeBSD System Calls Manual SYSCALL(2)
NAME
syscall, __syscall - indirect system call
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/syscall.h>
#include <unistd.h>
int
syscall(int number, ...);
off_t
__syscall(quad_t number, ...);
DESCRIPTION
The syscall() function 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 arguments 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
general, 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 appeared in 4.0BSD.
BUGS
There is no way to simulate system calls that have multiple return values
such as pipe(2).
FreeBSD 14.0-RELEASE-p6 June 16, 1993 FreeBSD 14.0-RELEASE-p6