Hello,
Here is an example from chapter 5 of the book "Explore BeagleBone" by Derek
Molloy:
#include<gnu/libc-version.h>
#include<sys/syscall.h>
#include<sys/types.h>
#include<iostream>
#include<signal.h>
using namespace std;
int main(){
//gnu_get_libc_version() returns a string that identifies the
//glibc version available on the system.
cout << "The GNU libc version is " << gnu_get_libc_version() << endl;
// process id tid is thread identifier
// look inside sys/syscall.h for System Call Numbers
pid_t tid; //pid_t is of type integer
tid = syscall(SYS_gettid); // make a system call to get the process id
cout << "The Current PID is: " << tid << endl;
//can also get by calling getpid() function from signal.h
cout << "The Current PID is: " << getpid() << endl;
// Can get current UserID by using:
int uid = syscall(SYS_getuid);
cout << "It is being run by user with ID: " << uid << endl;
// or getting the value from syscalls.kernelgrok.com
uid = syscall(0xc7);
cout << "It is being run by user with ID: " << uid << endl;
return 0;
}
It isn't compiled:
debian@beaglebone:~/exploringbb/chp05/syscall$ g++ syscall.cpp -o syscall
syscall.cpp: In function ‘int main()’:
syscall.cpp:22:10: error: ‘syscall’ was not declared in this scope
tid = syscall(SYS_gettid); // make a system call to get the process id
^~~~~~~
syscall.cpp:22:10: note: suggested alternative: ‘swscanf’
tid = syscall(SYS_gettid); // make a system call to get the process id
^~~~~~~
swscanf
syscall.cpp:25:38: error: ‘getpid’ was not declared in this scope
cout << "The Current PID is: " << getpid() << endl;
^~~~~~
syscall.cpp:25:38: note: suggested alternative: ‘getpt’
cout << "The Current PID is: " << getpid() << endl;
^~~~~~
getpt
debian@beaglebone:~/exploringbb/chp05/syscall$
Indeed, I searched for syscall declaration in the toolchain ... and didn't
find it:
debian@beaglebone:~/exploringbb/chp05/syscall$ sudo grep -rn
/usr/include/arm-linux-gnueabihf/ -e "syscall("
[sudo] password for debian:
debian@beaglebone:~/exploringbb/chp05/syscall$
Any comments ?
Thanks.
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