implement dup syscall

libc/CMakeLists.txt

@@ -5,6 +5,7 @@
 # Add the library.
 add_library(
     libc
+    ${CMAKE_SOURCE_DIR}/libc/src/unistd/dup.c
     ${CMAKE_SOURCE_DIR}/libc/src/stdio.c
     ${CMAKE_SOURCE_DIR}/libc/src/ctype.c
     ${CMAKE_SOURCE_DIR}/libc/src/string.c

libc/inc/sys/unistd.h

@@ -253,6 +253,12 @@ int fchdir(int fd);
 ///         appropriately.
 ssize_t getdents(int fd, dirent_t *dirp, unsigned int count);
 
+/// @brief Return a new file descriptor
+/// @param fd The fd pointing to the opened file.
+/// @return On success, a new file descriptor is returned.
+///         On error, -1 is returned, and errno is set appropriately.
+int dup(int fd);
+
 /// @brief Send signal to calling thread after desired seconds.
 /// @param seconds the amount of seconds.
 /// @return If there is a previous alarm() request with time remaining, alarm()

libc/src/unistd/dup.c

@@ -0,0 +1,10 @@
+/// @file dup.c
+/// @brief
+/// @copyright (c) 2024 This file is distributed under the MIT License.
+/// See LICENSE.md for details.
+
+#include "sys/unistd.h"
+#include "system/syscall_types.h"
+#include "sys/errno.h"
+
+_syscall1(int, dup, int, fd)