Program to copy the content of one file into another file in C

#include<stdio.h>

void main()
{
 FILE *f1,*f2,*f3;
 char fn[10],a[1000],buff[1000];
 int i,j;
     
  printf("Enter the file name::");
  gets(fn);
 
     f1 = fopen(fn,"w");
   printf("Enter the content of the File::");
     gets(a);
     fprintf(f1,"%s",a);
 fclose(f1);

    f2 = fopen(fn,"r");
    f3 = fopen("fat.txt","w");
     while( fgets(buff,1000,f2) != NULL )
        fprintf(f3,"%s",buff);
 fclose(f2);
 fclose(f3);
  printf("The content of the File::");
    f3 = fopen("fat.txt","r");
   while( fgets(a,1000,f3) != NULL )
     {
       printf("%s",a);  
     }
 printf("\n");
 fclose(f3);
}

Function getche() for linux user

#include <stdio.h>
#include <termios.h>
#include <unistd.h>


int getche(void)
{
    struct termios oldattr, newattr;
    int ch;
    tcgetattr( STDIN_FILENO, &oldattr );
    newattr = oldattr;
    newattr.c_lflag &= ~( ICANON );
    tcsetattr( STDIN_FILENO, TCSANOW, &newattr );
    ch = getchar();
    tcsetattr( STDIN_FILENO, TCSANOW, &oldattr );
    return ch;
}

Program to implement security access in c - U can include this function and can provide two level of security

#include <stdio.h>
#include <termios.h>
#include <unistd.h>

int getch(void)
{
    struct termios oldattr, newattr;
    int ch;
    tcgetattr( STDIN_FILENO, &oldattr );
    newattr = oldattr;
    newattr.c_lflag &= ~( ICANON | ECHO );
    tcsetattr( STDIN_FILENO, TCSANOW, &newattr );
    ch = getchar();
    tcsetattr( STDIN_FILENO, TCSANOW, &oldattr );
    return ch;
}

int getche(void)
{
    struct termios oldattr, newattr;
    int ch;
    tcgetattr( STDIN_FILENO, &oldattr );
    newattr = oldattr;
    newattr.c_lflag &= ~( ICANON );
    tcsetattr( STDIN_FILENO, TCSANOW, &newattr );
    ch = getchar();
    tcsetattr( STDIN_FILENO, TCSANOW, &oldattr );
    return ch;
}


void main()
{
char pasword[10],usrname[10], ch;
int i;

//clrscr();

printf("Enter User name: ");
gets(usrname);
printf("Enter the password <any 8 characters>: ");

for(i=0;i<8;i++)
{
ch = getch();
pasword[i] = ch;
ch = '*' ;
printf("%c",ch);
}

pasword[i] = '\0';

/*If you want to know what you have entered as password, you can print it*/
printf("\nYour password is :");

for(i=0;i<8;i++)
{
printf("%c",pasword[i]);
}
printf("\n");
}

Function for getch() for linux --- Since we can't use getch in linux including this function u can also use it on linux..

#include <stdio.h>
#include <termios.h>
#include <unistd.h>

int getch(void)
{
    struct termios oldattr, newattr;
    int ch;
    tcgetattr( STDIN_FILENO, &oldattr );
    newattr = oldattr;
    newattr.c_lflag &= ~( ICANON | ECHO );
    tcsetattr( STDIN_FILENO, TCSANOW, &newattr );
    ch = getchar();
    tcsetattr( STDIN_FILENO, TCSANOW, &oldattr );
    return ch;
}

Singly List made Simple for who find it difficult programmed in C

#include <stdio.h> 
#include <stdlib.h> 
 
//Structure containing a Data part & a 
//Link part to the next node in the List 
 
struct Node 
{ 
 int Data; 
 struct Node *Next; 
}*Head; 
 
// Counting number of elements in the List 
 
int length() 
{ 
  struct Node *cur_ptr; 
  int count=0; 
 
  cur_ptr=Head; 
 
  while(cur_ptr != NULL) 
  { 
     cur_ptr=cur_ptr->Next; 
     count++; 
  } 
  return(count); 
} 
 
// Deleting a node from List depending upon the data in the node. 
 
int delNodeData(int num) 
{ 
  struct Node *prev_ptr, *cur_ptr; 
 
  cur_ptr=Head; 
 
  while(cur_ptr != NULL) 
  { 
     if(cur_ptr->Data == num) 
     { 
        if(cur_ptr==Head) 
        { 
           Head=cur_ptr->Next; 
           free(cur_ptr); 
           return 0; 
        } 
        else 
        { 
           prev_ptr->Next=cur_ptr->Next; 
           free(cur_ptr); 
           return 0; 
        } 
     } 
     else 
     { 
        prev_ptr=cur_ptr; 
        cur_ptr=cur_ptr->Next; 
     } 
  } 
 
  printf("\nElement %d is not found in the List", num); 
  return 1; 
} 
 
// Deleting a node from List depending upon the location in the list. 
 
int delNodeLoc(int loc) 
{ 
  struct Node *prev_ptr, *cur_ptr; 
  int i; 
 
  cur_ptr=Head; 
 
  if(loc > (length()) || loc <= 0) 
  { 
      printf("\nDeletion of Node at given location is not possible\n "); 
  } 
  else 
  { 
      // If the location is starting of the list 
      if (loc == 1) 
      { 
          Head=cur_ptr->Next; 
          free(cur_ptr); 
          return 0; 
      } 
      else 
      { 
          for(i=1;i<loc;i++) 
          { 
              prev_ptr=cur_ptr; 
              cur_ptr=cur_ptr->Next; 
          } 
 
          prev_ptr->Next=cur_ptr->Next; 
          free(cur_ptr); 
      } 
  } 
  return 1; 
} 
 
//Adding a Node at the end of the list 
 
void addEnd(int num) 
{ 
  struct Node *temp1, *temp2; 
 
  temp1=(struct Node *)malloc(sizeof(struct Node)); 
  temp1->Data=num; 
 
  // Copying the Head location into another node. 
  temp2=Head; 
 
  if(Head == NULL) 
  { 
     // If List is empty we create First Node. 
     Head=temp1; 
     Head->Next=NULL; 
  } 
  else 
  { 
     // Traverse down to end of the list. 
     while(temp2->Next != NULL) 
     temp2=temp2->Next; 
 
     // Append at the end of the list. 
     temp1->Next=NULL; 
     temp2->Next=temp1; 
  } 
} 
 
// Adding a Node at the Beginning of the List 
 
void addBeg(int num) 
{ 
  struct Node *temp; 
 
  temp=(struct Node *)malloc(sizeof(struct Node)); 
  temp->Data = num; 
 
  if (Head == NULL) 
  { 
     //List is Empty 
     Head=temp; 
     Head->Next=NULL; 
  } 
  else 
  { 
     temp->Next=Head; 
     Head=temp; 
  } 
} 
 
// Adding a new Node at specified position 
 
void addAt(int num, int loc) 
{ 
  int i; 
  struct Node *temp, *prev_ptr, *cur_ptr; 
 
  cur_ptr=Head; 
 
  if(loc > (length()+1) || loc <= 0) 
  { 
     printf("\nInsertion at given location is not possible\n "); 
  } 
  else 
  { 
      // If the location is starting of the list 
      if (loc == 1) 
      { 
          addBeg(num); 
      } 
      else 
      { 
          for(i=1;i<loc;i++) 
          { 
              prev_ptr=cur_ptr; 
              cur_ptr=cur_ptr->Next; 
          } 
 
          temp=(struct Node *)malloc(sizeof(struct Node)); 
          temp->Data=num; 
 
          prev_ptr->Next=temp; 
          temp->Next=cur_ptr; 
      } 
  } 
} 
 
// Displaying list contents 
 
void display() 
{ 
  struct Node *cur_ptr; 
 
  cur_ptr=Head; 
 
  if(cur_ptr==NULL) 
  { 
     printf("\nList is Empty"); 
  } 
  else 
  { 
      printf("\nElements in the List: "); 
      //traverse the entire linked list 
      while(cur_ptr!=NULL) 
      { 
          printf(" -> %d ",cur_ptr->Data); 
          cur_ptr=cur_ptr->Next; 
      } 
      printf("\n"); 
  } 
} 
 
//Reversesing a Linked List 
 
void reverse() 
{ 
  struct Node *prev_ptr, *cur_ptr, *temp; 
 
  cur_ptr=Head; 
  prev_ptr=NULL; 
 
  while(cur_ptr != NULL) 
  { 
     temp=prev_ptr; 
     prev_ptr=cur_ptr; 
 
     cur_ptr=cur_ptr->Next; 
     prev_ptr->Next=temp; 
  } 
 
  Head=prev_ptr; 
} 
 
 
int main() 
{ 
 int i=0; 
 
 //Set HEAD as NULL 
 Head=NULL; 
 
 while(1) 
 { 
    printf("\n####################################################\n"); 
    printf("MAIN MENU\n"); 
    printf("####################################################\n"); 
    printf(" \nInsert a number \n1. At the Beginning"); 
    printf(" \n2. At the End"); 
    printf(" \n3. At a Particular Location in the List"); 
    printf(" \n\n4. Print the Elements in the List"); 
    printf(" \n5. Print number of elements in the List"); 
    printf(" \n6. Reverse the linked List"); 
    printf(" \n\nDelete a Node in the List"); 
    printf(" \n7. Delete a node based on Value"); 
    printf(" \n8. Delete a node based on Location\n"); 
    printf(" \n\n9. Exit\n"); 
    printf(" \nChoose Option: "); 
    scanf("%d",&i); 
 
    switch(i) 
    { 
      case 1: 
      { 
          int num; 
          printf(" \nEnter a Number to insert in the List: "); 
          scanf("%d",&num); 
          addBeg(num); 
          display(); 
          break; 
      } 
 
      case 2: 
      { 
          int num; 
          printf(" \nEnter the Number to insert: "); 
          scanf("%d",&num); 
          addEnd(num); 
          display(); 
          break; 
      } 
 
      case 3: 
      { 
          int num, loc; 
          printf("\nEnter the Number to insert: "); 
          scanf("%d",&num); 
          printf("\nEnter the location Number in List at which the Number is inserted: ");        
          scanf("%d",&loc); 
          addAt(num,loc); 
          display(); 
          break; 
      } 
 
      case 4: 
      { 
          display(); 
          break; 
      } 
 
      case 5: 
      { 
          display(); 
          printf(" \nTotal number of nodes in the List: %d",length()); 
          break; 
      } 
 
      case 6: 
      { 
          reverse(); 
          display(); 
          break; 
      } 
 
      case 7: 
      { 
          int num; 
          printf(" \nEnter the number to be deleted from List: "); 
          scanf("%d",&num); 
          delNodeData(num); 
          display(); 
          break; 
      } 
 
      case 8: 
      { 
          int num; 
          printf(" \nEnter the location of the node to  be deleted from List: ");    
          scanf("%d",&num); 
          delNodeLoc(num); 
          display(); 
          break; 
      } 
 
      case 9: 
      { 
          struct Node *temp; 
 
          while(Head!=NULL) 
          { 
              temp = Head->Next; 
              free(Head); 
              Head=temp; 
          } 
          exit(0); 
      } 
 
      default: 
      { 
          printf("\nWrong Option choosen"); 
      } 
    }/* end if switch */ 
 }/* end of while */ 
}/* end of main */