Linux application Development-i/o operation
linux-i/o
1 Kernel Method->VFS virtual file system->lib System API, System-related non-standard api-> standard C Api->app
2 Bus has many specifications, different specifications of the bus is not the same, the bus is used to transmit data, provide transmission and addressing methods, such as PCI is the bus specifications,
3 Hardware---driver---Bus (cable transfer data)--Virtual file system (with multiple file systems) (front of kernel space)--file--and program (open, Close, read) (followed by user space, mainly called API)
4 umask 0 0 2 2
Gid/uid own user group other user group
system default Umask = 0022
5 The open file should have a 4-digit permission column, such as 0666
6 The actual permissions for the created file are 0666-umask = 0444 =--wx-wx-wx
7 Get the length of the file int file_num = Lseek (FD, 0, seek_end);
8 Adding a new system call
9 Procedure for system calls
Linux Application Development-I/O operation
