TYBcs OS-Syspro Slip 14-2 | IProgramX

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void make_toks(char *s, char *tok[])
{
int i=0;
char *p;

p = strtok(s," ");
while(p!=NULL)
{
tok[i++]=p;
p=strtok(NULL," ");
}

tok[i]=NULL;
}

void typeline(char *fn, char *op)
{
int fh,i,j,n;
char c;

fh = open(fn,O_RDONLY);
if(fh==-1)
{
printf("File %s not found.\n",fn);
return;
}

if(strcmp(op,"a")==0)
{
while(read(fh,&c,1)>0)
printf("%c",c);
close(fh);
return;
}

n = atoi(op);
if(n>0)
{
i=0;
while(read(fh,&c,1)>0)
{
printf("%c",c);
if(c=='\n') i++;
if(i==n) break;
}
}

if(n<0)
{
i=0;
while(read(fh,&c,1)>0)
{
if(c=='\n') i++;
}
lseek(fh,0,SEEK_SET);
j=0;
while(read(fh,&c,1)>0)
{
if(c=='\n') j++;
if(j==i+n) break;
}
while(read(fh,&c,1)>0)
{
printf("%c",c);
}
}

close(fh);
}

int main()
{
char buff[80],*args[10];
int pid;

while(1)
{
printf("myshell$");
fflush(stdin);
fgets(buff,80,stdin);
buff[strlen(buff)-1]='\0';
make_toks(buff,args);
if(strcmp(args[0],"typeline")==0)
typeline(args[2],args[1]);
else
{
pid = fork();
if(pid>0)
wait();
else
{
if(execvp(args[0],args)==-1)
printf("Bad command.\n");
}
}
}

return 0;
}