Linux下的sort命令默认将文件中的每一行为单位，进行排序，然后输出。具体地，就是从每行的第一个字符开始，依次按ASCII码值进行比较，最后将结果按升序排序输出。
1、sort常用选项
- -u 在排序的时候忽略相同的行，类似于uniq命令，不过uniq命令只能跳过相邻的相同行，并不能进行排序。
- -n 按照数字大小排序，而不是文本的ascii码顺序。
- -r 反序，也就是降序。
- -t 指定列分隔符，注意这里的分隔符只能是一个字符，不能是多个字符，-t, --field-separator=SEP use SEP instead of non-blank to blank transition，默认以非空到空的分隔作为列分隔符。
- -k 指定排序关键字的列。
- -s 有时候，sort会在根据指定字段排完序之后，自动根据其他字段进行resort，为了保证原来的数据记录的顺序，可以使用-s选项来禁止sort命令的resort机制。
这里的-k选项比较复杂，这里单独说一下-k后面指定参数的格式：
FStart.CStartModifier,FEnd.CEndModifier
开始部分 , 结束部分
-k选项用来指定排序的关键字列，也就是排序依据的字段。-k后的参数格式大致分为两个部分，开始部分和结束部分。开始部分中又可以看出三个参数：FStart、CStart和Modifier，其中FStart表示第第几列（FStart表示Field Start，也就是这个值用来指定排序依据所开始的列，列的序号从1开始，不是程序猿通常习惯的0），CStart表示第几个字符（Character Start，就是说这个值用来说明排序依据从该列的第几个字符开始，如果没有指定，默认从第一个字符开始），Modifier就是n、r等指定数值排序、逆序等的选项。与开始部分类似，结束部分也有三个参数：FEnd、CEnd和Modifier，其中FEnd就是指定排序依据到第几列结束，CEnd指定排序依据到该列的第几个字符结束，如果省略或者指定为0，则默认到该域的最后一个字符，Modifier的含义和开始部分一样。
注意，如果没有开始部分，则默认从行首开始，如果省略结束部分，则默认到行末结束。
2、例子
这里的例子用下面的文件作为例子：
$ cat name_list.txt
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
Abbie Cornishi:female:actor:19820807:1.73m:Klondike
Hara Mikie:female:pictorial model:19870703:1.62m:Oscar Promotion Co., Ltd.
Drew Barrymore:female:actor:19750222:1.63m:Music and Lyrics
Kobe Bryant:male:NBA player:19780823:1.98m:Los Angeles Lakers
Timothy Theodore Duncan:male:NBA player:19760425:2.11m:San Antonio Spurs
Tony Parker:male:NBA player:19820517:1.88m:San Antonio Spurs
Manu Ginóbili:male:NBA player:19770728:1.98m:San Antonio Spurs
LaMarcus Nurae Aldridge:male:NBA player:19850719:2.11m:Portland Trail Blazers
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
$
2.1 常见的r，u，n选项的使用
$ sort name_list.txt
Abbie Cornishi:female:actor:19820807:1.73m:Klondike
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
Drew Barrymore:female:actor:19750222:1.63m:Music and Lyrics
Hara Mikie:female:pictorial model:19870703:1.62m:Oscar Promotion Co., Ltd.
Kobe Bryant:male:NBA player:19780823:1.98m:Los Angeles Lakers
LaMarcus Nurae Aldridge:male:NBA player:19850719:2.11m:Portland Trail Blazers
Manu Ginóbili:male:NBA player:19770728:1.98m:San Antonio Spurs
Timothy Theodore Duncan:male:NBA player:19760425:2.11m:San Antonio Spurs
Tony Parker:male:NBA player:19820517:1.88m:San Antonio Spurs
$ sort -u name_list.txt
Abbie Cornishi:female:actor:19820807:1.73m:Klondike
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
Drew Barrymore:female:actor:19750222:1.63m:Music and Lyrics
Hara Mikie:female:pictorial model:19870703:1.62m:Oscar Promotion Co., Ltd.
Kobe Bryant:male:NBA player:19780823:1.98m:Los Angeles Lakers
LaMarcus Nurae Aldridge:male:NBA player:19850719:2.11m:Portland Trail Blazers
Manu Ginóbili:male:NBA player:19770728:1.98m:San Antonio Spurs
Timothy Theodore Duncan:male:NBA player:19760425:2.11m:San Antonio Spurs
Tony Parker:male:NBA player:19820517:1.88m:San Antonio Spurs
$ sort -r name_list.txt
Tony Parker:male:NBA player:19820517:1.88m:San Antonio Spurs
Timothy Theodore Duncan:male:NBA player:19760425:2.11m:San Antonio Spurs
Manu Ginóbili:male:NBA player:19770728:1.98m:San Antonio Spurs
LaMarcus Nurae Aldridge:male:NBA player:19850719:2.11m:Portland Trail Blazers
Kobe Bryant:male:NBA player:19780823:1.98m:Los Angeles Lakers
Hara Mikie:female:pictorial model:19870703:1.62m:Oscar Promotion Co., Ltd.
Drew Barrymore:female:actor:19750222:1.63m:Music and Lyrics
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
Abbie Cornishi:female:actor:19820807:1.73m:Klondike
$ sort -ru name_list.txt
Tony Parker:male:NBA player:19820517:1.88m:San Antonio Spurs
Timothy Theodore Duncan:male:NBA player:19760425:2.11m:San Antonio Spurs
Manu Ginóbili:male:NBA player:19770728:1.98m:San Antonio Spurs
LaMarcus Nurae Aldridge:male:NBA player:19850719:2.11m:Portland Trail Blazers
Kobe Bryant:male:NBA player:19780823:1.98m:Los Angeles Lakers
Hara Mikie:female:pictorial model:19870703:1.62m:Oscar Promotion Co., Ltd.
Drew Barrymore:female:actor:19750222:1.63m:Music and Lyrics
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
Abbie Cornishi:female:actor:19820807:1.73m:Klondike
2.2 -k字段的使用
（1）根据人名列表中出生年份字段排序
出生年份就是出生年月的前四个字符。
$ sort -t : -k 4,4.4n name_list.txt
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
Drew Barrymore:female:actor:19750222:1.63m:Music and Lyrics
Timothy Theodore Duncan:male:NBA player:19760425:2.11m:San Antonio Spurs
Manu Ginóbili:male:NBA player:19770728:1.98m:San Antonio Spurs
Kobe Bryant:male:NBA player:19780823:1.98m:Los Angeles Lakers
Abbie Cornishi:female:actor:19820807:1.73m:Klondike
Tony Parker:male:NBA player:19820517:1.88m:San Antonio Spurs
LaMarcus Nurae Aldridge:male:NBA player:19850719:2.11m:Portland Trail Blazers
Hara Mikie:female:pictorial model:19870703:1.62m:Oscar Promotion Co., Ltd.
（2）根据人名列表中出生月份字段排序
出生月份就是人名列表中出生年月字段的第5到第6字符。
$ sort -t : -k 4.5,4.6n name_list.txt
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
Drew Barrymore:female:actor:19750222:1.63m:Music and Lyrics
Timothy Theodore Duncan:male:NBA player:19760425:2.11m:San Antonio Spurs
Tony Parker:male:NBA player:19820517:1.88m:San Antonio Spurs
Hara Mikie:female:pictorial model:19870703:1.62m:Oscar Promotion Co., Ltd.
LaMarcus Nurae Aldridge:male:NBA player:19850719:2.11m:Portland Trail Blazers
Manu Ginóbili:male:NBA player:19770728:1.98m:San Antonio Spurs
Abbie Cornishi:female:actor:19820807:1.73m:Klondike
Kobe Bryant:male:NBA player:19780823:1.98m:Los Angeles Lakers
（3）根据身高排序
$ sort -t : -k 5,5.4n name_list.txt
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
aName:aGender:aProfession:aBirthday:aHeight:aEtc.
Hara Mikie:female:pictorial model:19870703:1.62m:Oscar Promotion Co., Ltd.
Drew Barrymore:female:actor:19750222:1.63m:Music and Lyrics
Abbie Cornishi:female:actor:19820807:1.73m:Klondike
Tony Parker:male:NBA player:19820517:1.88m:San Antonio Spurs
Kobe Bryant:male:NBA player:19780823:1.98m:Los Angeles Lakers
Manu Ginóbili:male:NBA player:19770728:1.98m:San Antonio Spurs
LaMarcus Nurae Aldridge:male:NBA player:19850719:2.11m:Portland Trail Blazers
Timothy Theodore Duncan:male:NBA player:19760425:2.11m:San Antonio Spurs
到这里，指定字段的方法应该就说完了，以后用到更加复杂的仍会贴在这里。