Add a simple /bin/df which gathers its info from /proc/df.

Userland/df.cpp

@@ -0,0 +1,55 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <AK/AKString.h>
+#include <AK/Vector.h>
+
+struct FileSystem {
+    String fs;
+    size_t total_block_count { 0 };
+    size_t free_block_count { 0 };
+    size_t total_inode_count { 0 };
+    size_t free_inode_count { 0 };
+    String mount_point;
+};
+
+int main(int, char**)
+{
+    FILE* fp = fopen("/proc/df", "r");
+    if (!fp) {
+        perror("failed to open /proc/df");
+        return 1;
+    }
+    printf("Filesystem    Blocks        Used    Available   Mount point\n");
+    for (;;) {
+        char buf[4096];
+        char* ptr = fgets(buf, sizeof(buf), fp);
+        if (!ptr)
+            break;
+        auto parts = String(buf, Chomp).split(',');
+        if (parts.size() < 6)
+            break;
+        bool ok;
+        String fs = parts[0];
+        unsigned total_block_count = parts[1].to_uint(ok);
+        ASSERT(ok);
+        unsigned free_block_count = parts[2].to_uint(ok);
+        ASSERT(ok);
+        unsigned total_inode_count = parts[3].to_uint(ok);
+        ASSERT(ok);
+        unsigned free_inode_count = parts[4].to_uint(ok);
+        ASSERT(ok);
+        String mount_point = parts[5];
+
+        printf("% 10s", fs.characters());
+        printf("%10u  ", total_block_count);
+        printf("%10u   ", total_block_count - free_block_count);
+        printf("%10u   ", free_block_count);
+        printf("%s", mount_point.characters());
+        printf("\n");
+    }
+    int rc = fclose(fp);
+    ASSERT(rc == 0);
+    return 0;
+}