Added df

2 files changed, 122 insertions, 2 deletions

diff --git a/README.md b/README.md
index 308cfe0..003dc25 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,7 @@
 # coreutils
 
 Rewrite of some core utilities for educational purposes.
+I try to follow the POSIX version of those commands for simplicity sake, e.g `man 1p ls`.
 
 | Name       | Description                                                      |
 |------------|----------------------------------------------------------------- |
@@ -12,20 +13,23 @@ Rewrite of some core utilities for educational purposes.
 | `shuf`     | generate random permutations                                     |
 | `echo`     | display a line of text                                           |
 | `yes`      | output a string repeatedly until killed                          |
+| `df`       | report free disk space                                           |
+
 
 ## Pending
 
-| Name       | Description |
+| Name       | Description                                                      |
 |------------|----------------------------------------------------------------- |
 | `cut`      | remove sections from each line of files                          |
 | `uniq`     | report or omit repeated lines                                    |
 | `tr`       | translate or delete characters                                   |
 | `chown`    | change file owner and group                                      |
 | `xargs`    | construct argument lists and invoke utility                      |
+| `ps`       | report process status                                            |
 
 ## TODO
 
-| Name       | Description |
+| Name       | Description                                                     |
 |------------|-----------------------------------------------------------------|
 | `cp`       | |
 | `chmod`    | |
diff --git a/src/df.c b/src/df.c
new file mode 100644
index 0000000..9c0b5eb
--- /dev/null
+++ b/src/df.c
@@ -0,0 +1,116 @@
+#define _POSIX_C_SOURCE 200809L
+#define _XOPEN_SOURCE 500
+
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <sys/statvfs.h>
+#include <math.h>
+#include <limits.h>
+
+static unsigned long g_output_block_size = 512;
+
+typedef struct
+{
+	char name[PATH_MAX + 1];
+	char mount[PATH_MAX + 1];
+} t_fs_info;
+
+static t_fs_info g_fs_info_dummy = { .name = "", .mount = "" };
+
+static t_fs_info *g_fs_infos      = NULL;
+static size_t     g_fs_infos_size = 0;
+
+void put_file_fs_info(char *file_relpath, bool allow_empty)
+{
+	char file_path[PATH_MAX + 1] = {'\0'};
+	realpath(file_relpath, file_path);
+
+	struct statvfs statvfsbuf;
+	if (statvfs(file_path, &statvfsbuf) == -1)
+		exit(1);
+
+	long block_size     = statvfsbuf.f_bsize;
+	unsigned long total = statvfsbuf.f_blocks * statvfsbuf.f_frsize / g_output_block_size;
+	long used           = total - statvfsbuf.f_bfree  * block_size / g_output_block_size;
+	long available      = statvfsbuf.f_bavail * block_size / g_output_block_size;
+
+	bool empty_fs = used + available == 0;
+	if (empty_fs && !allow_empty)
+		return;
+
+	t_fs_info *fs_info = &g_fs_info_dummy;
+	for (size_t i = 0; i < g_fs_infos_size; i++)
+	{
+		char *mount = g_fs_infos[i].mount;
+		size_t mount_len = strlen(mount);
+		if (strncmp(file_path, mount, mount_len) == 0 && mount_len > strlen(fs_info->mount))
+			fs_info = &g_fs_infos[i];
+	}
+
+	printf("%-15s", fs_info->name);
+	printf("%11ld",  total);
+	printf("%9ld",   used);
+	printf("%10ld",  available);
+	if (!empty_fs)
+		printf("%8.0f%%", ceil(((double)used / (double)(used + available)) * 100));
+	else
+		printf("%9c", '-');
+	printf(" %s", fs_info->mount);
+	fputc('\n', stdout);
+}
+
+int main(int argc, char **argv)
+{
+	int option;
+
+	while ((option = getopt(argc, argv, "kPt")) != -1)
+	{
+		switch (option)
+		{
+			case 'k':
+				g_output_block_size = 1024;
+				break;
+			case 'P':
+			case 't':
+				break;
+		}
+	}
+
+	FILE *mounts_file = fopen("/etc/mtab", "r");
+	if (mounts_file == NULL)
+		exit(1);
+	while (!feof(mounts_file))
+	{
+		g_fs_infos_size++;
+		g_fs_infos = realloc(g_fs_infos, sizeof(t_fs_info) * g_fs_infos_size);
+		if (g_fs_infos == NULL)
+		{
+			fclose(mounts_file);
+			exit(1);
+		}
+		t_fs_info *last = &g_fs_infos[g_fs_infos_size - 1];
+		fscanf(mounts_file, "%s %s", &last->name, &last->mount);
+		int c;
+		do
+			c = fgetc(mounts_file);
+		while (c != '\n' && c != EOF);
+	}
+	fclose(mounts_file);
+	g_fs_infos_size--;
+
+	printf("Filesystem     %4lu-blocks     Used Available Capacity Mounted on\n", g_output_block_size);
+
+	if (optind == argc)
+	{
+		for (size_t i = 0; i < g_fs_infos_size; i++)
+			put_file_fs_info(g_fs_infos[i].mount, false);
+		return 0;
+	}
+	for (; optind < argc; optind++)
+		put_file_fs_info(argv[optind], true);
+	free(g_fs_infos);
+	return 0;
+}