C Program To Print Lines From File

Below Given Is a Simple Program which prints the lines of a file but with different user given instructions.

The Feature of the Program is as Follows:

The Program Prints,

1) print first 10 lines of file

2) print last  20 lines of file

3) print all lines of file


#include <stdio.h>
#include <conio.h>
#include <process.h>
void main(int argc, char *argv[])
{
    int tot_lines,cnt;
    char *ptr;
    if( argc != 3 )
    {
        printf("\nInvalid number of arguments\n");
        return;
    }
    if( *argv[1] == '+' || *argv[1] == '-')
    {
        tot_lines = count_lines(argv[2]);
        ptr = argv[1];
        ptr++;  // skip '+' or '-'
        cnt = atoi(ptr);
        if ( cnt > tot_lines)
        {
            printf("\nInvalid line count\n");
            return;
        }
    }
    if( *argv[1] == '+' ) // typeline +cnt fname
        print_top_lines(argv[2],cnt);
    else
    if( *argv[1] == '-' ) // typeline -cnt fname
        print_bottom_lines(argv[2],cnt,tot_lines);
    else if (*argv[1]=='a')
        print_all_lines(argv[2]);
     else
         printf("\nInvalid option...");
} // main

int count_lines( char *fname)
{
    int tot_lines,ch;
    FILE *fp;
    char buff[80];
    fp = fopen(fname,"r");
    if( fp == NULL )
    {
        printf("\nUnable to open file");
        return(-1);
    }
    tot_lines = 0;
    while (fgets(buff,80,fp)!=NULL)
       tot_lines++;
    tot_lines++;
    fclose(fp);
    return(tot_lines);
} // count lines


int print_all_lines( char *fname)
{
    int ch;
    FILE *fp;
    char buff[80];
    fp = fopen(fname,"r");
    printf("\n");
    while(fgets(buff,80,fp)!=NULL)
     printf("%s",buff);

    fclose(fp);
    return;
} // print all lines

int print_top_lines(char *fname, int cnt)
{
    int curr_cnt;
    int ch;
    FILE *fp;
    char buff[80];

    curr_cnt = 0;

    fp = fopen(fname,"r");

    fgets(buff,80,fp);
    printf("\n");
    while( curr_cnt < cnt )
    {
        printf("%s",buff);
        fgets(buff,80,fp);
        curr_cnt++;
    }
    fclose(fp);
    return;
}
int print_bottom_lines(char *fname, int cnt, int tot_lines)
{
    int curr_cnt;
    int ch;
    FILE *fp;
    char buff[80];
    curr_cnt = 0;
    printf("\n");
    fp = fopen(fname,"r");
    while( 1)
    {
        fgets(buff,80,fp);
        curr_cnt++;
        if( curr_cnt >= tot_lines - cnt )
            break;
    }
    while( fgets(buff,80,fp) != NULL)
    {
        printf("%s", buff);
    }
    fclose(fp);
    return;
}