linux 學習隨筆-shell簡單編寫，隨筆-shell

linux 學習隨筆-shell簡單編寫，隨筆-shell

指令碼最好都放在/usr/local/sbin中

指令碼的執行 sh -x 指令碼.sh -x可以查看執行過程1在指令碼中使用變數 使用變數的時候，需要使用$符號： #!/bin/bash  ##把命令賦值為變數,需要使用反引號  d=`date +"%H:%M:%S"`  echo "The script begin at $d"  echo "Now we'll sleep 2 seconds"  sleep 2  d1=`date +"%H:%M:%S"`  echo "The script end at $d" 2在指令碼中使用數學運算要用[]括起來如下#! /bin/bash  a=1 b=2 ##數學運算用[]括起來 sum=$[$a+$b] echo "$a + $b = $sum" 3在指令碼中和控制台互動 使用read命令#! /bin/bash  read -p "Please input a number: " x read -p "Please input a number: " y sum=$[$x+$y] echo "The sum of the tow numbers is : $sum" 4shell中的預設變數#! /bin/bash  echo "$1 $2 $3 $0" 1 2 就是指令碼中的預設變數 一個指令碼中的預設變數是沒有限制的，0表示指令檔本書# sh option.sh 1 2 3 執行此命令輸出內容如下所示：1 2 3 option.sh 5shell中的邏輯判斷不帶else的if 注意if後面的判斷語句要用(())否則會報錯#! /bin/bash  read -p "Please input your score: " a if ((a<60)); then     echo "You didn't pass the exam." fi 5.1帶else 執行個體代碼如下#! /bin/bash  read -p "Please input your score: " a if ((a<60)); then     echo "You didn't pass the exam." else     echo "Good! You passed the exam." fi 5.2帶有else if(這是c中的說法)在shell中表示為elif#! /bin/bash  read -p "Please input your score: " a if ((a<60)); then     echo "You didn't pass the exam." elif ((a>=60)) && ((a<85)); then     echo "Good! You passed the exam." else     echo "Very good! Your score is very heigh" fi 5.3case 邏輯判斷#! /bin/bash  read -p "Input a number: " n a=$[$n%2] case $a in 1)     echo "The number is odd."     ;; 0)     echo "The number is even."     ;; *)     echo "It's not a number"     ;; esac * 表示其他值6for迴圈執行個體代碼如下：#! /bin/bash  for file in `ls`;do     echo $file done 7while 迴圈#! /bin/bash  a=5 while [ $a -ge 1 ]; do     echo $a     a=$[$a-1] done