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

 

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指定分界符將參數分成多個field，-f指定哪幾個field

不指定分界符，則以tab為分界符

$ 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  搜尋模式串

*， ？都可運用到模式串和檔案名稱

Regex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  忽略匹配大小寫

grep -v   找出不匹配模式串的行

grep -l    僅列出包含模式串的檔案

grep -n  額外給出匹配的行號

sort 

排序

sort -u  去除重複項

sort -r   逆向排序

sort -o  重新導向到檔案  sort names -o sorted_names 等價於 sort names -o > sorted_names

sort -n 算術排序，而非字元排序

sort +1n 跳過第1個field，然後算術排序

sort -t 指定分界符來分隔field,通常sort +1n這類都預設以space或tab為分隔字元