shell read

 1）    cat /sites/linuxpig.com.txt |while read LINE
     do
         echo $LINE
     done
     

2）重定向的方式：

  2.1 利用重定向符<

     while read LINE
     do
         echo $LINE
     done < /sites/linuxpig.com.txt

  2.2 利用文件描述符（0~9）和重定向符 <

     exec 3<&0
     exec 0      while read LINE
     do
         echo $LINE
     done
     exec 0<&3

read [-ers] [-u fd] [-t timeout] [-a aname] [-p prompt] [-n nchars] [-d delim] [name ...]
              One  line  is read from the standard input, or from the file descriptor fd supplied as an argument
              to the -u option, and the first word is assigned to the first name, the second word to the  second
              name,  and  so on, with leftover words and their intervening separators assigned to the last name.
              If there are fewer words read from the input stream than names, the remaining names  are  assigned
              empty values.  The characters in IFS are used to split the line into words.  The backslash charac-
              ter (\) may be used to remove any special meaning for the next character read and for line contin-
              uation.  Options, if supplied, have the following meanings:
              -a aname
                     The  words  are  assigned to sequential indices of the array variable aname, starting at 0.
                     aname is unset before any new values are assigned.  Other name arguments are ignored.
              -d delim
                     The first character of delim is used to terminate the input line, rather than newline.
              -e     If the standard input is coming from a terminal, readline (see READLINE above) is  used  to
                     obtain the line.
              -n nchars
                     read  returns  after  reading  nchars characters rather than waiting for a complete line of
                     input.
              -p prompt
                     Display prompt on standard error, without a trailing newline, before attempting to read any
                     input.  The prompt is displayed only if input is coming from a terminal.
              -r     Backslash  does  not act as an escape character.  The backslash is considered to be part of
                     the line.  In particular, a backslash-newline pair may not be used as a line  continuation.
              -s     Silent mode.  If input is coming from a terminal, characters are not echoed.
              -t timeout
                     Cause  read  to  time out and return failure if a complete line of input is not read within
                     timeout seconds.  This option has no effect if read is not reading input from the  terminal
                     or a pipe.
              -u fd  Read input from file descriptor fd.

              If  no  names  are  supplied, the line read is assigned to the variable REPLY.  The return code is
              zero, unless end-of-file is encountered, read times out, or an invalid file descriptor is supplied
              as the argument to -u.