an example using blkid API in C lang

blkid_example.c

// compile hint: gcc xxx.c -lblkid
#include <unistd.h>
#include <stdio.h>
#include <stdbool.h>
#include <errno.h>
#include <blkid/blkid.h>

int list_ext4_partitions(void)
{
    int res;
    blkid_cache cache;
    res = blkid_get_cache(&cache, NULL);
    if (res != 0)
        perror("cannot get cache");
    blkid_dev_iterate it;
    blkid_dev dev;
    const char *name;
    const char *tag_value = "ext4";

    it = blkid_dev_iterate_begin(cache);
    res = 0;

    while (true)
    {
        res = blkid_dev_next(it, &dev);
        if (res != 0)
            break;
        name = blkid_dev_devname(dev);
        res = blkid_dev_has_tag(dev, "TYPE", tag_value);
        if (res == 0)
            continue;
        printf("%s  %s %d\n", name, tag_value, res);
    }

    printf("\n");

    return 0;
}

int get_size_sda1(void)
{
    blkid_probe pr;
    const char *ptname;
    const char *devname = "/dev/sda1";
    pr = blkid_new_probe_from_filename(devname);
    if (!pr)
        printf("%s: failed to open device", devname);

    int res = blkid_probe_enable_partitions(pr, 1);
    blkid_probe_set_partitions_flags(pr, BLKID_PARTS_ENTRY_DETAILS);
    printf("%d\n", res);
    res = blkid_do_fullprobe(pr);
    printf("%d\n", res);
    res =  blkid_probe_lookup_value(pr, "PART_ENTRY_SIZE", &ptname, NULL);
    printf("/dev/sda1 size:  %s\n", ptname);

    blkid_free_probe(pr);
}

int main()
{
    get_size_sda1();
    list_ext4_partitions();
    return 0;
}