typeline

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <string.h>

char cmd[200];
char tokenOne[20];
char tokenTwo[20];
char tokenThree[20];
char tokenFour[20];

int numberOfTokens = 0;

int main(void)
{
void typeline(char *,char *);

while(1)
{
	printf("MyShell $] ");
	fgets(cmd,sizeof(cmd),stdin);

	numberOfTokens = sscanf(cmd,"%s%s%s%s",tokenOne,tokenTwo,tokenThree,tokenFour);

	

	switch(numberOfTokens)
	{
		case 1:
			if(fork() == 0)
			{
				execlp(tokenOne,tokenOne,NULL);
			}
			wait(0);
			break;

		case 2:
			if(fork() == 0)
			{
				execlp(tokenOne,tokenOne,tokenTwo,NULL);
			}
			wait(0);
			break;

		case 3:
			if(strcmp(tokenOne,"typeline") == 0)
			{
				typeline(tokenTwo,tokenThree);
			}
			if(fork() == 0)
			{
				execlp(tokenOne,tokenOne,tokenTwo,tokenThree,NULL);
			}
			wait(0);
			break;

		case 4:
			if(fork() == 0)
			{
				execlp(tokenOne,tokenOne,tokenTwo,tokenThree,tokenFour,NULL);
			}
			wait(0);
			break;
	}

	if(( strcmp(tokenOne,"exit") == 0 ) && (numberOfTokens == 1))
	{
		        break;
	}


}

return(0);

}

void typeline(char *option,char *fname)
{
int lineCount = 0;

char ch = '\0';

int handle = 0;

int lineNumber = 0;

int numberOne = 0;

handle = open(fname,O_RDONLY);

if(handle == -1)
{
	printf("Error While Opening '%s' File !!!\n",fname);
	return;
}

lineNumber = atoi(option);

while(read(handle,&ch,1))
{
	if(ch == '\n')
	{
		lineCount++;
	}
}

if(strcmp(option,"a") == 0)
{
	lseek(handle,SEEK_SET,0);
	
	printf("\nDisplaying All Lines Of '%s' File\n\n",fname);

	while(read(handle,&ch,1))
	{
		printf("%c",ch);
	}

	printf("\n-----------------------------------------------------------------------\n");

}
else if(lineNumber >= 0)
{
	lseek(handle,SEEK_SET,0);

	printf("\nDisplaying %d Lines Of '%s' File \n\n",lineNumber,fname);

	while(read(handle,&ch,1))
	{
		if(ch == '\n')
		{
			numberOne++;
		}

		if(numberOne == lineNumber)
		{
			break;
		}

		printf("%c",ch);

	}

	printf("\n-----------------------------------------------------------------------\n");
}
else if(lineNumber < 0)
{
	lseek(handle,SEEK_SET,0);

	printf("\nDisplaying Last %d Lines Of '%s' File\n\n",-lineNumber,fname);

	numberOne = 0;

	lineCount = lineCount + lineNumber;

	while(read(handle,&ch,1))
	{
		if(ch == '\n')
		{
			numberOne++;
		}

		if(numberOne == lineCount)
		{
			break;
		}
	}

	while(read(handle,&ch,1))
	{
		printf("%c",ch);
	}

	printf("\n-----------------------------------------------------------------------\n");

}

}