Thread: How to check if a process is runing using PID

Hello!
I need to find 3 ways and explain the advantages and disadvantages of them..
The first that I used is kill like that:

Code:

#include"stdio.h"


#include<signal.h>


#include<unistd.h>

#include<errno.h>

#include<stdlib.h>

int main(int argc, char **argv ){

long a = strtol(argv[1], NULL, 10);

kill( a, 0);

int b= errno;


if(errno == 3){


printf("Process %s does not exist \n",argv[1]);


}


else if(errno == 1){


printf("Process %s exists but we have no permission \n",argv[1]);


}


else{


printf("Process %s exists \n",argv[1]);


}


}

I did this with kill but I have no idea how to find 2 more and explain the advantages and disadvantages

Please help!!

Thanks man, this is a good way the problem is what are the advantages and disadvantages ? This is the hard part that I can't explain

I have no clue on how to use it
Everywhere I look it say that I can use -1 0 1 in the pid and I wish to put my own also there is a stract involved that I have no idea how to use
Could you help with a sample code?