NAME    [Toc]    [Back]

     syscall, __syscall - indirect system call

LIBRARY    [Toc]    [Back]

     Standard C Library (libc, -lc)

SYNOPSIS    [Toc]    [Back]

     #include <sys/syscall.h>
     #include <unistd.h>

     int
     syscall(int number, ...);

     quad_t
     __syscall(quad_t number, ...);

DESCRIPTION    [Toc]    [Back]

     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 system
 call is useful for testing new system calls that do not have entries
     in the C library.

RETURN VALUES    [Toc]    [Back]

     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    [Toc]    [Back]

     The syscall() function call appeared in 4.0BSD.

BUGS    [Toc]    [Back]

     There is no way to simulate system calls that have multiple return values
     such as pipe(2).

     Due to ABI implementation differences in passing struct or union type
     arguments to system calls between different processors, all system calls
     pass instead pointers to such structs or unions, even when the documentation
 of the system call mentions otherwise. The conversion between passing
 structs and unions is handled normally via userland stubs. The correct
 arguments for the kernel entry points for each system call can be
     found in the header file <sys/syscallargs.h>

BSD                              June 16, 1993                             BSD