public void checkWritable() {
		if (!OpenFlag.isWrite(flags)) {
			throw new EmuIOException("File not opened for writing");
		}
	}
Check if the file is writable, throwing {@link EmuIOException} if not
Ghidra/Features/SystemEmulation/src/main/java/ghidra/pcode/emu/unix/DefaultEmuUnixFileHandle.java