echo"3. Multiplication"echo-n"Please choose a word [1,2 or 3]? "read operif[$oper-eq1]then echo"Addition Result "$(($inp1+$inp2))elseif[$oper-eq2]then echo"Subtraction Result "$(($inp1-$inp2))elseif[$oper-eq3]then echo"Multiplication Result "$(($inp1*$inp2))elseecho"Inva...
How to check if a string is in an array? How to use the Bash ternary operator? How to negate an if condition in a Bash if statement? (if not command or if not equal) How to use the BASH_REMATCH variable with the Regular Expression Operator =~?
特殊符号(!) 感叹号(reverse (or negate) [bang],[exclamation mark])。 取反一个测试结果或退出状态。 1. 表示反逻辑,比如后面的!=,这个是表示不等于; 2. 表示取反,如:ls a[!0-9] #表示a后面不是紧接一个数字的文件; 3. 在不同的环境里面,感叹号也可以出现在间接变量引用里面; 4. 在命令行中,...
! 感叹号(reverse (or negate) [bang],[exclamation mark])。 取反一个测试结果或退出状态。 1. 表示反逻辑,比如后面的!=,这个是表示不等于; 2. 表示取反,如:ls a[!0-9] #表示a后面不是紧接一个数字的文件; 3. 在不同的环境里面,感叹号也可以出现在间接变量引用里面; 4. 在命令行中,可以用于历史...
To negate the test expression, use the logical NOT (!) operator. When comparing strings , always use single or double quotes to avoid word splitting and globbing issues. Below are some of the most commonly used operators: -n VAR - True if the length of VAR is greater than zero. -z VA...
For example, we want to create a directory Pictures, in case it does not exist, instead of writing the check within an else block, we could just negate our test to see if the file exists, in the following manner:#!/bin/bash DIR="/home/user/scripts" if [ ! -d "$DIR" ]; then...
How can I do an if conditional for a failure of a bash command? Solution 1: Negate the command’s exit status: if ! command ; then echo "Command failed" fi Solution 2: An option to @StephenKitt's accurate response is to employ the "no-op" function from:in the "then" section, al...
Theuntilcommand is identical to thewhilecommand, except that the test is negated; thedolistis executed as long as the last command inlistreturns a non-zero exit status. The exit status of thewhileanduntilcommands is the exit status of the lastdolistcommand executed, or zero if none was ...
The!operator in Bash is used to negate a condition. It is commonly referred to as the “NOT” operator. This operator inverts the exit status of a command or a conditional expression. In simple terms, if a command or expression returns true (exit status 0), the!operator changes it to ...
The until command is identical to the while command, except that the test is negated; list-2 is executed as long as the last command in list-1 returns a non-zero exit status. The exit status of the while and until commands is the exit status of the last command executed in list-2,...