OpenFile parameters

[No_Name]

OpenFile function takes three parameters and I understand what first two are used for, but I struggle to understand what the third one is used for
example of using OpenFile function:

file, err = os.OpenFile("test.txt", os.O_APPEND, 0666)

The first parameter is the file name, the second parameter is what we can do with the file (in this case - append), but what does the third parameter determine?

[Sibert]

@No_Name

but what does the third parameter determine?

Permissions (read/write/execute)

ioutil package - io/ioutil - Go Packages

[No_Name]

Thanks you, could you tell me where can I read about all the existing permission modes,please?

[Sibert]

@No_Name

where can I read about all the existing permission

http://permissions-calculator.org is one link. I have never used the first position. 0777 is read/write/execute for all