What is stdin?

stdin stands for "standard input." It is a file descriptor that is used by programs to receive input data. By default, input is read from stdin, which is typically the keyboard or terminal where the program is executed.

In many programming languages, you can read from stdin using functions like input() in Python or std::io::stdin() in Rust. You can also redirect input from files or other processes using shell commands. For example:

$ cat input.txt | python3 prog.py

In this command, the contents of input.txt are piped into prog.py, allowing the program to read the data as if it were typed directly into the terminal.