如何从文本文件的一行中读取某些信息？

Question

I'm trying to read the CIN code for patients between 1997 and 2000 dates from file patient.txt . It mostly works well but in the specific 1981 date, which there are two of patients with this same date, it seems to display only the CIN code for the first patient, Why is that?

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

void main()
{ 
    FILE *fichier;
    fichier = fopen("patient.txt", "w");
    if (fichier != NULL) printf("le fichie patient.txt est cree !\n");
    fprintf(fichier, "voici la liste de nos patients!\n");
    fprintf(fichier, "nom:Tahar prenom:Jaafer CIN:14610862 Date De Naissance:14/01/2002\n");
    fprintf(fichier, "nom:Ali prenom:Khalfalh CIN:26540392 Date De Naissance:15/02/1997\n");
    fprintf(fichier, "nom:Mohamed prenom:Gamadi CIN:15401256 Date De Naissance:12/12/2000\n");
    fprintf(fichier, "nom:Samir prenom:Alouani CIN:11226508 Date De Naissance:7/02/1981\n");
    fprintf(fichier, "nom:Haj prenom:Mohamed ali CIN:12012725 Date De Naissance:15/05/2005\n");
    fprintf(fichier, "nom:Farah prenom:Bouanane CIN:12751802 Date De Naissance:18/07/1981\n");
    fclose(fichier);
    char sntnc[100];
    int pos;
    char *ptr1[50], *ptr2[50];
    fichier = fopen("patient.txt", "r");
    char word[8] = "/1981\n", nm_cin[5];
    int c;
    while ((c = getc(fichier)) != EOF)
    {fgets(sntnc, 100, fichier);
        if (strstr(sntnc, word) != 0)
        {printf("found\n");
            *ptr1 = strstr(sntnc, "CIN");
            *ptr2 = strstr(sntnc, "\n");
            pos = (*ptr1 - *ptr2) + 2;
            fseek(fichier, pos, SEEK_CUR);
            fscanf(fichier, "%s", nm_cin);
            printf("CIN=%s\n", nm_cin);
        }
    }
}

Answer 1

There are two major errors.

1. nm_cin[5] - The array is too short to store the 8-digit CIN. The fscanf() stores beyond the end of the array, overwrites another variable, and the program ceases to behave well-defined. Make it nm_cin[9] .

2. After fseek() and fscanf() the file position is in the middle of the line and the next fgets() continues reading from there. This causes the program to get out of step. Better don't disturb the read sequence. You already have the whole line read as a string , as Weather Vane noted, so you can read the CIN from the sntnc buffer. Change

    pos = (*ptr1 - *ptr2) + 2; fseek(fichier, pos, SEEK_CUR); fscanf(fichier, "%s", nm_cin);

   to

    sscanf(*ptr1+4, "%8s", nm_cin);