Описание тега stderr
The standard error output stream (stderr) is typically used by a program to output error messages or diagnostics.
The standard error stream, stderr, is a stream typically used by a program to output error or diagnostic messages. It is one of the three standard streams used by a UNIX-like program, along with stdin and stdout.
Like stdout, stderr is outputted to the text terminal unless redirected.
The file descriptor for standard output is 2 (two); the POSIX definition is STDERR_FILENO.