Updated: Mar 23, 2020

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Process in Linux

Code:AL000015

By: Sameer Sengupta

Article contents

• What is a process in linux?
• Creating a Linux process
• States of process, Zombie process
• Creating a process using fork
• Getting process ID(PID) and group

Learn linux process, creating a process, states of linux process, zombie process, creating process using fork system call, getting process ID(PID) and group info using system calls.

What is a linux process?

A process is an active program i.e. a program that is under execution.

Creating a Linux process

Let's write the following small program square.c and create an executable SQUARE for it.

#include "stdio.h"
void main()
{
        int num;
        start:
        printf("Enter a number\n");
        scanf("%d",&num);
        while(num < 10)
        {
                printf("Square of your number:%d\n",num * num);
                goto start;
        }
}

$ gcc square.c -o SQUARE
$ ./SQUARE
Enter a number
3
Square of your number:9
Enter a number
5
Square of your number:25
Enter a number

Let's open another console and execute ps -aux command to observe the process we have created.

$ ps -aux
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root         1  0.0  0.6  26936  5940 ?        Ss   01:46   0:02 /sbin/init splash
pi        2063  0.0  0.0   1812   328 pts/0    S+   05:09   0:00 ./SQUARE
pi        2115  0.0  0.3   7736  2868 pts/1    R+   05:13   0:00 ps -aux
$ 

When we executed the ps -aux command we got all processes information detail. I have intentionally removed the other processes and kept few lines for your observation

States of process, Zombie process