TYBcs OS-Syspro Slip 8-1 | IProgramX

#include<stdio.h>
#include<string.h>
#include<stdlib.h>

typedef struct node
{
char line[80];
struct node *next;
}NODE;

NODE *first,*last;
int len,changed;

NODE * get_node(char *s)
{
NODE *p;
p=(NODE*)malloc(sizeof(NODE));
strcpy(p->line,s);
p->next=NULL;
return p;
}

void create(char fname[])
{
NODE *p;
FILE *fp;
char buff[80];

fp = fopen(fname,"r");
if(fp==NULL)
{
printf("File %s not found.\n",fname);
exit(1);
}

while(fgets(buff,80,fp)!=NULL)
{
p = get_node(buff);

if(first==NULL)
first = p;
else
last->next = p;

last = p;
len++;
}

fclose(fp);
}

void append()
{
NODE *p;
char buff[80];

printf("Enter text (type END to stop):");

fflush(stdin);
fgets(buff,80,stdin);

while(strcmp(buff,"END\n")!=0)
{
p = get_node(buff);
if(first==NULL)
first = p;
else
last->next = p;
last=p;
len++;

fflush(stdin);
fgets(buff,80,stdin);
}

changed=1;
}

void save(char fname[])
{
FILE *fp;
NODE *p;

fp = fopen(fname,"w");

p = first;
while(p!=NULL)
{
fputs(p->line,fp);
p=p->next;
}

fclose(fp);
changed=0;
}

void del1(int pos)
{
NODE *p,*q;
int i=1;

p = q = first;
while(i<pos)
{
q = p;
p = p->next;
i++;
}

if(p==first)
{
first = p->next;
}
else if(p==last)
{
q->next=NULL;
last=q;
}
else
{
q->next=p->next;
}

free(p);
len--;
changed=1;
}

void del(int n1, int n2)
{
int n,i;
n=n2-n1+1;
for(i=1;i<=n;i++)
del1(n1);
}

int main(int argc, char *argv[])
{
char buff[80],ch,fname[30]="";
int n1,n2;

if(argc==2)
{
strcpy(fname,argv[1]);
create(fname);
}

while(1)
{
printf("$");
fflush(stdin);
fgets(buff,80,stdin);

sscanf(buff,"%c %d %d",&ch,&n1,&n2);

switch(ch)
{
case 'a':
append();
break;
case 's':
if(changed==1)
{
if(strlen(fname)==0)
{
printf("Enter source file name:");
fflush(stdin);
fgets(fname,30,stdin);
fname[strlen(fname)-1]='\0';
}
save(fname);
}
break;
case 'd':
if(n1>=1 && n2<=len && n1<=n2)
del(n1,n2);
else
printf("Invalid parameter\n");
break;
case 'e':
if(changed==1)
{
printf("Quit without save (Y/N)?");
fflush(stdin);
fgets(buff,80,stdin);
if(buff[0]=='N')
{
if(strlen(fname)==0)
{
printf("Enter file name:");
fflush(stdin);
fgets(fname,30,stdin);
fname[strlen(fname)-1]='\0';
}
save(fname);
}
}
exit(0);
default:
printf("Invalid command.\n");
}
}

return 0;
}