REDIRECTION Before a command is executed, its input and output may be redirected using a special notation interpreted by the shell. Redirection may also be used to open and close files for the current shell execution environment. The following redirection operators may precede or appear anywhere within a simple command or may follow a command. Redirections are processed in the order they appear, from left to right.

       In the following descriptions, if the file descriptor number is
       omitted, and the first character of the redirection operator is <, the
       redirection refers to the standard input (file descriptor 0).  If the
       first character of the redirection operator is >, the redirection
       refers to the standard output (file descriptor 1).

       The word following the redirection operator in the following
       descriptions, unless otherwise noted, is subjected to brace expansion,
       tilde expansion, parameter expansion, command substitution, arithmetic
       expansion, quote removal, pathname expansion, and word splitting.  If
       it expands to more than one word, bash reports an error.

       Note that the order of redirections is significant.  For example, the
       command

              ls > dirlist 2>&1

       directs both standard output and standard error to the file dirlist,
       while the command

              ls 2>&1 > dirlist

       directs only the standard output to file dirlist, because the standard
       error was duplicated as standard output before the standard output was
       redirected to dirlist.