USP Lab Exam Today

Write a program to read a file and display it on the console
#define _POSIX_SOURCE
#define _POSIX_C_SOURCE 199309L
#include<stdio.h>
#include<unistd.h>
#include<fcntl.h>
#include<sys/types.h>
int main(int argc,char* argv[])
{
int fd1,n;
char buf1[2];
if(argc<2)
{
perror("Too few arguements...");
return 0;
}
fd1=open(argv[1],O_RDONLY);
 if(fd1==-1)
{
perror(" "); return 0;
}
while(n=read(fd1,buf1,1)>0)
write(1,buf1,1);
//printf("%c",buf1);
return 0;
}
Write a program to create and write Hello world to a file.
// C program to illustrate
// write system Call
#include<stdio.h>
#include <fcntl.h>
#include<string.h>
int main()
{
int sz;
int fd = open("foo.txt", O_WRONLY | O_CREAT | O_TRUNC, 0644);
if (fd < 0)
{
    perror("r1");
    return(0);
}
sz = write(fd, "hello world\n", strlen("hello world\n"));
close(fd);
return(0);
}
Write a program to find the type of the file given as an input
#define _POSIX_SOURCE
#define POSIX_C_SOURCE 199309L
#include<stdio.h>
#include<unistd.h>
#include<fcntl.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<string.h>
int main(int argc, char* argv[])
{
struct stat statv; char c[100];
if(stat(argv[1],&statv)==0)
printf("File exists\n");
 else
{
  printf("No file");
   return 0;
}
if(S_ISDIR(statv.st_mode))
 printf("Directory file\n");
if(S_ISCHR(statv.st_mode))
  printf("Character file\n");
if(S_ISBLK(statv.st_mode))
  printf("Block file\n");
if(S_ISLNK(statv.st_mode))
  printf("Symbolic link file\n");
if(S_ISFIFO(statv.st_mode))
  printf("FIFO or pipe\n");
if(S_ISREG(statv.st_mode))
  printf("Regular file\n");
return 0;
}
4. Write a C program that takes one or more file/directory names as command line
     input and reports the following information on the file:
File type
Number of links
Time of last access
Size of the file
Inode number
#define _POSIX_SOURCE
#define POSIX_C_SOURCE 199309L
#include<stdio.h>
#include<unistd.h>
#include<fcntl.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<string.h>
int main(int argc, char* argv[])
{
struct stat statv; char c[100];
if(stat(argv[1],&statv)==0)
printf("File exists\n");

else
{
printf("No file"); return 0;
}
if(S_ISDIR(statv.st_mode))
  printf("Directory file\n");
if(S_ISCHR(statv.st_mode))
   printf("Character file\n");
if(S_ISBLK(statv.st_mode))
   printf("Block file\n");
if(S_ISLNK(statv.st_mode))
  printf("Symbolic link file\n");
if(S_ISFIFO(statv.st_mode))
  printf("FIFO or pipe\n");
if(S_ISREG(statv.st_mode))
  printf("Regular file\n");
printf("Number of links: %d \n",statv.st_nlink);
printf("User id: %d\n",statv.st_uid);
 printf("Group id: %d\n",statv.st_gid);
printf("size of the file is %d\n",statv.st_size);
printf("Inode numberof the file is %d",statv.st_ino);
return 0;

}
5.Implement in C the following UNIX commands using system calls a) Cat b) mv
# include<stdio.h>
//# define PERROR -1
int main(int argc, char* argv[])
{
char op;
if((argc<3)||(argc>4))
{
fprintf(stderr,"ERROR");
return(0);
}
else
{
if(link(argv[1],argv[2])==-1)
{
perror(argv[0]);
}
if(unlink(argv[1])==-1)
{
perror(argv[1]);
}
}
printf("sucessfull");
return(0);
}
6.Implement in C the following UNIX commands using system calls a) cp b)ln
Cp
#define _POSIX_SOURCE
#define _POSIX_C_C_SOURCE 199309L
 #include<stdio.h>
#include<unistd.h>
#include<fcntl.h>
 #include<sys/types.h>
#include<string.h>
int main()
{
int fd1,n,fd2,n1;
char buf1[50],buf2[50],buf3[50],buf4[50];

fd2=open("file2.txt",O_WRONLY|O_CREAT|O_APPEND,777);
fd1=open("file1.txt",O_RDONLY);
if(fd1==-1 || fd2==-1)
{
perror(" ");
return 0;
}
while(n1=read(fd1,buf3,10)>0)
write(fd2,buf3,10);
close(fd2);
lseek(fd1,0,SEEK_SET);

close(fd1);
return 0;
}
LN
#define _POSIX_SOURCE
#define _POSIX_C_SOURCE 199309L
#include<stdio.h>
#include<unistd.h>
#include<fcntl.h>
#include<sys/types.h>
int main(int argc, char* argv[])
{
int fd,fd1;
if(argc<3)
{
perror("Too less arguements... ");
return 0;
}
fd=link(argv[1],argv[2]);
if(fd==0)
  printf("Linking successful\n");
else
  printf("Linking Unsuccessful\n");
//fd1=unlink(argv[1]); if(fd1==0)
//printf("Unlinking Successful\n");
//else
//printf("Unlinking unsuccessful\n");
return 0;
}
7.Write to read form key board and print it on the console using read write API
#define _POSIX_SOURCE
#define _POSIX_C_SOURCE 199309L
#include<stdio.h>
#include<unistd.h>
#include<fcntl.h>
#include<sys/types.h>
int main(int argc,char* argv[])
{
int fd1,n;
char buf1[2];
while(n=read(0,buf1,1)>0)
write(1,buf1,1);
//printf("%c",buf1);
return 0;
}
8.Write a program to create a file with 10 bytes of data from the beginning and 10 bytes of data from offset of 48 and display the contents of the file.
#define _POSIX_SOURCE
#define _POSIX_C_SOURCE 199309L
#include<stdio.h>
#include<unistd.h>
#include<fcntl.h>
#include<sys/types.h>
#include<sys/stat.h>
int main()
{
char c[2];
int fd1=open("file1.txt",O_WRONLY|O_CREAT|O_TRUNC,S_IRWXU|S_IROTH| S_IRGRP|S_IXGRP);
if(fd1==-1)
{
 perror(" ");
return 0;
}
else
{
printf(" File created..\n");
write(fd1,"We are quarantined since one month",35);
lseek(fd1,48,SEEK_CUR);
write(fd1," We are not sure when lockdown will be released",47);
close(fd1);
//fd1=open("file1.txt",O_RDONLY);
// while(read(fd1,c,1)>0)
//printf("%s",c);
//printf("\n");
return 0;
}
}
9.Write a C program to create a child process and allow the parent to display “parent” and the child to display “child” on the screen
#include<stdio.h>
#include<unistd.h>
int main()
{
int a=fork();
if(a<0)
printf("Child process creation unsuccessful...\n");
if(a==0)
printf("Child written by child process whose process id is: %d and its parent process has id: %d \n",getpid(),getppid());
if(a>0)
printf("Parent written by parent process with process id is: %d\n",getpid());
return 0;
}
10. Write a program to display the area of the circle in the child's process and the find
     the area of a square in the parent process.
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
int main()
{
int l,r;
float area,pi=3.142;
int a=vfork();
if(a<0)
printf("Child process creation unsuccessful \n");
if(a==0)
{
printf("Enter the radius of the circle: ");
 scanf("%d",&r);
area=pi * r * r;
printf("Area of the circle is: %f square units\n",area);
printf("It is created by the child process whose id is: %d and its prent has the process id: %d\n",getpid(),getppid());
//exit(0);
}
printf("Enter the length of side of a square:");
scanf("%d",&l);
area=l*l;
printf("Area of square is: %f square units\n",area);
printf("It is calculated by the parent process whose process id is: %d\n",getpid()); return 0;
}

Write a program that creates the child using fork system call and one process finds the sum of odd series and the other process finds the sum of even series.

#include <iostream>
#include <unistd.h>
using namespace std;
int main()
{
    int a[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
    int sumOdd = 0, sumEven = 0, n, i;
    n = fork();
    if (n > 0) {
        for (i = 0; i < 10; i++) {
            if (a[i] % 2 == 0)
                sumEven = sumEven + a[i];
        }
        cout<<"Parent process\n";
        cout<<"Sum of even no. is "<<sumEven<<endl;
    }

    // If n is 0 i.e. we are in child process
    else {
        for (i = 0; i < 10; i++) {
            if (a[i] % 2 != 0)
                sumOdd = sumOdd + a[i];
        }
        cout<< "Child process \n";
        cout<< "\nSum of odd no. is " <<sumOdd<<endl;
    }
    return 0;
}