Linux shell命令(2) - cat/cut/paste/sed/tr/grep/sort/uniq

who

• all users currently logged in to the system

cat

• examine the contents of a file

wc -l

wc -w

wc -c

• get a count of the total number of lines, words, and characters of information contained in a file

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cut

cut -cchars file

$ who

root     console Feb 24 08:54

steve    tty02   Feb 24 12:55

george   tty08   Feb 24 09:15

dawn     tty10   Feb 24 15:55

$ who | cut -c1-8       Extract the first 8 characters

root

steve

george

dawn

$

$ who | cut -c1-8,18-

root     Feb 24 08:54

steve    Feb 24 12:55

george   Feb 24 09:15

dawn     Feb 24 15:55

$

-d and -f options

以-d指定分界符将参数分成多个field，-f指定哪几个field

不指定分界符，则以tab为分界符

$ cat /etc/passwd

root:*:0:0:The Super User:/:/usr/bin/ksh

cron:*:1:1:Cron Daemon for periodic tasks:/:

bin:*:3:3:The owner of system files:/:

uucp:*:5:5::/usr/spool/uucp:/usr/lib/uucp/uucico

asg:*:6:6:The Owner of Assignable Devices:/:

steve:*:203:100::/users/steve:/usr/bin/ksh

other:*:4:4:Needed by secure program:/:

$ cut -d: -f1 /etc/passwd     Extract field 1

root

cron

bin

uucp

asg

steve

other

$ cut -d: -f1,6 /etc/passwd   Extract fields 1 and 6

root:/

cron:/

bin:/

uucp:/usr/spool/uucp

asg:/

steve:/users/steve

other:/

$

 

grep 

grep pattern files  搜索模式串

*， ？都可运用到模式串和文件名

正则表达式例子：

grep '[A-Z]' list	Lines from list containing a capital letter
grep '[0-9]' data	Lines from data containing a number
grep '[A-Z]...[0-9]' list	Lines from list containing five-character patterns that start with a capital letter and end with a digit
grep '\.pic$' filelist	Lines from filelist that end in .pic

grep –i  忽略匹配大小写

grep -v   找出不匹配模式串的行

grep -l    仅列出包含模式串的文件

grep -n  额外给出匹配的行号

sort 

排序

sort -u  去除重复项

sort -r   逆向排序

sort -o  重定向到文件  sort names -o sorted_names 等价于 sort names -o > sorted_names

sort -n 算术排序，而非字符排序

sort +1n 跳过第1个field，然后算术排序

sort -t 指定分界符来分隔field,通常sort +1n这类都默认以space或tab为分隔符