Ferreteria/v0.6/clade/Sys/FileSys/Mode/fopen modes

Modes in fopen()

About

(The following is Take 2b of trying to figure this out; previous attempts are here. I changed "E" (exists) to "F" (found).)

• R = readable?
• W = writable?
• C = create file if not found?
• F = what to do if existing file found
  • ! = fail (return with error)
  • 0 = erase (truncate to zero length)
  • > = set pointer to end of file

Value-states

• - = must be OFF/disabled
• + = must be ON/enabled

mode | R | W | C | F | documentation says...
-----+---+---+---+---+---+----------------------
 r   | 1 | 0 | 0 |   | ...reading only; start of file.
 r+  | 1 | 1 | 0 |   | ...reading and writing; place the file pointer at the beginning of the file.
 w   | 0 | 1 | 1 | 0 | ...writing only; start of file; truncate to zero length. If the file does not exist, attempt to create it.
 w+  | 1 | 1 | 1 | 0 | ...reading and writing; otherwise it has the same behavior as 'w'.
 a   | 0 | 1 | 1 | > | ...writing only; file pointer at end of file. Create if not found. fseek() has no effect, writes are always appended.
 a+  | 1 | 1 | 1 | > | ...reading and writing; file pointer at end of file. Create if not found. fseek() only affects reading, writes appended.
 x   | 0 | 1 | 1 | ! | ...writing only; file pointer at start of file. FAIL if found; create if not found.
 x+  | 1 | 1 | 1 | ! | ...reading and writing; otherwise it has the same behavior as 'x'.
 c   | 0 | 1 | 1 |   | ...writing only. Create if not found. No action if found. File pointer at start of file.
 c+  | 1 | 1 | 1 |   | ...Open the file for reading and writing; otherwise it has the same behavior as 'c'.

The mode-request will now be a string consisting of repeated [R|W|C|E]<value> (case-insensitive), with optional spaces for readability.

Examples

• r+ c+ = readable file, create if needed
• r+ w+ c+ f- = read-write file, create if needed, clear any existing contents
• r- w+ = file must be write-only, don't care about other features