Add file descriptor constants

src/console.asm

@@ -1,6 +1,9 @@
 extern	EOS
 extern	NL
 extern	NR_write
+extern	FD_stdin
+extern	FD_stdout
+extern	FS_stderr
 extern	strlen
 extern	itoa
 
@@ -64,7 +67,7 @@ print:
 	mov	rdx, rax
 	mov	rax, NR_write
 	mov	rsi, rdi
-	mov	rdi, 1
+	mov	rdi, FD_stdout
 	syscall
 	ret
 ;----- puts (char* string) -----;
@@ -74,7 +77,7 @@ puts:
 	call	print
 	mov	rdi, r10
 	mov	rax, NR_write
-	mov	rdi, 1
+	mov	rdi, FD_stdout
 	mov	rsi, bNL
 	mov	rdx, 1
 	syscall
@@ -244,7 +247,7 @@ printf:
 	push	r8
 	push	r9
 	mov	rax, NR_write
-	mov	rdi, 1
+	mov	rdi, FD_stdout
 	lea	rsi, [rel printfBuff]
 	mov	rdx, r14
 	mov	byte [r11], 0x0
@@ -267,7 +270,7 @@ printf:
 	.finish:
 	mov	byte [r11], 0x0
 	mov	rax, NR_write
-	mov	rdi, 1
+	mov	rdi, FD_stdout
 	lea	rsi, [rel printfBuff]
 	mov	rdx, r14
 	add	r13, r14

src/constants.asm

@@ -4,6 +4,10 @@ section .rodata
 	global	NR_open
 	global	NR_close
 	global	NR_exit
+
+	global	FD_stdin
+	global	FD_stdout
+	global	FD_stderr
 	
 	global	EOS
 	global	NL
@@ -15,6 +19,11 @@ section .rodata
 	NR_close	equ	3
 	NR_exit		equ	60
 
+	;file descriptors
+	FD_stdin	equ	0
+	FD_stdout	equ	1
+	FD_stderr	equ	2
+
 	;ascii
 	EOS		equ	0x0
 	NL		equ	0xA

src/file.asm

@@ -1,3 +1,4 @@
+extern	FD_stderr
 extern	NR_read
 extern	NR_write
 extern	NR_open
@@ -80,8 +81,8 @@ fclose:
 ; writes a string to opened file
 ; return value: amount of written characters on success, below 0 otherwise (neg errno)
 fwrite:
-	cmp	rdi, 3
-	jl	.ebadf
+	cmp	rdi, FD_stderr
+	jle	.ebadf
 
 	mov	r9, rdi
 	mov	rdi, rsi