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31.\"     @(#)syscall.2	8.1 (Berkeley) 6/16/93
32.\"
33.Dd June 16, 1993
34.Dt SYSCALL 2
35.Os
36.Sh NAME
37.Nm syscall ,
38.Nm __syscall
39.Nd indirect system call
40.Sh SYNOPSIS
41.Fd #include <sys/syscall.h>
42.Fd #include <unistd.h>
43.Ft int
44.Fn syscall "int number" "..."
45.Fn __syscall "quad_t number" "..."
46.Sh DESCRIPTION
47.Fn syscall
48performs the system call whose assembly language
49interface has the specified
50.Fa number
51with the specified arguments.
52Symbolic constants for system calls can be found in the header file
53.Ao Pa sys/syscall.h Ac .
54.Pp
55Since different system calls have different return types, a
56prototype of
57.Nm __syscall
58specifying the correct return type should be declared locally.
59This is especially important for system calls returning
60larger-than-int results.
61.Pp
62The
63.Nm __syscall
64form should be used when one or more of the parameters is a
6564-bit argument to ensure that argument alignment is correct.
66This system call is useful for testing new system calls that
67do not have entries in the C library.
68.Sh RETURN VALUES
69The return values are defined by the system call being invoked.
70In general, for system calls returning
71.Va int ,
72a 0 return value indicates success.
73A \-1 return value indicates an error,
74and an error code is stored in
75.Va errno .
76.Sh HISTORY
77The
78.Fn syscall
79function call appeared in
80.Bx 4.0 .
81.Sh BUGS
82There is no way to simulate system calls that have multiple return values
83such as
84.Xr pipe 2 .
85