df.c

// SPDX-License-Identifier: GPL-3.0-or-later

#include "config.h"
#define VERBOSE
#include "common.h"

#define PROC_MOUNTS "/proc/mounts"

static char linebuf[1024];

struct mount {
	char *dev;
	char *mountpoint;
	char *type;
	char *opts;
	char *dump;
	char *pass;
};

static int parse_mount(char *line, struct mount *mount)
{
	char *dev;
	char *mountpoint;
	char *type;
	char *opts;
	char *dump;
	char *pass;

	dev = line;

	/* Mount point should be after the dev */
	mountpoint = strchr(line, ' ');
	if (!mountpoint) {
		verbose("Didn't find mountpoint in line\n");
		return -EINVAL;
	}
	*mountpoint++ = '\0';

	/* type should be after the mount point */
	type = strchr(mountpoint, ' ');
	if (!type) {
		verbose("Didn't find type in line\n");
		return -EINVAL;
	}
	*type++ = '\0';

	/* options should be after the type */
	opts = strchr(type, ' ');
	if (!opts) {
		verbose("Didn't find opts in line\n");
		return -EINVAL;
	}
	*opts++ = '\0';

	/* dump should be after the options */
	dump = strchr(opts, ' ');
	if (!dump) {
		verbose("Didn't find dump in line\n");
		return -EINVAL;
	}
	*dump++ = '\0';

	/* pass should be after dump */
	pass = strchr(dump, ' ');
	if (!pass) {
		verbose("Didn't find pass in line\n");
		return -EINVAL;
	}
	*pass++ = '\0';

	mount->dev = dev;
	mount->mountpoint = mountpoint;
	mount->type = type;
	mount->opts = opts;
	mount->dump = dump;
	mount->pass = pass;

	return 0;
}

static int process_line(char *line)
{
	long long total = 0;
	long long avail = 0;
	long long used = 0;
	struct mount mount;
	struct statfs buf;
	int usepercent;
	int ret;

	ret = parse_mount(line, &mount);
	if (ret)
		return ret;

	ret = statfs(mount.mountpoint, &buf);
	if (ret) {
		verbose("stafs(%s, ..) failed: %d\n", mount.mountpoint, errno);
		return -1;
	}

	if (buf.f_bsize) {
		total = ((long long)buf.f_blocks * buf.f_bsize) / 1024;
		avail = ((long long)buf.f_bavail * buf.f_bsize) / 1024;
		used  = ((long long)(buf.f_blocks - buf.f_bfree) * buf.f_bsize) / 1024;
		usepercent = total ? (int)(used * 100 / total) : 0;
	}

	printf("%-20s %12lld %12lld %12lld %4d%% %s\n",
		mount.type, total, used, avail, usepercent, mount.mountpoint);

	return 0;
}

int main (int argc, char **argv, char **envp)
{
	unsigned int pos = 0;
	int __cleanup_fd fd;
	int ret;

	fd = open(PROC_MOUNTS, O_RDONLY);
	if (fd < 0) {
		verbose("Failed to open %s\n", PROC_MOUNTS);
		return 1;
	}

	printf("%-20s %12s %12s %12s %5s %s\n",
		"Filesystem", "1K-blocks", "Used", "Available", "Use%", "Mounted on");

	while (true) {
		ret = read(fd, &linebuf[pos], 1);
		if (ret == 0)
			break;

		if (ret != 1) {
			verbose("Failed to read from input\n");
			return 1;
		}

		if (linebuf[pos] == '\n') {
			linebuf[pos] = '\0';
			ret = process_line(linebuf);
			if (ret) {
				verbose("Failed to process input line\n");
				return 1;
			}

			pos = 0;
		}
		else
			pos++;
	}

	return 0;
}