13、 Command gadget

13、 ... and 、 Command gadget

cut： Column interceptor

Instructions :cut Command to cut bytes from each line of a file 、 Characters and fields and put these bytes 、 Write characters and fields to standard output . If you don't specify File Parameters ,cut Command will read standard input . Must specify -b、-c or -f One of the signs

Options ：

-b	Intercept by byte
-c	Intercept by character , Commonly used in Chinese
-d	Specify what to use as the delimiter to intercept , The default is tab
-f	Usually and -d Together

[[email protected] ~]# cat /etc/passwd | cut -d':' -f 1
                  # Intercept /etc/passwd In the following ： Split the first string 
[[email protected] ~]# cat /etc/passwd | cut -d':' -f 3
                  # Intercept /etc/passwd In the following ： Split the third string 
[[email protected] ~]# cat /etc/passwd | cut -d':' -f1,3
                  # Intercept /etc/passwd In the following ： Split the second 1 And 3 A string 
[[email protected] ~]# cat /etc/passwd | cut -d':' -f1-3
                  # Intercept /etc/passwd In the following ： Split the first to three strings 
[[email protected] ~]# who | cut -b 3   # Intercept the third byte 
[[email protected] ~]# who | cut -c 3   # Intercept the third character , It can be used to intercept Chinese 
[[email protected] ~]# cat name | cut -b 2
[[email protected] ~]# cat name | cut -c 2

Be careful ：cut Only good at dealing with text separated by a single character

sort

It is a tool to sort the contents of files in behavioral units , It can also be sorted according to different data types . For example, the sorting of data and characters is different

sort [ Options ]  Parameters 

Common options

-t	Specify the separator , By default [Tab] Well Key or space separation
-k	Specify sorting area , Which interval is sorted
-n	Sort by number , The default is to sort in text
-u	Equate to uniq, Indicates that only one row of the same data is displayed , Be careful ： If there is a space at the end of the line, de duplication will not succeed
-r	Reverse sorting , The default is ascending ,-r It's descending
-o	Transfer the sorted results to the specified file

sort passwd.txt    // Without any options, it is in ascending order of the first column by default , Letters are from a To z From above 

sort -n -t: -k3 passwd.txt    // Use colon as separator , Sort the third column by number size （ Ascending ）

sort -nr -t: -k3 passwd.txt   // Use colon as separator , Sort the third column by number size （ Descending ）

sort -nr -t: -k3 passwd.txt -o passwd.bak    // Output the input results not on the screen, but to passwd.bak file 

sort -u passwd.txt    // Remove duplicate lines from the file （ Repeated lines can be discontinuous ）

uniq

It is mainly used to remove continuous repeated lines
Be careful ： Is a continuous line , So usually with sort Combined with the use of sorting to make it a continuous row, and then perform the de duplication operation , Otherwise, he can't repeat the discontinuous lines

uniq [ Options ]  Parameters 

Common options

-c	Count duplicate rows ;
-d	Show only duplicate lines ;
-u	Show only rows that appear once

uniq -c    // Count the number of repeated lines , He doesn't count as a repeating line 
sort | uniq -c   // combination sort Use 
sort | uniq -d   // combination sort Use , Filter out duplicate lines 
sort | uniq -u    // combination sort Use , Filter out non duplicate lines 

example ： View logged in users

example ： Check the users who have logged in to the system

tr

It can replace one character with another , Or you can completely remove some characters , You can also use it to remove duplicate characters

tr [ Options ]… SET1 [SET2]
 Replace... From standard input 、 Downsizing and / Or delete characters , And write the results to standard output .

Common options

-d	Delete character
-s	Delete all duplicate characters , Keep only the first

 tr 'a-z' 'A-Z'        # Replace lowercase content with uppercase 
 tr 'apple' 'APPLE'    # Substitution is the substitution of one-to-one letters 
 tr 'a' ' '            # Enclose the replaced characters in single quotation marks , Include special characters , The character a Delete 
 tr 'a' '/'            # take a Replace with /
 tr 'ap' '/'           # Replace multiple characters with one , take a and p Replace with /
 tr 'apple' 'star'     #a Replace with s,p Replace with a,le Replace with r
 tr -d 'a'             # Delete all a
 tr "'" '/'            # If you want to replace the single quotation mark, you need to enclose the single quotation mark with double quotation marks , Backslash escape doesn't work 
 tr -d 'apple'         # Put everything that contains this 5 Delete all letters 
 tr -s 'p'             # Yes p Character de duplication , Keep only the first 
 tr -s '\n'            # When multiple carriage returns are encountered, only one carriage return is reserved , Equivalent to removing empty lines 

1. Count the number of currently connected hosts

[[email protected] opt]# ss -nt | tr -s " " | cut -d " " -f5 | cut -d ":" -f1 | sort | uniq -c
      1 20.0.0.1
      1 Address

2. Count the connection status of the current host

[[email protected] opt]# ss -nta | grep -v '^State' | cut -d" " -f1 | sort | uniq -c
      1 ESTAB
     19 LISTEN

2. Count the connection status of the current host

[[email protected] opt]# ss -nta | grep -v '^State' | cut -d" " -f1 | sort | uniq -c
      1 ESTAB
     19 LISTEN