awk & sed
=========

sed
---

.. versionadded:: @2019-01-26
   创建

替换 HEX 表示的字符
^^^^^^^^^^^^^^^^^^^

    `printf '\xC2\xA0\n' | sed 's/\xc2\xA0/X/g'`

替换整行的例子
^^^^^^^^^^^^^^

::

    $ printf 'a\nb\n' | sed "s/a.*/aaa/g"
    aaa
    b
    $ printf 'a\nb\n' | sed "/a.*/c\aaa"
    aaa
    b
    $ printf 'a\nb\n' | sed 's/\(a\).*/\1"xxx"/g'
    a"xxx"
    b

替换换行符
^^^^^^^^^^

::

  $ printf 'a\nb\n' | sed ':a;N;$!ba;s/\n/ /g' | hexdump -C
  00000000  61 20 62 0a                                       |a b.|
  00000004

解释：

#. Create a label via :a.
#. Append the current and next line to the pattern space via N.
#. If we are before the last line, branch to the created label
   $!ba ($! means not to do it on the last line as there should
   be one final newline).
#. Finally the substitution replaces every newline with a space
   on the pattern space (which is the whole file).

awk
---

* 删除重复的行 (不需要排序

  `awk '!x[$0]++' <file>`