Question

I know you have to use …

php lots_of_errors.php > temp.txt 2>&1

…if you want to redirect the error logs into a temp.txt

• 1 = standard output (where programs print normal output)
• 2 = standard error (where programs print errors)

You use &1 to indicate that it’s a file descriptor and not a file but why don’t you use & sign in front of 2 like &2>&1 then?

Answer 1

Because the & symbol is how the shell knows you are redirecting to a file descriptor instead of a file. That is, the lefthand-side (LHS) of the > operator is always a file descriptor, but the RHS is generally a filename. So this:

2>1

Would redirect file descriptor 2 to a filenamed “1”. The amperand is how the shell knows you mean “file descriptor 1”:

2>&1