请考虑以下Bash函数。 echo "check if variable with name $1 exists"} assert_var "FOO"我们的期望是,应该检测变量FOO,同时也不存在BAR。为此,我需要以某种方式传递变量</em 浏览0提问于2020-07-01得票数 0 回答已采纳 1回答 如何在实践中检查bash语法错误? 、 我需要检查一组脚本在语法上是否正确。我知道...
Rick's Blog bash shell——与if条件相关的参数意义 最近编写脚本,常看到有 if [ -x $variable ] 类的条件语句,不知道相应参数的意义到底是什么, 特摘录如下:fromhttp://blog.csdn.net/aaaaatiger/article/details/1713611 thanks! 1[ -a FILE ] 如果 FILE 存在则为真。2[ -b FILE ] 如果 FILE 存在且...
The pattern will match if it matches any part of the string. Anchor the pattern using the ‘^’ and ‘$’ regular expression operators to force it to match the entire string. The array variable BASH_REMATCH records which parts of the string matched the pattern. The element of BASH_REMATC...
[student@studentvm1 testdir]$ File="TestFile1" ; rm $File ; if [ -s $File ] ; then echo "$File exists and contains data." ; else echo "$File does not exist or is empty." ; fi TestFile1 does not exist or is empty. 现在创建一个空文件用来测试: [student@studentvm1 testdir]...
How to check if a variable exists or is “null”? How to check if a file exists? How to check if a directory exists? How to check if a command succeeds or failed? How to do string comparison and check if a string equals to a value? How to check if a string is in an array?
if else for 循环 while 语句 until 循环 case 语句 break 命令 continue 命令 函数 参考 Bash(GNU Bourne-Again Shell)是一个为GNU计划编写的Unix shell,它是许多Linux平台默认使用的shell。 shell是一个命令解释器,是介于操作系统内核与用户之间的一个绝缘层。准确地说,它也是能力很强的计算机语言,被称为解释性...
- Testifthe specified variable has a [n]on-empty value: [[ -n$variable]] - Testifthe specified variable has an empty value: [[ -z$variable]] - Testifthe specified [f]ile exists: [[ -f path/to/file ]] - Testifthe specified [d]irectory exists: ...
if [[ ${var+x} ]]; then ... # `var' exists (empty or nonempty) if [[ ${1+x} ]]; then ... # Parameter 1 exists (empty or nonempty) The opposite tests if a variable is unset: if [[ ! ${var+x} ]]; then ... # `var' is not set at all if [[ ! ${1+x} ]...
*)# commands to be executed if $variable doesn't match any pattern;;esac 示例: #!/bin/bashday="Monday"case$dayinMonday)echo"Today is Monday.";; Tuesday)echo"Today is Tuesday.";; *)echo"It's some other day.";;esac 在这个示例中,case语句根据变量day的值来决定执行哪个代码块。
Logical operators: The usual suspects && and || work just fine – outside commands – and can be grouped with group commands: if { true || false; } && true; then echo 1; else echo 0; fi. Checking if a variable exists ([[ -v varname ]]): Yes, this is possibly a killer argum...