UNIX for Dummies Questions & Answers

hi there...
i have a question regarding the fscanf function...
let's say i have a data:
1 2 3 4 5 6
7 8 9 1 2 3
4 5 6 7 8 9
1 2 3 4 5 6

how do i read only the first COLUMN, or the second COLUMN or the third COLUMN or etc....??????
thanks

There's no graceful way to do it, it'd be better to read all 6 columns and just use the ones you need.

fscanf shouldn't be used for line-delimited data like this since if it encounters data that doesn't match what you want, it may stop halfway through the line, not to mention remaining there if the rest of the line doesn't match its command string. It's better to read line-by-line and process each line with sscanf, bad lines will just be skipped instead of plugging it up.

Code:

while(!feof(file))
{
    int var[6];
    char buf[512];
    if(fgets(buf, 511, file) == NULL) break;
    buf[511]='\0';

    if(sscanf(buf, "%d %d %d %d %d %d",
        var+0, var+1, var+2, var+3, var+4, var+5) != 6)
    {
        fprintf(stderr, "Couldn't read 6 items\n");
        continue;
    }

    printf("col 1=%d, col 4 = %d\n", var[0], var[3]);
}