Why does fopen fail the first time, but work the second time?

Question

I am using Matlab to create a new file by calling

fid = fopen(filename,'w')

since filename doesn't exist, it should create a new file and give me a valid file descriptor. Instead it returns -1. If I run the code again however, I get fid = 3.

This is being run on ubuntu but it apparently works fine on windows and I can't figure out why.

-Mike

Answer 1

not sure if this helps, but note that if the folder doesn't exist, fopen with 'w' can't create the file and so returns -1.