我将man djpeg的输出重定向到一个文本文件中，以便在学习使用它时可以参考它。我的指令是man djpeg > textfile.txt。然而，输出如下所示：

LS(1)                     BSD General Commands Manual                    LS(1)

NNAAMMEE
     llss -- list directory contents

SSYYNNOOPPSSIISS
     llss [--AABBCCFFGGHHLLOOPPRRSSTTUUWW@@aabbccddeeffgghhiikkllmmnnooppqqrrssttuuwwxx11] [_f_i_l_e _._._.]

DDEESSCCRRIIPPTTIIOONN
     For each operand that names a _f_i_l_e of a type other than directory, llss
     displays its name as well as any requested, associated information.  For
     each operand that names a _f_i_l_e of type directory, llss displays the names
     of files contained within that directory, as well as any requested, asso-
     ciated information.

     If no operands are given, the contents of the current directory are dis-
     played.  If more than one operand is given, non-directory operands are
     displayed first; directory and non-directory operands are sorted sepa-
     rately and in lexicographical order.

     The following options are available:

     --@@      Display extended attribute keys and sizes in long (--ll) output.

     --11      (The numeric digit ``one''.)  Force output to be one entry per
             line.  This is the default when output is not to a terminal.

     --AA      List all entries except for _. and _._..  Always set for the super-
             user.

     --aa      Include directory entries whose names begin with a dot (_.).

     --BB      Force printing of non-printable characters (as defined by
             ctype(3) and current locale settings) in file names as \_x_x_x,
             where _x_x_x is the numeric value of the character in octal.

     --bb      As --BB, but use C escape codes whenever possible.

[...continues]

还有更多，但你明白了。为什么它重复一些字符？还有，如果有一些函数执行两次或缓存刷新不正确，为什么它不重复所有字符？