TestFile1 exists and is empty. [student@studentvm1 testdir]$ File="TestFile1" ; echo "This is $File" > $File ; if [ -s $File ] ; then echo "$File exists and contains data." ; elif [ -e $File ] ; then echo "$File exists and is empty." ; else echo "$File does not ...
逻辑操作符(logical operator)。 在测试结构中,可以用这两个操作符来进行连接两个逻辑值。 ||是当测试条件有一个为真时返回0(真),全假为假; &&是当测试条件两个都为真时返回真(0),有假为假。 43. - 减号 减号,连字符(Hyphen/minus/dash)。 \1. 作为选项,前缀[option, prefix]使用。用于命令或者过滤...
Bash has a large set of logical operators that can be used in conditional expressions. The most basic form of theifcontrol structure tests for a condition and then executes a list of program statements if the condition is true. There are three types of operators: file, numeric, and non-num...
logical AND operator. | | logical OR operator. $# Used to expands the number of arguments passed to the script. $0 Used to expands to the name of the shell. $1, $2 Used as an input parameter that you can add when running script. exit [0-255] Used to exit the script and re...
Using the logical AND operator (&&) When you use the “&&” operator, you're instructing the system to run the second command only if the first command runs successfully. Thus, if the exit code of the first command doesn’t return “0”, then the second command won’t run. Example: ...
pwd [-L|-P] [--help] [--version] pwd [--logical | --physical ] –L或--logical和–P或--physical调用选项与cd命令中的作用相同。 列出目录内容 仅仅在目录之间移动是不够的。最终,您会想要找出这些目录里面有什么。您可以使用ls命令来做到这一点。 以下是ls命令的用法规范——改编自其 man 页面:...
Knowing the exit status of these programs is important when discussing thelogical operators: the AND operator (&&) and the OR operator (||). The AND and OR operators can be used for conditional execution of programs on the command line. Conditional execution occurs when the execution of one ...
Example 4: If statement in bash with logical AND operator This example will show how to combine multiple conditions with a logicalANDcondition. You can also use logicalORconditions in yourIFstatement constructs. LogicalANDin bash code is written with double ampersand&&. Below is an example of lo...
Bash boolean OR operator takes two operands and returns true if any of the operands is true, else it returns false. OR logical operator combines two or more simple or compound conditions and forms a compound condition. Syntax of OR Operator ...
Compact logical expression example Code explanation: It will run the"which neofetch"command and if the return code is zero then whatever comes after&&operator will run. If the return code is above zero (evaluated to false), whatever comes after||operator will run. ...