Shell script, awk condition judgment and logic comparison &||

Shell Script ,awk conditional if Compare with logic &&,||

O、 Some problems solved by conditional judgment ：
1、 Output all rows or partial rows ,
2、 Part of the data content of the output line ,
3、 Set multiple conditions

grammar ：
awk [ Options ]’[ Conditions ]{ Instructions }’ dir
Conditions can be filled in ： Regular expressions , The number / Character comparison , Logical comparison

One 、 Regular
~ matching ,!~ Mismatch
1、awk ‘/^ro/{print $1,$7}’ dir
With : For the separator , The print file contains ro The first and seventh columns of the first content line

2、awk -F: ‘$7!~/bash$/{print $1,$7}’ dir
With : For the separator , The seventh column in the specified file does not begin with bash The line at the end , Print its first and seventh columns

3、awk -F: ‘$7~/bash$/{print $1,$7}’ dir
With : For the separator , The seventh column in the specified file is marked with bash The line at the end , Print its first and seventh columns , If the number of columns $ There is no ~ If you receive regular, you will report a syntax error .

Two 、 The number , String comparison , image if But omitted if
== be equal to ,!= It's not equal to ,> Greater than ,>= Greater than or equal to ,< Less than ,<= Less than or equal to

1、awk ‘NR==2{print}’ dir
The print line number is 2 The content of the line

2、awk -F: ‘$7!="/bin/bash"’ dir
With : Separator , Print the seventh column string, which is not "/bin/bash" All line contents of the line of

3、awk -F: ‘$3>=1000{print $1}’ dir
With : Separator , Print the third column of numbers greater than or equal to 1000 The first column of the row content of

4、awk ‘NR%2==0’ dir
Print the contents of all even lines of the specified file

3、 ... and 、、 Logical comparison
&& Logic and
awk -F: ‘$3>=0&&$3<2{print $1,$3}’ /etc/passwd
With : Separator , Print the third column of numbers greater than or equal to 0, And less than 2 The first and third columns of the row of .

|| Logic or
awk -F: ‘$30||$32{print $1,$3}’ /etc/passwd
With : Separator , Print the third column of numbers equal 0, Or equal to 2 The first and third columns of the row of .