在 C 中的文件中添加行号

Question

I am trying to master working with files in C, and I have a bump which I can't pass. I have been searching all day for information but I can't seem to find what I am looking for. I would like to number the lines in a file. For example, if I type in information about a book (let's say: Name, Air-date and id), I would expect something like this in my file:

1. Name:Dave Air-Date:1997 id:123

And I would like this to update itself. Say I close the program and run it again, the counting should start from 2.

My only problem is numbering the lines. Could someone point me in the right direction how to do this, or show me a sample source code?

Answer 1

You could process each character one by one, and increment a counter that you print before the character when you encounter a carriage return ( \\n ).

In pseudo-code:

lineNumber = 1;
Open the file
While ((c = read a character) is not EOF)
    If (c is \n)
        Print "lineNumber", then increment it
    Print c
End while
Close the file

Answer 2

It's too late, but I hope it helps.

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

int main() {
  /* user input */
  char text[50];
  char res[100] = "";
  printf("Enter a short story (<100 characters): ");
  char ch;
  char *ptr = text;
  while ((ch = getchar()) != EOF) {
    *ptr++ = ch;
  }
  printf("\nYou've entered this text:\n");
  printf("%s\n", text);

  /* append and create a new text */
  strcat(res, "0: ");
  char *qtr = text;
  int i = 1;
  while (*qtr != '\0') {
    if (*qtr != '\n') {
      char temp[2];
      sprintf(temp, "%c", *qtr);
      strcat(res, temp);
    } else {
      char temp[5];
      sprintf(temp, "\n%d: ", i++);
      strcat(res, temp);
    }
    qtr++;
  }

  printf("\nLine number added: \n");
  printf("%s\n", res);

  return 0;
}