在Linux下，我們經(jīng)常會(huì)使用grep對一些結(jié)果進(jìn)行過過濾，下面簡單介紹一個(gè)grep和正則表達(dá)式結(jié)合的用法。
源文件如下：

     1  "Open Source" is a good mechanism to develop programs.$
     2  apple is my favorite food.$
     3  Football game is not use feet only.$
     4  this dress doesn't fit me.$
     5  However, this dress is about $ 3183 dollars.^M$
     6  GNU is free air not free beer.^M$
     7  Her hair is very beauty.^M$
     8  I can't finish the test.^M$
     9  Oh! The soup taste good.^M$
    10  motorcycle is cheap than car.$
    11  This window is clear.$
    12  the symbol '*' is represented as start.$
    13  Oh!^IMy god!$
    14  The gd software is a library for drafting programs.^M$
    15  You are the best is mean you are the no. 1.$
    16  The world <Happy> is the same with "glad".$
    17  I like dog.$
    18  google is the best tools for search keyword.$
    19  goooooogle yes!$
    20  go! go! Let's go.$
    21  # I am VBird$
    22  $

• 查找特定字符串

  • 查找the這個(gè)特定字符串：grep -n 'the' regular_express.txt
  grep -n 'the' regular_express.txt

  • 查找不包含the這個(gè)字符的行：grep -vn 'the' regular_express.txt
    

    grep -vn 'the' regular_express.txt

  • 忽略大小寫查找包含the的行：grep -in 'the' regular_express.txt
    

    grep -in 'the' regular_express.txt

• 利用中括號[]來查找集合字符

  • 比如我想查找test或者taste這兩個(gè)單詞時(shí)，可以這么寫：grep -n 't[ae]st' regular_express.txt （不論方括號里面有幾個(gè)字符，它都只代表一個(gè)字符
    

    grep -n 't[ae]st' regular_express.txt

  • 如果不想要oo前面有g(shù)的話，可以這么寫：grep -n '[^g]oo' regular_express.txt （[^g]中的^表示反向選擇，即表示oo前面不能是g）
    

    grep -n '[^g]oo' regular_express.txt

  • 假如我oo前面不能有小寫字符：grep -n '[^a-z]oo' regular_express.txt （a-z就表示小寫字符，還有另外一種寫法使用特殊字符[:lower:],這個(gè)也是表示小寫字母-grep -n '[^[:lower:]]oo' regular_express.txt）
    

    grep -n '[^a-z]oo' regular_express.txt

• 行首和行尾字符^ 和 $

  • 查找到一行中行首為the的：grep -n '^the' regular_express.txt
    

    grep -n '^the' regular_express.txt

  • 查找不以小寫字符開頭的：grep -n '^[a-z]' regular_express.txt（這里需要注意^ 在[]的里面和外面是兩個(gè)不同的概念，在[]里面表示反向選擇，在[]外面表示定位在行首的意義）
    

    grep -n '^[^a-z]' regular_express.txt

  • 查找行尾是. d的： grep -n '.$' regular_express.txt, 這里有兩個(gè)點(diǎn)需要注意第一是小數(shù)點(diǎn).之前有一個(gè)轉(zhuǎn)移符，這是因?yàn)?具有其他意義，因此需要使用轉(zhuǎn)移符\來消除其特殊意義。第二點(diǎn)就是文件中的第5-9行并沒有被打印出來。我們?nèi)绻屑?xì)看源文件的話或發(fā)現(xiàn)第5-9行的結(jié)尾是.^M$,這里涉及到一個(gè)Linux和windows的斷行字符的問題，Linux是以LF（\n）斷行，而windows是以CRLF（\r\n）斷行，所以一般我們在Linux上面查看windows的文件，其結(jié)尾都是^M，所以我們在windows下編寫的腳本放到Linux上運(yùn)行之前需要小心，要去除掉這個(gè)字符，不然運(yùn)行會(huì)報(bào)錯(cuò)。
    

    grep -n '.$' regular_express.txt