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.

Redirecting Input
    Redirection  of  input  causes  the  file  whose name results from the expansion of word to be opened for
    reading on file descriptor n, or the standard input (file descriptor 0) if n is not specified.

    The general format for redirecting input is:

           [n]<word

construct argument lists and invoke utility

-I  replstr
       Insert mode: utility is executed for each line from standard input, taking the entire  line  as  a
       single  argument,  inserting  it  in  arguments  for each occurrence of replstr. A maximum of five
       arguments in arguments can each contain one or more instances of  replstr.  Any  <blank>s  at  the
       beginning  of each line shall be ignored. Constructed arguments cannot grow larger than 255 bytes.
       Option -x shall be forced on.