Introduction to Linux awk and shell variable delivery __linux

First, awk uses ordinary variables in the shell
Method 1: Use the quotation mark method
Aa= "Hello"
awk ' BEGIN {print ' $aa '} '
Output $AA
awk ' BEGIN {print ' $aa '} '
Output Hello
awk ' BEGIN {print ' ' $aa '} '
Output empty


Aa= "hello! Coder "
awk ' BEGIN {print ' $aa '} '
Error, double quotes do not match, because space appears in the middle
awk ' BEGIN {print ' ' $aa ' '} '
Hello! can be displayed normally Coder


Method 2: Using the-V method
Awk-v varaa= "$aa" ' BEGIN {print Varaa} '
Awk-v varaa= $aa ' BEGIN {print Varaa} '
Can be normal display,-V or more convenient, more clear


Method 3: Through environment variables
Aa= "This is a test"; Export AA
awk ' begin{print environ[' AA ']} '
Normal
Note that setting the environment variable is export AA rather than export $AA


Method 4: Use awk ' script ' awkvar= ' shellvar ' filename
Aa= "This is a test"; Export AA
awk ' end{print BB ' bb= "$aa" a.txt
When the end is changed to begin, it cannot be used.


An array variable using the shell in awk
Aa= (a b c D e)
Awk-v bb= "$aa" ' Begin{print BB} '
Can only output a, estimated to be the first member of the array AA
Aa= (a b c D e)
Awk-v bb= "$aa" ' begin{for (i in BB) print Bb[i]} '
Error
Hint BB is not an array


Aa= (a b c D e)
Awk-v bb= "${aa[*]}" ' Begin{split (Bb,a, ""); for (i in A) print I "---" A[i]} '


Using the array in awk in the shell
Note: The array in the shell is an associative array, the subscript can only be a number, and the array in awk is an associative array, and the subscript can be a string
The variable name that awk defines in begin cannot be called index


Eval $ (awk ' BEGIN {xiabiao=0} {aa[$1]=$2} end{for (i in AA) {print ' aa[' Xiabiao ']= ' aa[i];xiabiao+=1}} ' A.txt)
echo ${#aa [@]}
Echo ${aa[@]}