How does select system call work?

The select system call monitors three sets of independent file descriptors. If none of the descriptors in the three sets become ready, select would return after the interval pointed by timeout. If timeout is NULL, select would block till at least one descriptor in the three sets is ready.

What is select in networking?

select is a system call and application programming interface (API) in Unix-like and POSIX-compliant operating systems for examining the status of file descriptors of open input/output channels. The select system call is similar to the poll facility introduced in UNIX System V and later operating systems.

How does select socket work?

2 Answers. select chooses which fds to watch based on the fd sets you pass in ( readfds , writefds , exceptfds ). The sets are typically implemented as bit vectors, so select will scan over the vector to see what fds are selected.

Why do we need select system call?

The select() system call enables a system to keep track of several file descriptors. So, the select system call waits for one of the descriptors or a whole to turn out to be “ready” for a particular type of I/O activity (e.g., input possible).

What is select select?

The select. select() method provides the I/O multiplexing as provided by the Unix function call select(). select() is a system call. It tells the kernel to notify when any of the descriptors in the sets are ready for read/write/exception conditions.

What does select function do in C?

A better solution is to use the select function. This blocks the program until input or output is ready on a specified set of file descriptors, or until a timer expires, whichever comes first. This facility is declared in the header file sys/types.

Is select blocking call?

By using the select() call, you do not issue a blocking call until you know that the call cannot block. The select() call can itself be blocking, nonblocking, or, for the macro API, asynchronous.

How does select work in Python?

Python’s select() function is a direct interface to the underlying operating system implementation. It monitors sockets, open files, and pipes (anything with a fileno() method that returns a valid file descriptor) until they become readable or writable, or a communication error occurs.