1 .\" Copyright (c) 1993 Michael Haardt (michael@moria.de),
2 .\" Fri Apr 2 11:32:09 MET DST 1993
4 .\" %%%LICENSE_START(GPLv2+_DOC_FULL)
5 .\" This is free documentation; you can redistribute it and/or
6 .\" modify it under the terms of the GNU General Public License as
7 .\" published by the Free Software Foundation; either version 2 of
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10 .\" The GNU General Public License's references to "object code"
11 .\" and "executables" are to be interpreted as the output of any
12 .\" document formatting or typesetting system, including
13 .\" intermediate and printed output.
15 .\" This manual is distributed in the hope that it will be useful,
16 .\" but WITHOUT ANY WARRANTY; without even the implied warranty of
17 .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 .\" GNU General Public License for more details.
20 .\" You should have received a copy of the GNU General Public
21 .\" License along with this manual; if not, see
22 .\" <http://www.gnu.org/licenses/>.
25 .\" Tue Jul 6 12:42:46 MDT 1993 <dminer@nyx.cs.du.edu>
26 .\" Added "Calling Directly" and supporting paragraphs
28 .\" Modified Sat Jul 24 15:19:12 1993 by Rik Faith <faith@cs.unc.edu>
30 .\" Modified 21 Aug 1994 by Michael Chastain <mec@shell.portal.com>:
31 .\" Added explanation of arg stacking when 6 or more args.
33 .\" Modified 10 June 1995 by Andries Brouwer <aeb@cwi.nl>
35 .\" 2007-10-23 mtk: created as a new page, by taking the content
36 .\" specific to the _syscall() macros from intro(2).
38 .TH _SYSCALL 2 2007-12-19 "Linux" "Linux Programmer's Manual"
40 _syscall \- invoking a system call without library support (OBSOLETE)
42 .B #include <linux/unistd.h>
48 The important thing to know about a system call is its prototype.
49 You need to know how many arguments, their types,
50 and the function return type.
51 There are seven macros that make the actual call into the system easier.
55 .RI _syscall X ( type , name , type1 , arg1 , type2 , arg2 ,...)
61 is 0\(en6, which are the number of arguments taken by the
65 is the return type of the system call
68 is the name of the system call
71 is the Nth argument's type
74 is the name of the Nth argument
76 These macros create a function called
78 with the arguments you
80 Once you include the _syscall() in your source file,
81 you call the system call by
84 .I /usr/include/linux/unistd.h
86 The use of these macros is Linux-specific, and deprecated.
88 Starting around kernel 2.6.18, the _syscall macros were removed
89 from header files supplied to user space.
93 (Some architectures, notably ia64, never provided the _syscall macros;
94 on those architectures,
102 create one, especially for C++ users.
104 System calls are not required to return only positive or negative error
106 You need to read the source to be sure how it will return errors.
107 Usually, it is the negative of a standard error code,
110 The _syscall() macros will return the result
115 is nonnegative, but will return \-1 and set the variable
122 For the error codes, see
125 When defining a system call, the argument types
128 passed by-value or by-pointer (for aggregates like structs).
129 .\" The preferred way to invoke system calls that glibc does not know
132 .\" However, this mechanism can be used only if using a libc
133 .\" (such as glibc) that supports
136 .\" .I <sys/syscall.h>
137 .\" header file contains the required SYS_foo definition.
138 .\" Otherwise, the use of a _syscall macro is required.
145 #include <linux/unistd.h> /* for _syscallX macros/related stuff */
146 #include <linux/kernel.h> /* for struct sysinfo */
148 _syscall1(int, sysinfo, struct sysinfo *, info);
150 /* Note: if you copy directly from the nroff source, remember to
151 REMOVE the extra backslashes in the printf statement. */
156 struct sysinfo s_info;
159 error = sysinfo(&s_info);
160 printf("code error = %d\\n", error);
161 printf("Uptime = %lds\\nLoad: 1 min %lu / 5 min %lu / 15 min %lu\\n"
162 "RAM: total %lu / free %lu / shared %lu\\n"
163 "Memory in buffers = %lu\\nSwap: total %lu / free %lu\\n"
164 "Number of processes = %d\\n",
165 s_info.uptime, s_info.loads[0],
166 s_info.loads[1], s_info.loads[2],
167 s_info.totalram, s_info.freeram,
168 s_info.sharedram, s_info.bufferram,
169 s_info.totalswap, s_info.freeswap,
178 Load: 1 min 13376 / 5 min 5504 / 15 min 1152
179 RAM: total 15343616 / free 827392 / shared 8237056
180 Memory in buffers = 5066752
181 Swap: total 27881472 / free 24698880
182 Number of processes = 40
189 This page is part of release 3.68 of the Linux
192 A description of the project,
193 information about reporting bugs,
194 and the latest version of this page,
196 \%http://www.kernel.org/doc/man\-pages/.