Linear search not working for large data set

I have a text file of the form:
number string

I want to be able to search for a code using binary search, look up a specific name using linear search and print all names that start with a specific word.

Code:

---

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


#define MAXLINESIZE 300


typedef struct{
    int code;
    char *name;
}JOB;


int countLines(FILE *fp)
{
    int count = 0;
    for (int c; (c = fgetc(fp)) != EOF; )
        if (c == '\n')
            ++count;
    return count;
}


int binarySearch(JOB *arr, int l, int r, int x)
{
    if (r >= l) {
        int mid = l + (r - l) / 2;
 
        if (arr[mid].code == x)
            return mid;
 
        if (arr[mid].code > x)
            return binarySearch(arr, l, mid - 1, x);
 
        return binarySearch(arr, mid + 1, r, x);
    }
 
    return -1;
}


int linearSearch(JOB *arr, int n, char *x)
{
    int i;
    for (i = 0; i < n; i++)
    {
        if (strcmp(arr[i].name, x) == 0)
        {
            return i;
        }
    }


    return -1;
}


bool StartsWith(const char *a, const char *b)
{
    if(strncmp(a, b, strlen(b)) == 0)
        return 1;
    return 0;
}




void linearSearchStart(JOB *arr, int n, char *x)
{
    int i;
    bool found = false;
    for (i = 0; i < n; i++)
    {
        if (StartsWith(arr[i].name, x) == 1)
        {
            found = true;
            printf("[%02d]  Code: %d\t | Job: %s\n", i+1, arr[i].code, arr[i].name);
        }
    }
    if(!found)
        printf("NOT found\n");
}




int main(int argc, char **argv)
{
    FILE *fin = fopen("search_file2.txt", "r");
   
    if(!fin)
    {
        fprintf(stderr, "Error opening the file.\n");
        exit(EXIT_FAILURE);
    }


    int nEntries = countLines(fin);
    fseek(fin, 0L, SEEK_SET);
    //printf("%d", nEntries);
    JOB *arr = (JOB *)malloc(nEntries * sizeof(JOB));
    int k;
    char buf[MAXLINESIZE];
    while(!feof(fin))
    {
        fscanf(fin, "%d", &arr[k].code);
        fgetc(fin);
        if(fgets(buf, sizeof(buf), fin) != NULL)
        {
            buf[strlen(buf) - 1] = '\0';
            arr[k].name = strdup(buf);
            k++;
        }
    }


    printf("%d\n", k);


    for(k = 0; k < nEntries; k++)
    {
        printf("[%d]  Code : %d\t | Job: %s\n", k+1, arr[k].code, arr[k].name);
    }


    int x = 111107;
    char *y = "senator";
    char *z = "president";
    int search = binarySearch(arr, 0, nEntries-1, x);
    int lin_search = linearSearch(arr, nEntries, y);


    if(search != -1)
    {
        printf("Element %d found at line %d\n", x, search + 1);
        printf("[%d]  Code: %d\t | Job: %s\n", search + 1, arr[search].code, arr[search].name);
    }
    else
    {
        printf("Element %d was NOT found in the given set\n", x);
    }


    if(lin_search != -1)
    {
        printf("Job %s found at line %d\n", y, lin_search + 1);
        printf("[%d]  Code: %d\t | Job: %s\n", lin_search + 1, arr[lin_search].code, arr[lin_search].name);
    }
    else
    {
        printf("Job %s was NOT found in the given set\n", y);
    }


    linearSearchStart(arr, nEntries, z);


    fclose(fin);
    return 0;
}

---

For the text file:
111102 ambasador
111107 senator
111108 governor
111111 president
111121 prime minister

Output:
5
[1] Code : 111102 | Job: ambasador
[2] Code : 111107 | Job: senator
[3] Code : 111108 | Job: governor
[4] Code : 111111 | Job: president
[5] Code : 111121 | Job: prime minister
Element 111107 found at line 2
[2] Code: 111107 | Job: senator
Job senator found at line 2
[2] Code: 111107 | Job: senator
[04] Code: 111111 | Job: president


Which is perfect, however, if I add 4000 more entries to this file, linear search will not work anymore, so if I were to search for 'senator' again, it will not find it, even though it is on the exact same line as before. Why is this happening?

I notice that you forgot to initialize k to 0 before filling your jobs array (which would be better named "jobs" instead of the meaningless "arr"). You are also not testing for end-of-file correctly. Perhaps something like this:

Code:

---

    for (int i = 0; fscanf(fin, "%d", &jobs[i].code) == 1; ++i)
    {
        char buf[MAXLINESIZE];
        fgetc(fin);
        if (fgets(buf, sizeof buf, fin) != NULL)
        {
            buf[strlen(buf) - 1] = '\0';
            jobs[i].name = strdup(buf);
        }
    }

---

And although it is not strictly necessary in this case, it is always best to free the memory you malloc at some point.

Thank you! I know !while(feof) is considered a bad practice, so your solution is way more elegant. But I still have the same problem, if I search for a specific job using linear search in a text file with 20 lines it finds it, but it doesn't if the file has 4000 lines. I don't understand why. I have a file with 4238 lines, I checked the values for k and nEntries and they are both 4238, so I have no idea why this is happening

In the 4238-line file, make sure that there is not an extra space before or after the word senator.