CODEWITHSUNDEEP
cunix
user32262
user32262

Reputation: 8850

Store output from Unix command in C code

int main()  {
    char buf[100];
    FILE *fp = popen("df -P /myLoc", "r");
    while (fgets(buf, 100, fp) != NULL) {
        printf( "%s", buf);
    }
    pclose(fp);

    return 0;
}

Output:

Filesystem             512-blocks  Used  Available Capacity Mounted on
/dev0/vol0             123456      3456   5464675     4%    /sys

I got the output of command in buf variable. But I need to get the value of Capacity (4 in this case) into an integer variable. I think cut or awk command can be used but not sure how to make it work exactly.

Any help is appreciated.

Upvotes: 0

Views: 626

Answers (2)

pmr
pmr

Reputation: 59811

If you want to use shell tools, you should write a shell-script.

If this really has to be in C you should use the system calls provided by POSIX instead of cobbling things together through popen. In you case that would be statvfs and the member f_favail of the statvfs struct.

#include <stdio.h>
#include <sys/types.h>
#include <sys/statvfs.h>

int main()
{
  struct statvfs buf;
  statvfs("/my/path", &buf);
  printf("Free: %lu", buf.f_favail);

  return 0;
}

Upvotes: 6

Nobilis
Nobilis

Reputation: 7448

Replace your df command with df -P /myLoc | awk '{print $5}' | tail -n 1 | cut -d'%' -f 1.

This will return 4 in your case. Then you can use atoi() to convert it to an int.

But as others have suggested using system calls should at least be more portable.

Upvotes: 2

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