These are a list of various unix system calls that are implemented in C. If you have any doubts, please let me know.

PROGRAM DEVELOPMENT

#include<stdio.h>

#include<dirent.h>

struct dirent *dptr;

void main(int argc, char *argv[])

{

  char buff[100];

  DIR *dirp;

  printf("\n\nEnter Directory Name: ");

  scanf("%s",buff);

  if((dirp=opendir(buff))==NULL)

  {

   printf("\n The given directory does not exist\n");

   exit(1);

  }

  while(dptr=readdir(dirp))

  {

    printf("%s\n",dptr->d_name);

  }

  closedir(dirp);

}

PROGRAM DEVELOPMENT

#include<stdio.h>

#include<unistd.h>

main()

{

  int pid,pid1,pid2;

  pid=fork();

  if(pid==-1)

  {

    printf("ERROR IN PROCESS CREATION\n");

    exit(1);

  }

  if(pid!=0)

  {

   pid1=getpid();

   printf("\nThe parent process id is %d\n",pid1);

   }

  else

   {

    pid2=getpid();

   printf("\nThe child process id is %d\n",pid2);

  }

}

PROGRAM DEVELOPMENT

#include<stdio.h>

int main()

{

  int fd;

  if((fd=open("file.dat"))==-1)

  {

   perror("cannot open the file.dat");

   exit(0);

  }

  else

  printf("\nFILE OPENED SUCCESSFULLY");

  return 0;

}

PROGRAM DEVELOPMENT

#include<stdio.h>

main()

{

 char b[20];

 int fd,xr;

 if((fd=open("balaji",0))==-1)

 {

  printf("Cannot open file\n");

  exit(1);

 }

 do

 {

   xr=read(fd,b,20);

   b[xr]='\0';

   printf("%s",b);

 }

while(xr==20);

 close(fd);

}

PROGRAM DEVELOPMENT

#include<stdio.h>

main(int ac,char *av[])

 {

  int fd;

  int i=1,j=0;

  char *sep="";

  printf("%s",av[1]);

  if(ac<1)

  {

   printf("\n INSUFFICIENT ARGUMENTS");

   exit(1);

  }

  if((fd=open("balaji",0660))==-1)

  {

   printf("\n cannot create the file");

   exit(1);

  }

  while(i<ac)

  {

 j=write(fd,av[i],(unsigned)strlen(av[i]));

  printf("%d",j);

   write(fd,sep,(unsigned)strlen(sep));

   i++;

   }

   close(fd);

}

PROGRAM DEVELOPMENT

#include<stdio.h>

#include<unistd.h>

#include<sys/types.h>

#include<sys/stat.h>

int main()

{

 int s;

 struct stat st;

  s=stat("sss.c",&st);

  if(s<0)

  {

   printf("use of stat() is unsuccessful\n");

  exit(0); 

   }

   printf("\ninode number of sss.c file is %d",st.st_ino);

   printf("\nnumber of links to sss.c is %d",st.st_nlink);

   printf("\nfile permissions of sss.c file is %d",st.st_mode);

   printf("\nsize of sss.c file is %d",st.st_size);

   printf("\nlast access time of sss.c file is %d\n",st.st_atime);

}

Creating, writing to and reading from shared memory program

This is an operating systems program to implement creating, writing to and reading from a shared memory. If you have any doubts please let me know.

#include<sys/mman.h>                                                                                                                                                                                                                           

#include<sys/stat.h>

#include<fcntl.h>

#include<stdio.h>

main()

{

    int fd;

    char mamname[20];

    printf(“\nEnter the shared memory name: “);

   scanf(“%s”,memname);

   fd=shm_open(memname,O_CREAT,S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH);

   ftruncate(fd,100);

   if(fd>0)

   printf(“\nSUCCESS”);

   else

   printf(“\nFAIL”);

}

#include<sys/mman.h>                                                                                                                                                                                                                            

#include<sys/stat.h>

#include<fcntl.h>

#include<stdio.h>

main()

{

    int fd,i;

    char mamname[20];

    unsigned char *ptr;

    printf(“\nEnter the shared memory name: “);

   scanf(“%s”,memname);

   fd=shm_open(memname,O_CREAT,S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH);

   ptr=mmap(NULL,100,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);

   for(i=0;*(ptr+i)!=’\0’;i++)

    printf(“%c”,*(ptr+i));

}

#include<sys/mman.h>                                                                                                                                                                                                                            

#include<sys/stat.h>

#include<fcntl.h>

#include<stdio.h>

main()

{

    int fd,i;

    char mamname[20],s[100];

    unsigned char *ptr;

    printf(“\nEnter the shared memory name: “);

   scanf(“%s”,memname);

   fd=shm_open(memname,O_CREAT,S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH);

   ptr=mmap(NULL,100,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);

   if(fd>0)

   {

    printf(“\nEnter data:”);

   gets(s);

   for(i=0;s[i]!=’\0’;i++)

    *(ptr+i)=s[i];

}

Shell programs for prime and palindrome

Shell scripting programs to implement whether a number is prime as well as a program to check for a palindrome. If you have any doubts please let me know 

PRIME

#!/bin/bash
echo " enter a number"
read n
i=2
flag=0
while((i<=$n/2))
do

((c = n % i))
if ((c==0))
then
flag=1
fi
((i=i+1))
done
if ((flag==0))
then
echo "prime"
else
echo "composite"
fi

PALINDROME

echo “enter a string to be entered:”

read str

echo

len=`echo $str | wc –c`

len= ((len-1))

i=1

j= ((len/2))

while((i<j))

do

k=`echo $str | cut –c $i`

l=`echo $str | cut –c $len`

if((k!=l))

then

flag=1;

fi

((i=i+1))

((len=len-1))

Done

If((flag==0))

then

Echo “palindrome”

Else

Echo “ not palindrome”

fi    

Implementation of ls and grep

C programs for the implementation of ls and grep for the operating systems lab. If you have any doubts, please let me know.

ls

#include<stdio.h>

#include<dirent.h>

main(int argc, char ** argv)

{

    DIR *dp;

    struct dirent *link;

    dp=opendir(argv[1]);

    printf("\n the contents of directory %s are \n",argv[1]);

     while((link==readdir(dp))!=0)

     printf("%s",link->d_name);

      closedir(dp);

}

GREP

#include<stdio.h>

#include<string.h>

#define max 1024

void usage()

{

   printf("usage:\t./a.out filename word\n");

}

int main(int argc, char *argv[])

{

   FILE *fp;

   char fline[max];

   int count=0;

   int occurrences=0;

   if(argc!=3)

   {

     usage();

      exit(1);

   }

   if(!(fp=fopen(argv[1],"r")))

   {

      printf("grep : could not open file: %s\n",argv[1]);

       exit(1);

   }

   while(fgets(fline,max,fp)!=NULL)

    {

        count++;

         if(newline=strchr(fline,'\n'))

         *newline='\0';

         if(strchr(fline,argv[2]!=NULL)

          {

              printf("%s: %d %s\n",argv[1],count,fline);

              occurrences++;

          }

      }

}

Program for Best Fit, Worst Fit and First Fit

This is a program for the implementation of Best fit, Worst Fit, and First Fit for the operating systems lab. If you have any doubts please let me know.

#include<stdio.h>

#include<stdlib.h>

int i,j,n,x,ch,size,ch1,ch2,y,pid;

struct alloc1

{

  int id,sa,ea,size;

  struct alloc1 *next;

}*start=NULL,*ptr=NULL,*newn=NULL;

struct free1

{

  int stadd,eadd,size1;

  struct free1 *next;

}*start1=NULL,*newn1=NULL,*ptr2=NULL,*preptr2=NULL;

void displayfree(struct free1 *temp)

{

printf("\n\nFree Space\n");

temp=start1;

while(temp!=NULL)

    {

    printf("%d",temp->stadd);

    printf(" - %d\n",temp->eadd);

    temp=temp->next;

    }}

void display(struct alloc1 *temp1)

{

printf("\n\nAllocated\n");

temp1=start;

while(temp1!=NULL)

    {

                        printf("p%d\t",temp1->id);

    printf("%d",temp1->sa);

    printf(" - %d\n",temp1->ea);

    temp1=temp1->next;

    }

}

void init()

{

   newn->sa=ptr2->stadd;

   newn->ea=newn->sa+size-1;

   ptr2->stadd=ptr2->stadd+size;

   ptr2->size1=ptr2->size1-size;

}

void main()

{

    printf("\nEnter the number of processes:\n");

  scanf("%d",&n);

   for(i=0;i<n;i++)

  {

         newn=(struct alloc1 *) malloc(sizeof(struct alloc1));

         printf("\nEnter process id: ");

         scanf("%d",&newn->id);

         printf("\nEnter the start address: ");

         scanf("%d",&newn->sa);

         printf("\nEnter the end address: ");

         scanf("%d",&newn->ea);

         newn->size=(newn->ea-newn->sa)+1;

         if(start==NULL)

        {

            start=newn;

            start->next=NULL;

            ptr=start;

        }

       else

       {

            while(ptr->next!=NULL)

            {

            ptr=ptr->next;

            }

            ptr->next=newn;

            ptr=ptr->next;

            ptr->next=NULL;

       }

}

 printf("\nEnter the details of free space\n");

 do

 {

    newn1=(struct free1 *) malloc(sizeof(struct free1));

   printf("\nEnter the starting address: ");

   scanf("%d",&newn1->stadd);

   printf("\nEnter the ending address: ");

   scanf("%d",&newn1->eadd);

   newn1->size1=(newn1->eadd-newn1->stadd)+1;

    if(start1==NULL)

  {

    start1=newn1;

    start1->next=NULL;

  ptr2=start1;

   }

   else

   {

     while(ptr2->next!=NULL)

       ptr2=ptr2->next;

     ptr2->next=newn1;

     ptr2=ptr2->next;

     ptr2->next=NULL;

  }

  ptr2=start1;

  printf("\nPress 1 to add more...");

  scanf("%d",&ch);

 }while(ch==1);

printf("\n BEFORE FITTING\n");

displayfree(ptr2);

 ptr=start;

display(ptr);

do

{

  printf("\nEnter the size of new process: ");

  scanf("%d",&size);

  printf("\nEnter the process id:");

  scanf("%d",&pid);

 newn=((struct alloc1 *)malloc(sizeof(struct alloc1)));

   newn->next=NULL;  

   newn->size=size;

               newn->id=pid;

     printf("\nMENU:\n1.First fit\n2.Best fit\n3.Worst fit\n4.Exit\n");

     printf("\nEnter your choice:\n");

     scanf("%d",&ch1);

     switch(ch1)

     {

       case 1:

   ptr2=start1;

   if(ptr2->size1==size)

   {

   start1=ptr2->next;

   }

   else

   {

   while(ptr2->size1<size)

   {

    if(ptr2->next==NULL)

     {

        printf("\nInsufficient memory");

  goto lab;

      }

   preptr2=ptr2;

   ptr2=ptr2->next;

   if(ptr->size==size)

   {

   preptr2->next=ptr2->next;

   }}}

   init(); ptr=start;

while(ptr->next!=NULL)

   ptr=ptr->next;

      ptr->next=newn;

   printf("\nFIRST FIT\n");

   display(ptr);

   displayfree(ptr2);

          lab: break;

case 2:

   ptr2=start1;

   x=1000;

   while(ptr2!=NULL)

   {

   if((ptr2->size1>=size)&&(ptr2->size1<=x))

   {

   x=ptr2->size1;

   }

   ptr2=ptr2->next;

  }

  if(x==1000)

  {

   printf("\nInsufficient memory");

  break;

  }

   ptr2=start1;

   while(ptr2->size1!=x)

   {

   preptr2=ptr2;

   ptr2=ptr2->next;

   }

init();

if(x==size)

   preptr2->next=ptr2->next;

   ptr=start;

   while(ptr->next!=NULL)

   ptr=ptr->next;

   ptr->next=newn;

   printf("\nBEST FIT\n");

   display(ptr);

   displayfree(ptr2);

break;

case 3:   

   ptr2=start1;

       y=0;

   while(ptr2!=NULL)

   {

   if((ptr2->size1>=size)&&(ptr2->size1>=y))

   {

   y=ptr2->size1;

   }

   ptr2=ptr2->next;

  }

if(y==0)

   {

   printf("\nInsufficient memory");

  break;

   }

   ptr2=start1;

   while(ptr2->size1!=y)

   {

   preptr2=ptr2;

   ptr2=ptr2->next;

   }

   if(y==size)

   {

   preptr2->next=ptr2->next;

   }

   init(); ptr=start;

   while(ptr->next!=NULL)

   {

   ptr=ptr->next;

   }

   ptr->next=newn;

  printf("\nWORST FIT\n");

   display(ptr);

   displayfree(ptr2);

   break;

case 4:break;

default:break;

}

printf("\npress 1 to add more..");

scanf("%d",&ch2);

}while(ch2==1);

}