if my input is something similar to this:

4 2 3 5
2 3 5 1
3 7 8 1
6 8 1 4

and I would like to create an array with 4, 2, 3, and 6. How could I only read them from the file instead of reading the other numbers too? I would also like to sort them from smaller to bigger after that.

CodePudding user response：

You can write for example

fscanf( fp, "%d", &num );
for ( size_t i = 0; i < 3; i   ) fscanf( fp, "%*d" );

for each line of the text file.

To sort an array you can use standard C function qsort declared in the header <stdlib.h>.

CodePudding user response：

Best way is to use fgets to get each line, the sscanf to scan just the first value, like this:

FILE fp = fopen("testfile.txt","r");
char line[80];
int value;

if (!fp) {
    perror("opening file");
    exit(1);
}
if (!fgets(line,sizeof(line),fp)) {
    perror("reading file");
    exit(2);
}
sscanf(line," %d ",&value);

You'll probably want the fgets and sscanf in a loop to read the whole file.