The fifth lesson in six weeks (May 3)
reviews the use of external shell variables in
extended awk http://ask.apelearn.com/question/199 
Relatively speaking, awk is more like a simple programming language
A=44echo "ABCD" | awk -v GET_A=$A '{print GET_A}'
Description: The -v option is used to define parameters, which means that the value of variable A is assigned to GET_A.
As many variables need to be assigned, as many -v options are required. Equivalent to: Applied to a script:
Awk merges a file http://ask.apelearn.com/question/493
I have such a requirement, I need to merge the same lines in the first column of two files into the same line. For example, there are two files with the following content:
cat 1.txt
1 aa
2 bb
3 ee
4 ss
cat 2.txt
1 ab
2 cd
3 ad
4 bd
5 de
The combined result is:
1 ab aa
2 cd bb
3 The command implemented by ad ee
4 bd ss
5 de
is:
awk 'NR==FNR{a[$1]=$2}NR>FNR{print $0,a[$1]}' 1.txt 2.txt
This involves
Explanation: NR represents the number of lines read, and FNR represents the current number of lines read,
so in fact, NR==FNR means when 2.txt is read. Similarly, NR>FNR means that when reading 1.txt, the
array a is actually equivalent to a map connecting multiple lines of a file into one line http://ask.apelearn.com/question/266
The use of the gsub function in awk http: //ask.apelearn.com/question/200
awk intercepts multiple specified domains into one line http://ask.apelearn.com/question/224
Filters two or more keywords http://ask.apelearn.com/ question/198
Generate the following structured file with awk http://ask.apelearn.com/question/5494
awk print single quotes with print http://ask.apelearn.com/question/1738
Merge two files http://ask .apelearn.com/question/945
Reference tutorial for awk http://www.cnblogs.com/emanlee/p/3327576.html