Use the if-else statement with the -v option to check if an environment variable is set in bash. The echo command in the if block will be executed if the will
if [ -z ${var+x} ]; then echo "var is unset"; else echo "var is set to '$var'"; fi 参考:https://stackoverflow.com/questions/3601515/how-to-check-if-a-variable-is-set-in-bash 6、换算秒为分钟、小时 代码语言:javascript 代码运行次数:0 运行 AI代码解释 #!/bin/bash a=60100 sw...
当我启动一个shell然后尝试激活一个虚拟环境时，我得到了与这里描述的相同的问题：https://stackoverflow...
- Testifa given variable is [eq]ual/[n]ot [e]qual/[g]reater [t]han/[l]ess [t]han/[g]reater than or [e]qual/[l]ess than or [e]qual to the specified number: [[$variable-eq|ne|gt|lt|ge|leinteger]] - Testifthe specified variable has a [n]on-empty value: [[ -n$vari...
The easiest way to install ShellCheck locally is through your package manager. On systems with Cabal (installs to~/.cabal/bin): cabal update cabal install ShellCheck On systems with Stack (installs to~/.local/bin): stack update stack install ShellCheck ...
The return status (see Section 3.7.5 [Exit Status], page 38) of a simple command is its exit status as provided by the posix 1003.1 waitpid function, or 128+n if the command was terminated by signal n. 一个简单命令的返回状态是由posix 1003.1标准的waitpid函数提供的退出状态,或者是128+n如...
# Set the variable variable="" # Check if the variable is empty if [ -z "$variable" ]; then echo "Variable is empty." else echo "Variable is not empty." fi Copy Save changes and exit from the nanotext editor. Finally,use the chmod command to make the file executableas shown: ...
# set variable identifying the chroot you work in (used in the prompt below) if [ -z "${debian_chroot:-}" ] && [ -r /etc/debian_chroot ]; then debian_chroot=$(cat /etc/debian_chroot) fi # set a fancy prompt (non-color, unless we know we "want" color) ...
#Check the variable is set or not if[-z${Num}];then echo"‘Num’ variable is not set" else echo"‘Num’ variable is set" fi #Assign a value Num=20 #Check the variable is set or not after assigning the value if[-z${Num}];then ...
Using If Then Else to determine if variable is null To evaluate strings, use != and to evaluate numbers use -ne. The following If Then Else statement evaluates whether the $resourceGroup variable has been set. If yes, it returns the value of the variable. If no, it sets the variable....