- Using external shell variables in awk http://ask.apelearn.com/question/199
Test file awk.txt
及格:张三:67
不及格:李四:58
及格:小明:72
优秀:小虎:95
不及格:小兰:49
编写脚本awk1.sh：
#!/bin/bash
sort -n awk.txt|awk -F ":" '{print $1}'|uniq >考试.txt
sort awk.txt|awk -F ":" '{print $1}'|uniq -c >123.txt
for a in `cat 考试.txt`;do
echo "[$a]":`awk -v c=$a '$2==c {print $1}' 123.txt`人
awk -v b=$a -F ":" '{OFS=":"} $1==b {print $2,$3}' awk.txt
done
[root@linux-128 test]# sh awk1.sh
[不及格]:2人
李四:58
小兰:49
[及格]:2人
张三:67
小明:72
[优秀]:1人
小虎:95
- Note: The -v option is used to define parameters, here it means assigning the value of variable a to b
- As many variables need to be assigned, as many -v options are required. Applied to the 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 contents
[root@linux-128 awk]#cat 1.txt
1 aa
2 bb
3 ee
4 ss
[root@linux-128 awk]#cat 2.txt
1 ab
2 cd
3 ad
4 bd
5 de
[root@linux-128 awk]# awk 'NR==FNR{a[$1]=$2}NR>FNR{print $0,a[$1]}' 1.txt 2.txt
1 ab aa
2 cd bb
3 ad ee
4 bd ss
5 de
- 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
- Concatenate multiple lines of a file into one http://ask.apelearn.com/question/266 Example:
[root@linux-128 awk]#cat 2.txt
1 ab
2 cd
3 ad
4 bd
5 de
Difference between print and printf
[root@linux-128 awk]# awk '{print $1}' 2.txt
1
2
3
4
5
[root@linux-128 awk]# awk '{printf $1}' 2.txt
12345[root@linux-128 awk]# ^C
The effect of echo "" is a newline
[root@linux-128 awk]# awk '{printf $1}' 2.txt; echo""
12345
print keeps the original format printing, printf cancels all format printing, you can define the format to print.
[root@linux-128 awk]# awk '{printf ("%s+",$1)}' 2.txt;echo ""
1+2+3+4+5+
We can use sed to achieve this requirement
[root@linux-128 awk]# cat 2.txt|awk '{print $1}'|xargs|sed -r 's/ /+/'g
1+2+3+4+5
- The use of gsub function in awk http://ask.apelearn.com/question/200
The use of gsub function in awk
The replacement function in gsub and sed is similar
- use gsub
[root@linux-128 awk]# cat 1.txt
1 aa
2 bb
3 ee
4 ss
[root@linux-128 awk]# awk 'gsub(/[0-9]/,"abc")' 1.txt
abc aa
abc bb
abc ee
abc ss
- Use sed to replace
[root@linux-128 awk]# sed 's/[0-9]/abc/g' 1.txt
abc aa
abc bb
abc ee
abc ss
- awk 'gsub(/[0-9]/,"abc",$1) {print $0}' 1.txt // replace the number in $1 with abc
[root@linux-128 awk]# awk 'gsub(/[0-9]/,"abc",$1) {print $0}' 1.txt
abc aa
abc bb
abc ee
abc ss