File Control (fcntl)

Function Prototype

int fcntl(int filedes, int cmd, .../* int arg*/);

We put the command (flag) we want to execute in cmd section, if the command require extra argument then we put them into arg section

Change the properties of open files

F_DUPFD - similar to dup, but we can specify the lowest file descriptor number we want in arg

管理 open file desc. table 的 flag

管理 open file table 的 flag

These flags work with flags belong to open file table

O_APPEND- same as that in open
O_NONBLOCK - turn open file object to non-blocking
O_SYNC - same as that in open
O_ASYNC - enables asynchronous I/O notification, the system will send a signal when data become available for read/write
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