HOST="google.com"ping -c1$HOST # -c is usedforcount, it will send the request, number of times mentionedRETURN_CODE=$? # 最后运行的命令的结束代码(返回值)即执行上一个指令的返回值if["$RETURN_CODE"-eq"0"]thenecho"$HOST reachable"elseecho"$H...
-z STRING # True if STRING is empty -n STRING # True if STRING is not empty STRING1 = STRIN2 # True if strings are equal STRING1 != STRIN2 # True if strings are not equal 算术测试操作 var1 -eq var2 # True if var1 is equal to var2 var1 -ne var2 # True if var1 not eq...
The operator return an exit code 0 (True) if the strings match the regular expression regex. The $BASH_REMATCH environment variable is a read-only Bash Array containing the values matched by the extended regular expression at the right side of the =~ binary operator in a double-bracket [[...
#!/usr/bin/env bash # File: whileloop.sh count=3 while [[ $count -gt 0 ]] do echo "count is equal to $count" let count=$count-1 done WHILE循环首先以while关键字开头,然后是一个条件表达式。只要循环迭代开始时条件表达式等价于true,那么WHILE循环中的代码将继续执行。当我们运行这个...
return the exit status of thelastcommand exe‐22cuted from filename. If filename does not contain a slash, filenamesinPATH are used tofindthe directory containingfile‐23name, but filename does not need to be executable. ThefilesearchedforinPATH need not be executable. When bash is not24in...
bashsimpleif.sh 77 ## Start program ## End program We provided the argument77, however 77 is not equal to 4, therefore the code within the IF statement was once again skipped. Finally let’s provide4as an argument: bashsimpleif.sh 4 ...
printf '%s ' "${arr[${i:=0}]}" ((i=i>=${#arr[@]}-1?0:++i)) } 1. 2. 3. 4. 5. 6. 在两个值之间切换 这与上面的工作方式相同,这只是一个不同的用例。 arr=(true false) cycle() { printf '%s ' "${arr[${i:=0}]}" ...
Define a function "check_user_existence()" to check if the given user exists on the system. Inside the function: Use the "id" command to check if the user exists. If the user exists, the "id" command will return successfully (exit code 0), otherwise, it will return an error (exit...
Code: #!/bin/bash # Function to check if a number is prime is_prime() { local num=$1 # Check if the number is less than 2 (not prime) if (( num < 2 )); then echo false return fi # Check divisibility from 2 to the square root of the number ...
的结果: anny > grep $USER /etc/passwd anny > if [ $? −ne 0 ] ; then echo "not a local account" ; fi not a local account anny > 58/91 Bash 新手指南 7.1.2.2.数字的比较 以下的例子是用了数值的比较: anny > num=`wc −l work.txt` anny > echo $num 201 anny > if [ "...