This will test whether the variable$foois equal to the string*ar. It will work even if$foois empty because the quotation marks will force an empty string comparison. The quotes around*arwill prevent the shell from interpolating the glob. This is a true equality. 这将测试变量$ foo是否等于...
Example 2: Check if strings are not equal in Bash Instead of checking the quality, let’s do the opposite and check the inequality. Bash also provides the negation operator so that you can easily use “if not equal” condition in shell scripts. if [ "$string1" != "Not MyString" ] ...
'Else if'in bash scripting, often written as'elif', is used to check multiple conditions in your code. It is used with the syntax,if [firstStatement]; then... elif [secondCondition]; then... else. It’s a powerful tool that allows your scripts to make decisions based on various scen...
An expression can be: String comparison, Numeric comparison, File operators and Logical operators and it is represented by [expression]: Number Comparisons: -eq - is equal to - if [ "$a" -eq "$b" ] -ne - is not equal to - if [ "$a" -ne "$b" ] -gt - is greater than - ...
To check if the string is NULL or not NULL, use the-zand-nflag. I am using the compact conditional statement syntax to evaluate the condition. $ [[ -z "Howdy" ]] && echo "String is NULL" || echo "String is not NULL" $ [[ -n "Howdy" ]] && echo "String is not NULL" ||...
# Code block executed when condition is false fi Conditions of using if statement Bash provides several conditionals that you can use within if statements: 1. Numeric Comparisons: -eq: Equal to -ne: Not equal to -gt: Greater than -lt: Less than ...
if [[ -z $VAR ]]; then echo "The string is empty." fi 2. Save and run the script: The script states that the string is empty. When the string is not empty, there is no output. To provide an output if the string is not empty, specify theelsecondition in the script, like in...
1) if/then结构: 判断命令列表的退出码是否为0,0为成功。 如果if和then在条件判断的同一行上的话, 必须使用分号来结束if表达式; if和then都是关键字。 关键字(或者命令)如果作为表达式的开头, 并且如果想在同一行上再写一个新的表达式的话, 那么必须使用分号来结束上一句表达式。 if [ condition1 ] then co...
1 if [ condition1 ] 2 then 3 command1 4 command2 5 command3 6 elif [ condition2 ] 7 # Same as else if 8 then 9 command4 10 command5 11 else 12 default-command 13 fi使用if test condition-true这种形式和if[condition-true]这种形式是等价的.向我们前边所说的"["是test的标记.并且以"...
[[ condition1 && condition2 ]] -o和-a操作符一般都是和test命令或者是单中括号结构一起使用的 if [ "exp1"−a"exp1"−a"exp2" ] 操作符 赋值 var=27 注意:在"="之后是不允许出现空白字符,不要混淆= 赋值操作符与 = (有空格)测试操作符 ...