It can be seen that stdin, stdout, stderr are all objects of file properties in Python, They are automatically associated with standard inputs, outputs, and errors in the Shell environment when Python is started. The I/O redirection of the Python program in the shell is exactly the same as the redirection of the DOS command,. stdout Definition. Also known as standard output, stdout is the destination of all but the error-related output of a command. An example of stdout is the return value from a function call. Description: ------------ When using the PHP CLI executable, the script can be named on the command line, or fed to PHP through standard input. If using standard input, the file constants STDIN, STDOUT, and STDERR are undefined. I can understand not defining STDIN, since the script is read from there, but why are STDOUT and STDERR not defined?. "/>Where is stdout defined