Posix System Commands

bytes.

In modern POSIX compliant operating systems, a program that needs to access data from a file stored in a file system uses this system call.

descriptor

open

• The file descriptor of the file.
• The buffer where the read data is to be stored
• The number of bytes to be read from the file.

An abstract indicator (handle) used to access a file or other input/output resource, such as a pipe or network socket.

For most file systems, a program initializes access to a file in a file system using this system call. This allocates resources associated to the file (the file descriptor), and returns a handle that the process will use to refer to that file. In some cases this  system call is performed by the first access.

• The pathname to the file
• The kind of access requested on the file (read, write, append etc.)
• The initial file permission is requested using the third argument called mode. This argument is relevant only when a new file is being created.

The name of the file to open. It includes the file path defining where, in which file system, the file is found (or should be created).

This argument formed by OR'ing together optional parameters and (from <fcntl.h>) one of the following: O_RDONLY, O_RDWR and O_WRONLY