Bash Learning Notes

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Reference: http://vbird.dic.ksu.edu.tw/linux_basic/0340bashshell-scripts.php
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1. $*, $@, $#, $, $, $?


The script name is called test.sh Three: 1 2 3
After running test.sh 1 2 3
$* is "1 2 3" (enclosed in quotes)
$@ for "1" "2" "3" (wrapped separately)
$ #为3 (number of parameters)
$: Script Full Name
$: First parameter


$ usage: If you find that the command on the previous line is executing incorrectly, the script terminates execution
If [$?-ne 0];then
Fatal_log "Fail execute!"
Exit 1
Fi




2. datefmt= ' Date +%y%m%d '
Echo $datefmt #20141209

datefmt= ' Date +%y%m%d-d '-1 day '
Echo $datefmt #20141208

3. Awk-f "" ' Nr==fnr{a[$1]=1}nr>fnr{if (a[$1]) {print $1,$2, "1";} Else{print $1,$2, "0";}} ' A.txt B.txt

which

A.txt:

Guomei
Nginx
Hello
World

B.txt:

Nginx
Hello
World

Results:

Nginx 1
Hello 1
World 0

4. Awk-f "' $ ~/name=dash/{print $} ' 20141001.log

Usage instructions

5. Statistics the sum of the second column (one column, two Columns tab split)

ABC 12

DDD 234

XYZ 87

Cat Test.txt | Awk-f "T" ' Begin{sum=0}{sum+=$2}end{print sum} '

6. Press the second column to go heavy

awk ' {!a[$2]++} '

Reference: http://bbs.chinaunix.net/thread-1837787-1-1.html

Principle:

awk syntax: awk ' pattern{action} ', action defaults to print

So the above statement equates to: awk '!a[$2]{print $0;a[$2]++} '

7. Find two file difference sets

Grep-f-v-f B.txt A.txt | Sort | Uniq

It's a-b.

Reference: http://blog.csdn.net/autofei/article/details/6579320

8. $var, ${var}, ${#var},$ (arithmetic expression)

$var, ${var} returns the value of the variable, but ${var} to ambiguity

${#var} return length

$ ((1+2*5)) return 11

9 du-s./* | Sort-nr

Lists the file (folder) size in the current directory, descending order, rather than recursively calculating the file size

10.shell can you read one row of the contents of a file and then split the read line and put it in the array

Http://bbs.chinaunix.net/thread-4117251-1-1.html

11. In the first column + The second column key, calculates the third row and

Tom Kobe 13

Jack John 22.

Tom Kobe 57

Cat File.txt | Awk-f "" ' {a[$1 ' "" $2]+=$3}end{for (i in a) {print I ' a[i]} '