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My code store all activities details in a file and I have problem accessing data in that file by searching using id. This is my add activities function and struct.

struct activities{
    char id[5];
    char actName[200];
    char date[20];
    char day[20];
}act;

//function to add volunteering activities
void addAct(){
    FILE *fileAct;
    
    //prompt user to enter activities details
    printf("\n\t Planning Volunteering Activities");
    printf("\n\t -----------------------------------");
    printf("\n\t Program ID \t: ");
    scanf(" %[^\n]%*c", &act.id);
    printf("\t Name of Activity : ");
    scanf(" %[^\n]%*c", &act.actName);
    printf("\t Date \t\t: ");
    scanf(" %[^\n]%*c", &act.date);
    printf("\t Day \t\t: ");
    scanf(" %[^\n]%*c", &act.day);
    
    //create & write in file activity
    fileAct = fopen("Activity", "a");
    
    fprintf(fileAct, "\n\t %s \n", act.id);
    fprintf(fileAct, "1. Name of Activity : %s \n", act.actName);
    fprintf(fileAct, "2. Date : %s \n", act.date);
    fprintf(fileAct, "3. Day : %s \n", act.day);
    
    //close file activity
    fclose(fileAct);
}

And this is my update function.

void updateAct(){
    //variable declaration
    char progID[5];
    
    //open activity file
    FILE *fp = fopen ("Activity", "r");
    
    //prompt user to search activities to update
    printf("\t Search by Program ID : ");
    scanf(" %[^\n]%*c", &progID);
   
    while( !feof(fp)){
        fread (&act, sizeof(struct activities), 1, fp);
        
        if (strcmp(progID, act.id) == 0)
            printf("%s %s", act.id, act.actName);
    }
    fclose(fp);
}

In the update function above, I couldnt access the act.id in struct based on user search, instead, the program display the whole data in the file. How can fix this problem?

penguinsoo
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  • Please provide information: What is the actual output, what is the desired output, how does the input look like. – Sinic Jan 02 '22 at 17:06
  • Beware: [`while (!feof(...))`](https://stackoverflow.com/q/5431941/3545273) is wrong and lead to processing the last record twice... – Serge Ballesta Jan 02 '22 at 17:11
  • The user will input the id, then the program should display all information of activities with that id only. But, for my code, the program display all data in that particular file although I try to display act.id only. – penguinsoo Jan 02 '22 at 17:14
  • @SergeBallesta can you guide me on what to replace the while statement? – penguinsoo Jan 02 '22 at 17:17
  • @penguinsoo: The link I gave should explain everything... (far better that what I could write) – Serge Ballesta Jan 02 '22 at 17:20

2 Answers2

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You provide pointers to char arrays, which technically is a pointer to a pointer. But scanf only needs pointers.

Remove the &'s of the scanf()-calls and add a maximum lengt specifier to your format arguments:

Change

scanf(" %[^\n]%*c", &progID);

to

scanf(" %4[^\n]%*c", progID);

for a 5 byte buffer.

Sinic
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  • Okay I've tried this, but can you guide me on how to access data in files that match the id that user prompt? – penguinsoo Jan 02 '22 at 16:34
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void readLine(char* message, char* buffer, int buffer_size)
{
    printf("\t%s: ", message);
    fgets(buffer, buffer_size, stdin);
    // fgets inserts '\n' at the end
    // we are removing it
    buffer[strlen(buffer) - 1] = '\0'; 
}

void addAct(){
    FILE *fileAct;
    struct activities newAct;
    //prompt user to enter activities details
    printf("\n\tPlanning Volunteering Activities");
    printf("\n\t-----------------------------------\n");

    readLine("Program ID", newAct.id, sizeof(newAct.id));
    readLine("Name of Activity", newAct.actName, sizeof(newAct.actName));
    readLine("Date", newAct.date, sizeof(newAct.date));
    readLine("Day", newAct.day, sizeof(newAct.day));

    //create & write in file activity
    fileAct = fopen("Activity", "ab+");
    if(NULL != fileAct) {
        fwrite(&newAct, sizeof(struct activities), 1, fileAct);
        //close file activity
        fclose(fileAct);
    }
}

void updateAct(){
    //variable declaration
    char progID[5];
    struct activities readAct;
    //open activity file
    FILE *fp = fopen("Activity", "rb");
    if(NULL != fp) {
        //prompt user to search activities to update
        printf("\tSearch by Program ID : ");
        fgets(progID, sizeof(progID), stdin);
        progID[strlen(progID) - 1] = '\0';
        while(fread(&readAct, sizeof(struct activities), 1, fp) != 0){
            if (strcmp(progID, readAct.id) == 0)
            {
                printf("%s %s\n", readAct.id, readAct.actName);
                break;
            }
        }
        fclose(fp);
    }
}
Larcis
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