Thread: input the number of the line you want to print - Text File

The code is working nice for me.


But feel free to give me advice.

Code:

#include <stdio.h>
#include <stdlib.h>
#define SIZE 100


int main(int argc, char** argv) {


    FILE * pFile;


    char buffer[SIZE];


    if ((pFile = fopen("code.txt", "rt")) == NULL) {
        return -1;
    }


    int nrline_to_printf = 0;
    int nrline_on_the_file = 0;


    puts("What line you want to print ? (put a number)");
    scanf("%d", &nrline_to_printf);


    while (fgets(buffer, sizeof (buffer), pFile) != NULL) {
        if (nrline_to_printf == nrline_on_the_file) {
            fputs(buffer, stdout);
            return (EXIT_SUCCESS);
        }
        nrline_on_the_file++;
    }


    puts("That line does not exist");
    return (EXIT_SUCCESS);


}

A normal, non-programmer counts from one to some upper limit. A C Programmer counts from ZERO to some upper limit. You need to make sure you both are talking about the same line number! I leave it to you to figure out this simple change, and how to inform the user if the first line is one or zero!

Originally Posted by thinkabout

int count_lines(FILE * pFile, int nrlines_of_the_file, char * buffer) .... // i am doing something wrong, it says my file have 11 lines but in reality the file have 4 lines.

How long is each line in the file? If any line is longer than 99 characters (including the line terminator), then it will take more than one fgets() call to read the entire line, and it will be counted as more than one line. You could change count_lines() to increment nrlines_of_the_file only when the string read by fgets() ends in a line terminator (\n).

I see, i din´t know how to pass the strings, and no one teach me about size_t.

I know i can use int bufsize, but i think the correct way is to use size_t (for sure a positive value).

Why size_t matters | Embedded . - A little to advanced for me.

size_t - C++ Reference

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define SIZE 100


int count_lines(FILE * pFile, char *buffer, size_t bufsize, int nrlines_of_the_file);
int ask_user_input(int nrline_to_printf, int nrlines_of_the_file);
int printf_the_line(FILE * pFile, char *buffer, size_t bufsize, int nrline_to_printf);


int main(int argc, char** argv) {


    char buffer[SIZE];
    FILE * pFile;


    if ((pFile = fopen("code.txt", "rt")) == NULL)
        return -1;


    int nrlines_of_the_file = 0;
    int nrline_to_printf = 0;


    // The file have at least one line
    nrlines_of_the_file = count_lines(pFile, buffer, sizeof (buffer), nrlines_of_the_file);
    nrline_to_printf = ask_user_input(nrline_to_printf, nrlines_of_the_file);
    printf_the_line(pFile, buffer, sizeof (buffer), nrline_to_printf);


    return (EXIT_SUCCESS);


}


int count_lines(FILE * pFile, char *buffer, size_t bufsize, int nrlines_of_the_file) {


    while (fgets(buffer, bufsize, pFile) != NULL) {
        if (buffer[strlen(buffer) - 1] == '\n') {
            nrlines_of_the_file++;
        } else if (feof(pFile)) { // only happens at end of file when last line doesn't have \n - user forgets to press "Enter"
            nrlines_of_the_file++;
        }
    }
    rewind(pFile);


    return nrlines_of_the_file;
}


int ask_user_input(int nrline_to_printf, int nrlines_of_the_file) {


    do {
        printf("What line you want to print ?\n(put a number between 1 and %d)\n", nrlines_of_the_file);
        scanf("%d", &nrline_to_printf);
    } while (nrline_to_printf < 1 || nrline_to_printf > nrlines_of_the_file);


    return nrline_to_printf;


}


int printf_the_line(FILE * pFile, char *buffer, size_t bufsize, int nrline_to_printf) {


    int nrline_on_the_file = 0;


    while (fgets(buffer, bufsize, pFile) != NULL) {
        if (nrline_to_printf == nrline_on_the_file + 1) {
            fputs(buffer, stdout);
            return (EXIT_SUCCESS);
        }
        nrline_on_the_file++;
    }
    return 0;
}