dfが何を使って出力しているのか調べたコード

fs_darwin.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <inttypes.h>
#include <errno.h>
#include <sys/mount.h>

// /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/stdint.h 

char *argv0;

void fstats(void);
void fstat(char *);
void printstat(struct statfs *);
uintmax_t bused(struct statfs *);
uintmax_t bsize(struct statfs *, uintmax_t);

int
main(int argc, char **argv)
{
	int i;

	argv0 = argv[0];
	if(argc == 1)
		fstats();
	else
		for(i = 1; i < argc; i++)
			fstat(argv[i]);
	return 0;
}

void
fstats(void)
{
	struct statfs *f, *p, *e;
	int n;

	n = getmntinfo(&f, MNT_NOWAIT);
	if(n < 0){
		fprintf(stderr, "%s: getmntinfo: %s\n", argv0, strerror(errno));
		return;
	}
	e = f+n;
	for(p = f; p < e; p++){
		if(p > f)
			printf("\n");
		printstat(p);
	}
	free(f);
}

void
fstat(char *path)
{
	struct statfs fs;

	if(statfs(path, &fs) < 0){
		fprintf(stderr, "%s: statfs: %s\n", argv0, strerror(errno));
		exit(1);
	}
	printstat(&fs);
}

void
printstat(struct statfs *f)
{
	printf("mounted on %s\n", f->f_mntonname);
	printf("fstype %s\n", f->f_fstypename);
	printf("block size %u\n", f->f_iosize);
	printf("fragment size %u\n", f->f_bsize);
	printf("fragments in a block %u\n", f->f_iosize/f->f_bsize);

	printf("used blocks %" PRIuMAX "\n", bsize(f, bused(f)));
	printf("avail blocks %" PRIuMAX "\n", bsize(f, f->f_bavail));
	printf("total blocks %" PRIuMAX "\n", bsize(f, f->f_blocks));
	printf("used inodes %" PRIu64 "\n", f->f_files - f->f_ffree);
	printf("free inodes %" PRIu64 "\n", f->f_ffree);
	printf("flags");
	if(f->f_flags&MNT_RDONLY)
		printf(" readonly");
	printf("\n");
}

uintmax_t
bused(struct statfs *f)
{
	return f->f_blocks - f->f_bfree;
}

uintmax_t
bsize(struct statfs *f, uintmax_t n)
{
	return n * f->f_bsize / 512;
}

fs_linux.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <inttypes.h>
#include <errno.h>
#include <mntent.h>
#include <sys/statvfs.h>

char *argv0;

void fstats(void);
void fstat(char *);
uintmax_t bused(struct statvfs *);
uintmax_t bsize(struct statvfs *, uintmax_t);

int
main(int argc, char **argv)
{
	int i;

	argv0 = argv[0];
	if(argc == 1)
		fstats();
	else
		for(i = 1; i < argc; i++)
			fstat(argv[i]);
	return 0;
}

void
fstats(void)
{
	FILE *r;
	struct mntent *p;

	r = setmntent("/etc/mtab", "r");
	while(p = getmntent(r))
		fstat(p->mnt_dir);
	endmntent(r);
}

void
fstat(char *path)
{
	struct statvfs fs;

	if(statvfs(path, &fs) < 0){
		fprintf(stderr, "%s: statvfs: %s\n", argv0, strerror(errno));
		exit(1);
	}
	printf("path %s\n", path);
	printf("block size %lu\n", fs.f_bsize);
	printf("fragment size %lu\n", fs.f_frsize);
	printf("fragments in a block %lu\n", fs.f_bsize/fs.f_frsize);

	printf("used blocks %" PRIuMAX "\n", bsize(&fs, bused(&fs)));
	printf("avail blocks %" PRIuMAX "\n", bsize(&fs, fs.f_bavail));
	printf("total blocks %" PRIuMAX "\n", bsize(&fs, fs.f_blocks));
	printf("used inodes %u\n", fs.f_files - fs.f_ffree);
	printf("free inodes %u\n", fs.f_ffree);
	printf("flags");
	if(fs.f_flag&ST_RDONLY)
		printf(" readonly");
	printf("\n");
	printf("namelen %lu\n", fs.f_namemax);
	printf("\n");
}

uintmax_t
bused(struct statvfs *f)
{
	return f->f_blocks - f->f_bfree;
}

uintmax_t
bsize(struct statvfs *f, uintmax_t n)
{
	return n * f->f_frsize / 1024;
}