EmbLogic » Sweety Hooda

Sweety Hooda — Sat, 21 Jun 2014 06:49:57 +0000

head 1.1; access; symbols; locks emblogic:1.1; strict; comment @ * @; 1.1 date 2014.06.21.06.46.49; author emblogic; state Exp; branches; next ; desc @create a module.. using module_init and module_exit system calls.. then insert and delete the module from the list … Continue reading →

introduction to semaphore and initialization of semaphore..

Sweety Hooda — Tue, 13 May 2014 11:10:55 +0000

Semaphores are a programming construct designed by E. W. Dijkstra in the late 1960s. Dijkstra’s model was the operation of railroads: consider a stretch of railroad in which there is a single track over which only one train at a time is allowed. Guarding this track is a semaphore. A train must wait before entering the single track until the semaphore is in a state that permits travel. When the train enters the track, the semaphore changes state to prevent other trains from entering the track. A train that is leaving this section of track must again change the state of the semaphore to allow another train to enter. In the computer version, a semaphore appears to be a simple integer. A process (or a thread) waits for permission to proceed by waiting for the integer to become 0. The signal if it proceeds signals that this by performing incrementing the integer by 1. When it is finished, the process changes the semaphore’s value by subtracting one from it.

Initializing a Semaphore Set

The function semget() initializes or gains access to a semaphore. It is prototyped by:

int semget(key_t key, int nsems, int semflg);

When the call succeeds, it returns the semaphore ID (semid).

The key argument is a access value associated with the semaphore ID.

The nsems argument specifies the number of elements in a semaphore array. The call fails when nsems is greater than the number of elements in an existing array; when the correct count is not known, supplying 0 for this argument ensures that it will succeed.

The semflg argument specifies the initial access permissions and creation control flags.

file i/o(changing the existing password in a file )

Sweety Hooda — Mon, 12 May 2014 08:30:36 +0000

#include
#include
#include
int main()
{
char *pwd=NULL;
char *pwd1=NULL;
int ch=0,i=0,ret,len;
char *buff;
pwd=malloc(sizeof(char) *10);
pwd1=malloc(sizeof(char) *10);
buff=malloc(sizeof(char) *10);
FILE *fptr = NULL;
fptr=fopen(“hello.txt”,”r+”);
if(fptr == NULL)
{
perror(“fopen”);
return -1;
}
else
printf(“file is opened successfully\n”);
printf(“enter old password\n”);
gets(pwd);
ch=getc(fptr);
while(ch!=EOF)
{
if(ch!=’\n’)
{
buff[i]=ch;
ch=getc(fptr);
i++;
}
else
{
ret=strcmp(buff,pwd);
if(ret==0)
{
printf(“\nenter new password::”);
gets(pwd);
printf(“\nconfirm password::”);
gets(pwd1);
ret=strcmp(pwd,pwd1);
while(ret!=0)
{
for(i=0;i<3;i++)
{
printf(“both passwords are not same\n”);
printf(“enter the confirm password again::”);
gets(pwd1);
ret=strcmp(pwd,pwd1);
}
printf(“u have tried maximum times..\n Try again after some time\n”);
break;
}
if(ret==0)
{
len=strlen(pwd1);
ret=fseek(fptr,-(len+1),SEEK_CUR);
ret=fputs(pwd1,fptr);
ret=fputc(‘\n’,fptr);
printf(“\npassword changed..\n”);
}
}
else
{
i=0;
ch=fgetc(fptr);
}
}
}
return 0;
}

file i/o(open a file which contains passwords and login by matching the password entered by user.)

Sweety Hooda — Sun, 11 May 2014 11:35:49 +0000

#include
#include
#include
int main()
{
char *pwd=NULL;
int ch=0,i=0,ret;
char *buff;
pwd=malloc(sizeof(char) *10);
buff=malloc(sizeof(char) *10);
FILE *fptr = NULL;
fptr=fopen(“hello.txt”,”r+”);
if(fptr == NULL)
{
perror(“fopen”);
return -1;
}
else
printf(“file is opened successfully\n”);
printf(“enter the password\n”);
gets(pwd);
ch=getc(fptr);
while(ch!=EOF)
{
if(ch!=’\n’)
{
buff[i]=ch;
ch=getc(fptr);
i++;
}
else
{
ret=strcmp(buff,pwd);
if(ret==0)
{
printf(“login successfully..\n”);
exit(0);
}
else
{
i=0;
ch=fgetc(fptr);
}
}
}
if(ch==EOF)
{
printf(“wrong password..try again\n”);
}
return 0;
}

how to copy a string in a array..

Sweety Hooda — Tue, 25 Mar 2014 09:52:56 +0000

if we want to insert the elements of a string into a array like

char a[20]=”hello”;

then it will show a error…

because a (array name) is a constant pointer..whose address can not be changed…

and here we try to assign a new address of ‘h’ to the array name..

so we have to use strcpy(built in func) to insert the elements of string in a array….

linklist

Sweety Hooda — Tue, 25 Mar 2014 09:43:47 +0000

The following code inserts a node after an existing node in a singly linked list. The diagram shows how it works. Inserting a node before an existing one cannot be done directly; instead, one must keep track of the previous node and insert a node after it.

 function insertAfter(Node node, Node newNode) // insert newNode after node
     newNode.next := node.next
     node.next    := newNode

Inserting at the beginning of the list requires a separate function. This requires updating firstNode.