diff --git a/lib/libc/include/fcntl.h b/lib/libc/include/fcntl.h
index d590e14..4500a26 100644
--- a/lib/libc/include/fcntl.h
+++ b/lib/libc/include/fcntl.h
@@ -1,6 +1,8 @@
 #ifndef FCNTL_H_
 #define FCNTL_H_
 
+#include <sys/types.h>
+
 #define O_RDONLY   0x0000 /* open for reading only */
 #define O_WRONLY   0x0001 /* open for writing only */
 #define O_RDWR     0x0002 /* open for reading and writing */
@@ -50,4 +52,47 @@
 #define AT_SYMLINK_NOFOLLOW_ANY                                                \
 	0x0800 /* Path should not contain any symlinks */
 
+#define S_IRWXU  00700
+#define S_IRUSR  00400
+#define S_IWUSR  00200
+#define S_IXUSR  00100
+#define S_IRWXG  00070
+#define S_IRGRP  00040
+#define S_IWGRP  00020
+#define S_IXGRP  00010
+#define S_IRWXO  00007
+#define S_IROTH  00004
+#define S_IWOTH  00002
+#define S_IXOTH  00001
+#define S_ISUID  0004000
+#define S_ISGID  0002000
+#define S_ISVTX  0001000
+
+#define R_OK     4
+#define W_OK     2
+#define X_OK     1
+#define F_OK     0
+
+#define F_RDLCK  0
+#define F_WRLCK  1
+#define F_SETLKW 7
+
+struct flock {
+	short l_type;
+	short l_whence;
+	off_t l_start;
+	off_t l_len;
+	pid_t l_pid;
+};
+
+struct flock64 {
+	short l_type;
+	short l_whence;
+	off_t l_start;
+	off_t l_len;
+	pid_t l_pid;
+};
+
+extern int fcntl(int fd, int op, ...);
+
 #endif
diff --git a/lib/libc/include/stdio.h b/lib/libc/include/stdio.h
index ff34c51..f1a33ae 100644
--- a/lib/libc/include/stdio.h
+++ b/lib/libc/include/stdio.h
@@ -26,6 +26,7 @@ extern int printf(const char *format, ...);
 extern int vprintf(const char *format, va_list arg);
 extern int fprintf(FILE *stream, const char *format, ...);
 extern int vfprintf(FILE *stream, const char *format, va_list arg);
+extern int sprintf(char *buffer, const char *format, ...);
 extern int snprintf(char *buffer, size_t count, const char *format, ...);
 extern int vsnprintf(
 	char *buffer,
@@ -34,6 +35,8 @@ extern int vsnprintf(
 	va_list va);
 
 extern FILE *fopen(const char *path, const char *mode);
+extern FILE *fdopen(int fildes, const char *mode);
+
 extern int fclose(FILE *stream);
 
 extern int feof(FILE *stream);
@@ -60,6 +63,7 @@ extern int fputs(const char *restrict str, FILE *restrict stream);
 
 extern long ftell(FILE *stream);
 extern int fseek(FILE *stream, long offset, int origin);
+extern int fflush(FILE *stream);
 
 extern int sscanf(
 	const char *restrict buffer,
diff --git a/lib/libc/include/stdlib.h b/lib/libc/include/stdlib.h
index bef2fae..fc53007 100644
--- a/lib/libc/include/stdlib.h
+++ b/lib/libc/include/stdlib.h
@@ -8,6 +8,11 @@ extern void abort(void);
 extern void exit(int result);
 extern int atexit(void (*func)(void));
 
+extern int abs(int v);
+extern int atoi(const char *str);
+
+extern char *getenv(const char *name);
+
 extern void *malloc(size_t count);
 extern void *calloc(size_t count, size_t size);
 extern void *realloc(void *p, size_t count);
diff --git a/lib/libc/include/string.h b/lib/libc/include/string.h
index 4951bc2..50189c4 100644
--- a/lib/libc/include/string.h
+++ b/lib/libc/include/string.h
@@ -10,6 +10,7 @@ extern size_t strlen(const char *s);
 
 extern size_t strcspn(const char *dest, const char *src);
 
+extern char *strcat(char *dest, const char *src);
 extern char *strchr(const char *str, int c);
 extern char *strrchr(const char *str, int ch);
 
diff --git a/lib/libc/include/sys/stat.h b/lib/libc/include/sys/stat.h
new file mode 100644
index 0000000..7c6e73c
--- /dev/null
+++ b/lib/libc/include/sys/stat.h
@@ -0,0 +1,8 @@
+#ifndef SYS_STAT_H_
+#define SYS_STAT_H_
+
+#include <sys/types.h>
+
+extern int mkdir(const char *path, mode_t mode);
+
+#endif
diff --git a/lib/libc/include/sys/types.h b/lib/libc/include/sys/types.h
index 72577d9..6630974 100644
--- a/lib/libc/include/sys/types.h
+++ b/lib/libc/include/sys/types.h
@@ -8,7 +8,7 @@
 #define SEEK_END 2
 
 typedef size_t ino_t;
-typedef long pid_t;
+typedef int pid_t;
 typedef long mode_t;
 
 struct dentry {
diff --git a/lib/libc/include/unistd.h b/lib/libc/include/unistd.h
index 269b71c..8e69a41 100644
--- a/lib/libc/include/unistd.h
+++ b/lib/libc/include/unistd.h
@@ -4,12 +4,14 @@
 #include <stddef.h>
 #include <sys/types.h>
 
-extern int open(const char *path, int flags);
+extern int open(const char *path, int flags, ...);
 extern int close(int fd);
 
 extern int read(int fd, void *buf, size_t count);
 extern int write(int fd, const void *buf, size_t count);
 
+extern int access(const char *path, int mode);
+
 extern off_t lseek(int fd, off_t offset, int whence);
 
 extern long getdents(int fd, struct dentry *dirp, unsigned int count);
@@ -20,7 +22,11 @@ extern int execl(const char *path, const char *arg, ...);
 extern int execlp(const char *file, const char *arg, ...);
 extern int execle(const char *path, const char *arg, ...);
 extern int execv(const char *path, char *const argv[]);
+extern int execve(const char *path, char *const argv[], char *const envp[]);
 extern int execvp(const char *file, char *const argv[]);
 extern int execvpe(const char *file, char *const argv[], char *const envp[]);
 
+extern pid_t getpid(void);
+extern pid_t getppid(void);
+
 #endif