MIPS Assembly File Writing - mips

Question

I am trying to write to a file in MIPS assembly and it seems that I cannot get it to work. The code is straightforward, but the $v0 register returns -1 no matter what I type. I have tried other people's code and still end up getting the same results.
The code:
filename: .asciiz "file.txt"
buffer: .asciiz "hello textual world"
.text
open_file:
li $v0, 13 # open file
la $a0, filename # file name
li $a1, 1 # write flag
li $a2, 0 # ignore mode
syscall
jal print
write_to_file:
move $a0, $v0 # descriptor
li $v0, 15 # write to file
la $a1, buffer # buffer
li $a2, 20 # max chars to write
syscall
jal print
close_file:
li $v0, 16 # close
# move $a0, $v0 # descriptor
syscall
jal print
li $v0, 10 # exit program
syscall
print:
move $a0, $v0
li $v0, 1
syscall # print v0
li $v0, 11
li $a0, '\n'
syscall # print '\n'
jr $ra
The output:
-1
-1
16
-- program is finished running --
A Screenshot of the Mars dir. Note: I know that the dir contains "FILES.txt" rather than the "file.txt" one. However, I am trying to create a new file.
EDIT:
After some time I ran the program and solved the issue. For some reason, the first syscall did not return -1 when I ran it today, but the problem was that in "jal print", $v0 changed its value, which means that the line that follows it, first line of write_to_file label, loads an incorrect descriptor to $a0. Another potential problem is that I put 20 characters to print instead of 19.
Long story short, I've saved the file descriptor in $s0 and put 19 characters to be written and now the program works.