2/15 (awk, awk conditions, awk processing design can perform additional tasks, and use awk array +for loop to realize advanced search)

awk

1, Pre instruction | awk Options Conditions Instructions
2,awk Options Conditions Instructions Processed documents
Options -F Define separator
Instructions print
Conditions / character string /
Built-in variables $1 First column $2 Second column $3 The third column …
$0 All columns NR Line number NF Column number

[[email protected] opt]# cat abc.txt # Prepare the material
hello the world
welcome to beijing

awk ‘{print}’ abc.txt # Output all
awk ‘/to/{print}’ abc.txt # The output is to Of course
awk ‘{print $2}’ abc.txt # Output the... Of all lines 2 Column
awk ‘/to/{print $1}’ abc.txt # The output is to The second line of the line 1 Column
awk ‘{print $0}’ abc.txt # Output all rows, all columns
awk ‘{print $0,$1}’ abc.txt # Output all rows, all columns , The first 1 Column
awk ‘{print NR}’ abc.txt # Output the line numbers of all lines
awk ‘{print NR,$0}’ abc.txt # Output the line numbers of all lines , All columns
awk ‘{print NR,NF}’ abc.txt # Output the line numbers of all lines , Column number ( How many columns )

awk ‘/^bin/{print NR}’ user # Find out bin Beginning line , Displays the line number of the line
awk ‘/^bin/{print NR,$0}’ user # Find out bin Beginning line , Displays the line number of the line , All columns
awk ‘{print NF}’ user # Output the column numbers of all rows （ There are several columns in each row ）
awk -F: ‘{print $1}’ user # If there are no spaces in the document , It can be used F Modify the separator
awk -F: ‘{print $1,$6}’ user # Use colons as column separators , According to the first 1、6 Column
awk -F: ‘{print $1" Our home directory is "$6}’ user # You can also output constants , Just add double quotation marks
awk -F: ‘{print $1" The interpreter is "$7}’ user

Collect the remaining capacity of the root partition
df -h | awk ‘//$/{print KaTeX parse error: Expected 'EOF', got '}' at position 2: 4}̲' # Use df -h …/{print “ The remaining capacity of the root partition is ”$4}’ # Then add a constant to output

Collect network card traffic information
ifconfig eth0 | awk ‘/RX p/{print “eth0 The amount of data received by the network card is ”$5" byte "}’
ifconfig eth0 | awk ‘/TX p/{print “eth0 The amount of data sent by the network card is ”$5" byte "}’

awk Conditions

1./ character string / You can also use regular ~ contain !~ It doesn't contain
awk -F: ‘$6~/root/{print}’ user # Output No 6 Column contains root The line of
awk -F: ‘$6~/bin/{print}’ user # Output No 6 Column contains bin The line of
awk -F: ‘$6!~/bin/{print}’ user # Output No 6 Column does not contain bin The line of

2. Use numbers or strings
== != > >= < <=
awk -F: ‘$3<3{print}’ user # Output No 3 Less than column 3 The line of
awk -F: ‘$3<=3{print}’ user # Output No 3 Column is less than or equal to 3 The line of
awk -F: ‘NR==2{print}’ user # Output No 2 That's ok
awk -F: ‘NR>2{print}’ user # The output line number is greater than 2 The line of

awk When to deal with it , Can perform additional tasks

BEGIN Mission perform 1 Time , Execute before reading the document
Line by line task perform n Time , Execute when reading a document
END Mission perform 1 Time , Execute after reading the document

utilize awk When to deal with it , Output the following


awk ‘BEGIN{print “User\tUID\tHome”}’ # The first 1 Step output header information
awk -F: ‘{print $1"\t"$3"\t"$6}’ user # The first 2 Step output content
awk ‘END{print “ A total of "NR" That's ok ” }’ user # The first 3 End of step output

awk -F: ‘BEGIN{print “User\tUID\tHome”}{print $1"\t"$3"\t"$6}END{print “ A total of "NR" That's ok ”}’ user # Write together

Use awk Array +for Loop to achieve advanced search

Array name [ Subscript ]= The value of the subscript
for( Variable name in Array name ){print Variable name } # This format can view all subscripts of the array
/var/log/httpd/access_log Check the records of accessing the website log

awk ‘{a[$1]++}END{for(i in a){print i,a[i]}}’ shu.txt # Collect documents using line by line tasks and arrays shu.txt Information in , And then in END Use... In tasks for Loop through all arrays a Subscript and value of

-n Is sorted in numerical form ,-r It's in descending order , -k Yes, specify which column to sort
awk ‘{ip[$1]++}END{for(i in ip){print i,ip[i]}}’ /var/log/httpd/access_log | sort -nr -k 2 # Use sort Command to add sorting function ,-n Is sorted in numerical form ,-r It's in descending order , -k Yes, specify which column to sort

/var/log/secure Is the security log , If someone enters the wrong password when logging in
The information will be recorded , This information can be used awk Grab it out , The method is as follows ：

Statistics of access in the security log root The account password is entered incorrectly ip Address and number