Searching a name in a text file by ID - c

Question

I have a text file with 2 lines in it:
Voicu;Catalin;1234;2.32
Diana;Cadar;2345;1.01
I'm trying to make my program search in .txt file the ID (1234 or 2345) and match it to the name. Below is the code I've tried to make, but it won't find the ID in .txt after I write it in first scanf, the first thing that appears is the "else" line.
void alegereStudent(struct student *stud)
{
FILE *scStudenti = fopen("studenti.txt", "a");
char *error;
int i=0,n;
if(scStudenti==NULL)
{
error = strerror(errno);
printf("Fisierul nu poate fi creat: \n %s", error);
}
printf("\nIntroduceti Numele: ");
scanf("%39s", stud->numeStudent);
printf("Introduceti Prenumele: ");
scanf("%39s", stud->prenumeStudent);
printf("Introduceti ID-ul studentului: ");
scanf("%d", &stud->idStudent);
printf("Introduceti Media de admitere: ");
scanf("%f", &stud->medieAdmitere);
fprintf(scStudenti,"<%s>;", stud->numeStudent);
fprintf(scStudenti,"<%s>;", stud->prenumeStudent);
fprintf(scStudenti,"<%d>;", stud->idStudent);
fprintf(scStudenti,"<%.2f>\n", stud->medieAdmitere);
fclose(scStudenti);
}
//
void optiunea_2()
{
printf("\n1.Despre studenti.\n");
printf("2.Despre profesori.\n");
printf("3.Revenire la meniu principal.\n");
printf("\nAlegeti o optiune: ");
scanf("%d",&alegere_opt2);
switch(alegere_opt2)
{
case 1: while(&stud!=NULL)
{
FILE *scStudenti = fopen("studenti.txt", "r");
char *error;
int cautareID;
if(scStudenti==NULL)
{
error = strerror(errno);
printf("Fisierul nu poate fi creat: \n %s", error);
}
printf("\nIntroduceti ID-ul studentului: ");
scanf("%d", &cautareID);
fscanf(scStudenti,"%d",&stud->idStudent);
if(cautareID==&stud->idStudent)
{
printf("Numele Studentului este %s %s",&stud->numeStudent, &stud->prenumeStudent);
}
else
printf("\nAcest ID nu exista!\n");
optiunea_2();
}break;

Answer 1

fprintf(scStudenti,"<%s>;", stud->numeStudent);
fprintf(scStudenti,"<%s>;", stud->prenumeStudent);
fprintf(scStudenti,"<%d>;", stud->idStudent);
fprintf(scStudenti,"<%.2f>\n", stud->medieAdmitere);
fclose(scStudenti);
This makes formatting much more difficult. The output file will contain:
<first>;<last>;<1234>;<0.5>
You want to start with a new file and simplify the output to write:
first;last;1234;0.5
Don't always put & in front of integer. Just use:
if(cautareID == stud->idStudent)
{
...
}
Example:
const char *filename = "studenti.txt";
void alegereStudent()
{
struct student stud;
FILE *scStudenti = fopen(filename, "a");
if(scStudenti == NULL)
{
printf("error\n");
return;
}
printf("\nIntroduceti Numele: ");
scanf("%39s", stud.numeStudent);
printf("Introduceti Prenumele: ");
scanf("%39s", stud.prenumeStudent);
printf("Introduceti ID-ul studentului: ");
scanf("%d", &stud.idStudent);
printf("Introduceti Media de admitere: ");
scanf("%f", &stud.medieAdmitere);
fprintf(scStudenti, "%s;", stud.numeStudent);
fprintf(scStudenti, "%s;", stud.prenumeStudent);
fprintf(scStudenti, "%d;", stud.idStudent);
fprintf(scStudenti, "%.2f\n", stud.medieAdmitere);
fclose(scStudenti);
}
void find_by_id(int id)
{
FILE *fin = fopen(filename, "r");
if(!fin)
return;
int count = 0;
struct student stud;
while(fscanf(fin, "%39[^;];%39[^;];%d;%f\n",
stud.numeStudent, stud.prenumeStudent, &stud.idStudent, &stud.medieAdmitere) == 4)
{
if(id == stud.idStudent)
{
printf("found %s %s\n", stud.numeStudent, stud.prenumeStudent);
}
count++;
}
if(count == 0)
printf("failed to read any record. Start with a new file.\n");
}
int main(void)
{
alegereStudent();
find_by_id(1234);
return 0;
}
If <> characters are added, then read according to that format, you then have to remove the extra <> characters from the string.
void alegereStudent()
{
struct student stud;
...
fprintf(scStudenti, "<%s>;", stud.numeStudent);
fprintf(scStudenti, "<%s>;", stud.prenumeStudent);
fprintf(scStudenti, "<%d>;", stud.idStudent);
fprintf(scStudenti, "<%.2f>\n", stud.medieAdmitere);
fclose(scStudenti);
}
void find_by_id(int id)
{
...
struct student stud;
while(fscanf(fin, "%39[^;];%39[^;];<%d>;<%f>\n",
stud.numeStudent, stud.prenumeStudent, &stud.idStudent, &stud.medieAdmitere) == 4)
{
if(id == stud.idStudent)
{
char *p;
size_t i;
//remove the extra <> characters
p = stud.numeStudent;
if (strlen(p) > 1)
{
for(i = 1; i < strlen(p) - 1; i++)
p[i - 1] = p[i];
p[i - 1] = 0;
}
//remove the extra <> characters
p = stud.prenumeStudent;
if (strlen(p) > 1)
{
for(i = 1; i < strlen(p) - 1; i++)
p[i - 1] = p[i];
p[i - 1] = 0;
}
printf("found %s %s\n", stud.numeStudent, stud.prenumeStudent);
}
count++;
}
if(count == 0)
printf("failed to read any record. Start with a new file.\n");
}

Answer 2

#include <stdlib.h>
#include <stdio.h>
int main(void)
{
char const *filename = "test.txt";
FILE *input = fopen(filename, "r");
if (!input) {
fprintf(stderr, "Couldn't open \"%s\" for reading!\n\n", filename);
return EXIT_FAILURE;
}
char name[101];
char surname[101];
int id;
double value;
while (fscanf(input, "%100[^;];%100[^;];%d;%lf%*[\n]", name, surname, &id, &value) == 4) {
if (id == 2345) {
printf("Found \"%s %s\" by id %d\n\n", name, surname, id);
break;
}
}
}