|_SYSCALL(2)||Linux Programmer's Manual||_SYSCALL(2)|
NAME_syscall - invoking a system call without library support (OBSOLETE)
DESCRIPTIONThe important thing to know about a system call is its prototype. You need to know how many arguments, their types, and the function return type. There are seven macros that make the actual call into the system easier. They have the form:
- X is 0–6, which are the number of arguments taken by the system call
- type is the return type of the system call
- name is the name of the system call
- typeN is the Nth argument's type
- argN is the name of the Nth argument
These macros create a function called name with the arguments you specify. Once you include the _syscall() in your source file, you call the system call by name.
CONFORMING TOThe use of these macros is Linux-specific, and deprecated.
NOTESStarting around kernel 2.6.18, the _syscall macros were removed from header files supplied to user space. Use syscall(2) instead. (Some architectures, notably ia64, never provided the _syscall macros; on those architectures, syscall(2) was always required.)
#include <linux/unistd.h> /* for _syscallX macros/related stuff */
#include <linux/kernel.h> /* for struct sysinfo */
_syscall1(int, sysinfo, struct sysinfo *, info);
/* Note: if you copy directly from the nroff source, remember to
REMOVE the extra backslashes in the printf statement. */
struct sysinfo s_info;
error = sysinfo(&s_info);
printf("code error = %d\n", error);
printf("Uptime = %lds\nLoad: 1 min %lu / 5 min %lu / 15 min %lu\n"
"RAM: total %lu / free %lu / shared %lu\n"
"Memory in buffers = %lu\nSwap: total %lu / free %lu\n"
"Number of processes = %d\n",
code error = 0
uptime = 502034s
Load: 1 min 13376 / 5 min 5504 / 15 min 1152
RAM: total 15343616 / free 827392 / shared 8237056
Memory in buffers = 5066752
Swap: total 27881472 / free 24698880
Number of processes = 40
SEE ALSOintro(2), syscall(2), errno(3)
COLOPHONThis page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.