What is a file descriptor.
A file descriptor is a simple positive integer that identifies each file and socket that is opened by the process.
The first three file descriptors (0,1,2) correspond to standard input (stdin), standard output (stdout), and standard error (STDERR) respectively.
difference between "2>&1 > File" and "> File 2>&1".
1.php test.php 2>&1 > file: Error output to terminal, standard output redirected to file.
2.php test.php > File 2>&1: Standard output is redirected to file files, and the error output is redirected to the same as standard output, so errors are also exported to file files.
<?php
$fp = fopen ("Php://stderr", "w");
Fwrite ($fp, "stderr\n");
Fclose ($FP);
$fp = fopen ("Php://stdout", "w");
Fwrite ($fp, "stdout\n");
Fclose ($FP);
PHP test.php 2>&1 >/dev/null
/Result: stderr//php test.php
>/dev/null 2>&1//
result is no output C10/>?>
