Exploring Basic Linux System Calls

Problem Statement

Explore the usage of basic Linux system calls.

Process Management System Calls

The system calls to manage processes are:

• fork(): Used to create a new process.
• exec(): Executes a new program.
• wait(): Waits until the process finishes execution.
• exit(): Exits from the process.

System calls used to get process IDs are:

• getpid(): Gets the unique process ID of the process.
• getppid(): Gets the parent process's unique ID.

Stat System Call

The stat system call retrieves information about files, specifically from their inodes. For instance, to get a file's size and name, you would typically use stat. Let's illustrate with a C code snippet (src/ls1.c):

#include<stdio.h>
#include<dirent.h>
#include<cstdlib>

struct dirent *dptr;

int main(int argc, char *argv[])
{
    char buff[100];
    DIR*dirp;

    printf("\n\nANUBHAV-VERMA_SE-15_50\n\n");
    printf("ENTER DIRECTORY NAME \n\n");
    scanf("%s", buff);

    if((dirp=opendir(buff))==NULL)
    {
        printf("The given directory does not exist");
        exit(1);
    }

    while(dptr=readdir(dirp))
    {
        printf("%s\n",dptr->d_name);
    }

    closedir(dirp);
}

In this code:

• opendir() opens the directory.
• readdir() reads each directory entry.
• closedir() closes the directory.

Deleting Directories

Two commands delete directories in Linux:

• rmdir: Deletes an empty directory.

  $ rmdir <directory name>
  

• rm -rf: Deletes a directory and its contents recursively.

  $ rm -rf <directory name>
  

  Caution: Use rm -rf with extreme care, as it permanently deletes data.