creating/editing (text)files

[deute]

Hi guys,
I want a plugin to create a file (in the same directory) or if it allready exists to change it.
Think these are the functions i could use. But  I am not sure how to use them.
 int (*open_utf8)(const char* pathname, int flags);
 int (*open)(const char* pathname, int flags, ...);
 int (*close)(int fd);
 int (*creat)(const char *pathname, mode_t mode);
 int (*fdprintf)(int fd, const char *fmt, ...) ATTRIBUTE_PRINTF(2, 3);
 int (*read_line)(int fd, char* buffer, int buffer_size);

For example I don't know what flags I could pass to (*open). Or what is this , mode_t mode?
Maybe someone could explain at a little example to open a file and write something to it? Would be nice

[nls]

the file io stuff is (pretty close to) POSIX compliant so docs aplenty are available on the web. For example http://linux.die.net/man/2/open

The best documentation is the code so either look at the functions and see what they do or perhaps easier, look at other plugins and how they use them.