Files Library

The unistd.h library contains methods for working with files:

#include<unistd.h>
int open(const char *name, int flags);
int open(const char* name, int flags, mode_t mode);
int close();

The flag parameter (flag) is a bitmask defining the following:

flag	Information
O_APPEND	The file will be opened in append mode.
O_ASYNC	SIGIO is generated when it can be read or written.
O_CREAT	If the file does not exist, it creates it.
O_DIRECT	Opens the file for direct input/output.
O_DIRECTORY	If the name is not a directory, it gives an error
O_EXCL	If O_CREAT and the file exists, it gives an error.
O_LARGEFILE	Opens a file larger than 2 GB
O_NOCTTY	This flag is not used
O_NOFOLLOW	If name is a symbolic link, it gives an error
O_NONBLOCK	If possible, opens the file in non-blocking mode.
O_SYNC	The file will be opened for synchronous Input/Output
O_TRUNC	If the file exists, it is truncated to zero length

In case the O_CREAT flag is set, the mode is a bitmask as follows:

S_IRWXU	S_IXUSR	S_IWGRP	S_IROTH
S_IRUSR	S_IRWXG	S_IXGRP	S_IWOTH
S_IWUSR	S_IRGRP	S_IRWXO	S_IXOTH