Printf Function Printing More Parts Of Struct Array Than Intended

Question

Like the title says the portion of code

printf("%s", workers[0].first);

prints all the way up to the age part of the struct array, when I really just want it to print the "first" portion

in addition to that, I can't get the actual printWorkers() function to work (note that I have not set up the actual printing correctly inside that function, it is just a place holder)

this is the portion of .txt file it is reading

"ADA A AGUSTA 33 BABBAGE ROAD LOVELACE GB 19569 28 F 2 350.50"

The spaces don't appear the same in the above text as it does in the file.

The last thing I'm wondering is why a random character is being appended to the end of zip variable when it's printed out (not that I'm entirely sure it matters since it isn't supposed to print it)

It's also worth mentioning that because of my requirements the struct cannot be altered in any way.

#define _CRT_SECURE_NO_DEPRECATE
#include <stdio.h>
#include <stdlib.h>

#define MAX 100

FILE *fp;
FILE *fpIn;
FILE *fpOut;

typedef struct {
    char first[7];
    char initial[1];
    char last[9];
    char street[16];
    char city[11];
    char state[2];
    char zip[5];
    int age;
    char sex[1];
    int tenure;
    double salary;
    } payroll;

int readFile();
void strsub (char buf[], char sub[], int start, int end);
void printWorkers(int numOfWorkers);
payroll workers[MAX];

int main()
{
    int numOfWorkers = 0;


        if (!(fpIn = fopen("payfile.txt", "r")))
    {
        printf("payfile.txt could not be opened for input.");
        exit(1);
    }
    if (!(fpOut = fopen("csis.txt", "w")))
    {
        printf("csis.txt could not be opened for output.");
        exit(1);
    }

    readFile();
    numOfWorkers = readFile();
    printWorkers(numOfWorkers);

    printf("%s", workers[0].first);
    printf(" %d", workers[0].age);
    printf(" %s", workers[0].sex);
    printf(" %d", workers[0].tenure);
    printf(" %.2lf", workers[0].salary);


    return 0;
}


int readFile()
{
    int i = 0;
    char buf[MAX];
    while(!feof(fpIn))
    {

            fgets(buf, MAX, fpIn);
            strsub(buf, workers[i].first, 0, 6);
            strsub(buf, workers[i].initial, 8, 8);
            strsub(buf, workers[i].last, 9, 18);
            strsub(buf, workers[i].street, 19, 34);
            strsub(buf, workers[i].city, 36, 46);
            strsub(buf, workers[i].state, 48, 49);
            strsub(buf, workers[i].zip, 51, 56);
            sscanf(buf+58, "%2d", &workers[i].age);
            strsub(buf, workers[i].sex, 61, 61);
            sscanf(buf+63, "%d", &workers[i].tenure);
            sscanf(buf+65, "%lf", &workers[i].salary);

            ++i;

    }

    return i;
}

void strsub (char buf[], char sub[], int start, int end)
{
    int i, j;

    for (j=0, i=start; i <= end; i++, j++)
    {
        sub[j] = buf[i];
    }
    sub[j] = '\0';
}

void printWorkers(int numOfWorkers)
{
    int i;

    for (i = 0; i < numOfWorkers; i++)
    {
        printf("%7s %2s %10s %17s %12s %3s %6s %3d %2s %5d %.2lf\n",
                    workers[i].first, workers[i].initial, workers[i].last, workers[i].street, workers[i].city,
                    workers[i].state, workers[i].zip, workers[i].age, workers[i].sex, workers[i].tenure, workers[i].salary);
    }
}

Answer 1

You probably should take into account that printable strings are zero-byte terminated in C. Hence the fields in your anonymous struct should each have one more byte (so char first[8]; and char initial[2]; etc...). BTW the space for the last (family) name is really too small: my name won't fit in it, and is not that unusually wide.

You also should test the result of scanf & sscanf. They return the number of scanned items. You might use %5s to scan a field of 5 characters (+1 for the terminating zero byte). You should read the documentation of scanf before using it.

You should probably clear workers[i] e.g. with memset(workers+i, 0, sizeof(workers[i])); before filling it.

BTW, compile your program with all warnings & debug info (e.g. gcc -Wall -g if using GCC...) and use the debugger (e.g. gdb) e.g. to run it step by step.

Perhaps you should consider using pointers to the heap and C dynamic memory allocation. Then be sure to test against failure of malloc and beware of memory leaks; a tool like valgrind would be very helpful.

---

BTW, a printf call like printf("%s", workers[0].first); is having an undefined behavior (UB) when workers[0].first is a field or array of char-s which is not zero-byte terminated. And UB is really bad, you always should avoid it. Read Lattner's blog entries about undefined behavior.

Answer 2

Your code contains an undefined behavior. This function strsub(buf, workers[i].first, 0, 6) will write outside of array boundary:

void strsub (char buf[], char sub[], int start, int end)
{
    int i, j;

    for (j=0, i=start; i <= end; i++, j++)
    {
        sub[j] = buf[i];
    }
    sub[j] = '\0';
}

After the loop a j variable would be 7 and you will overwrite adjusted struct members. This is a root of your problems with the sprintf function and incorrect symbol output.

However the main problem is in your reading algorithm. You are taking parts of the fixed length from the input string. But different people have a names of different lengths. Lets consider your example

"ADA A AGUSTA 33 BABBAGE ROAD LOVELACE GB 19569 28 F 2 350.50"

firstName is expected to be ADA. Yet since you are taking fixed 7 characters from the string it will be ADA A A. Is a data sting dont have a sufficient length you will be reading outside its boundary which is an undefined behavior as well.