Knowing these commands allows you to master shell's own tools

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The previous article was case driven , Sum up Sell The basic grammar in , This article takes you through case driven learning Sell The built-in tool commands in .

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Cut

cut The job of “ cut ”, Specifically, it is used to cut data in the file .cut Command to cut bytes from each line of a file 、 Characters and fields and put these bytes 、 Character and field output .

Basic usage

cut [ Option parameters ]  filename
#  The default separator is tab 

Parameter description

• -f ： Column number , Extract which column
• -d ： Separator , Splits columns according to the specified separator

Case study ：

First go to linux In the system , Prepare the data

Case study 1： cutting cat.txt First column

cut -f 1 -d " " cat.txt 

Case study 2： cutting cat.txt second 、 The three column

cut -f 2,3 -d " " cat.txt

Case study 3： stay cat.txt Cut out in file lisi

cat cat.txt | grep "lisi" | cut -f 1 -d " "

Sed

sed Is a flow editor , It processes one line at a time . When dealing with , Store the currently processed rows in a temporary buffer , be called “ Mode space ”, Then use sed Command processing buffer contents , After processing , Send the contents of the buffer to the screen . Next line , This is repeated , Until the end of the file . The contents of the document have not changed , Unless you use redirected storage output .

Basic usage

sed [ Option parameters ]  ‘command’  filename

Parameter description

• -e : Directly in command line mode sed Action editor

Command function

• a : newly added ,a You can use a string after , On the next line
• d : Delete
• s : Find and replace

Case study ：

Prepare the data

Case study 1： take “hello wawa” This word is inserted into sed.txt Second elements , Print

sed '2a hello wawa' sed.txt 

ps： The file hasn't changed

Case study 2： Delete sed.txt All files contain wo The line of

sed '/wo/d' sed.txt

Case study 3： take sed.txt In file wo Replace with ni

sed 's/wo/ni/g' sed.txt 

Awk

A powerful text analysis tool , Read the document line by line , Slice each line with a space as the default separator , The cut part is analyzed again .

Basic usage

awk [ Option parameters ] ‘pattern1{
    action1}  pattern2{
    action2}...’ filename
# pattern： Express AWK What to look for in the data , It's a matching pattern 
# action： A series of commands executed when a match is found 

Parameter description

• -F : Specify the input file separator
• -v : Assign a user-defined variable

Case study ：

Prepare the data

sudo cp /etc/passwd ./

Search for passwd Document to root All lines at the beginning of the keyword , And output the 7 Column .

awk -F: '/^root/{print $7}' passwd

awk Built in variables for

• FILENAME file name
• NR Number of records read
• NF The number of fields in the browsing record （ After cutting , Number of columns ）

Case study ：

Statistics passwd file name , Line number of each line , Columns per row

awk -F: '{print "filename:" FILENAME ", linenumber:" NR ",columns:" NF}' passwd 

Sort

sort The order is in Linux It's very useful , It sorts the files , And output the sorting result standard .

Basic grammar

sort( Options )( Parameters )

Parameter description

• -n Sort by the size of the value
• -r In reverse order
• -t Set the separator used for sorting
• -k Specify the columns to sort

Case study ：

Prepare the data

according to “：” The third column after splitting is sorted in reverse order

sort -t : -nrk 3 sort.sh 

This sharing ends here , I hope that's helpful .