How to update struct text file line by line-CodePudding

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?

CodePudding user response：

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);

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

for a 5 byte buffer.

CodePudding user response：

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);
    }
}