CODEWITHSUNDEEP
carraysscanf
user3736742
user3736742

Reputation: 45

fscanf() only reads last integer per line

I am trying to use fscanf to read a file and store its contents in arrays. Each line contains four integer values, which need to be placed in four different arrays. My code reads each line, but stores the final integer value of each line in all four arrays.

I've tried using fgets(), which seemed to cause even more problems. Changing the format in the fscanf() call hasn't helped either.

Why is it skipping the first three values of each line?

code:

FILE *file;
int process_count, p_id[process_count], io_burst[process_count], priority[process_count], cpu_burst[process_count];

file = fopen(argv[1], "r");
if (!file) { error("File open failed"); }

process_count = atoi(argv[2]);

for (int i = 0; i < process_count; i++)
{
    if (fscanf(file, "%i %i %i %i", &p_id[i], &cpu_burst[i], &io_burst[i], &priority[i]) < 4)
    {
        error("File read failed");
    }

    printf("p_id: %i\n", p_id[i]);
    printf("cpu_burst: %i\n", cpu_burst[i]);
    printf("io_burst: %i\n", io_burst[i]);
    printf("priority: %i\n\n", priority[i]);
}

fclose(file);

input:

0           10           4           2
1            8           2           1
2           12           0           5
3            2           4           4
4            8           3           0
5            6           4           2
6            4           0           5
7           16           7           5
8           14           0           1
9            2          10           1

output:

p_id: 2
cpu_burst: 2
io_burst: 2
priority: 2

p_id: 1
cpu_burst: 1
io_burst: 1
priority: 1

p_id: 5
cpu_burst: 5
io_burst: 5
priority: 5

p_id: 4
cpu_burst: 4
io_burst: 4
priority: 4

p_id: 0
cpu_burst: 0
io_burst: 0
priority: 0

p_id: 2
cpu_burst: 2
io_burst: 2
priority: 2

p_id: 5
cpu_burst: 5
io_burst: 5
priority: 5

p_id: 5
cpu_burst: 5
io_burst: 5
priority: 5

p_id: 1
cpu_burst: 1
io_burst: 1
priority: 1

p_id: 1
cpu_burst: 1
io_burst: 1
priority: 1

Upvotes: 1

Views: 113

Answers (2)

M.M
M.M

Reputation: 141628

This is an error:

int process_count, p_id[process_count],

process_count is an uninitialized variable so it cannot be used for an array dimension (or anything else really).

To fix this you could change the code to:

int process_count = atoi(argv[2]);

if ( process_count < 1 )
    exit(EXIT_FAILURE);    // or similar

int p_id[process_count], io_burst[process_count], priority[process_count], cpu_burst[process_count];

Upvotes: 4

kaylum
kaylum

Reputation: 14046

You have undefined behaviour in your program.

int process_count, p_id[process_count], io_burst[process_count], cpu_burst[process_count];
...
process_count = atoi(argv[2]);

That code is using process_count before it has been intialised.

Upvotes: 2

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