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
How do I know if a variable is set in Bash? For example, how do I check if the user gave the first parameter to a function? function a { # if $1 is set ? } The right way if [ -z ${var+x} ]; then echo "var is unset"; else echo "var is set to '$var'"; fi where...
/bin/bash# Set the variablevariable=""# Check if the variable is emptyif[-z"$variable"];thenecho"Variable is empty."elseecho"Variable is not empty."fi Save changes and exit from the nanotext editor. Finally,use the chmod command to make the file executableas shown:...
There are multiple ways to check if a variable is empty or not. Before moving towards those methods, knowing when a variable is called empty is necessary. In
Check file types and compare values. Returns 0ifthe condition evaluates totrue, 1ifit evaluates tofalse. More information: https://www.gnu.org/software/bash/manual/bash.html#index-_005b_005b. - Testifa given variable is equal/not equal to the specified string: ...
Check file types and compare values. Returns 0 if the condition evaluates to true, 1 if it evaluates to false. More information: https://www.gnu.org/software/bash/manual/bash.html#index-_005b_005b. - Test if a given variable is equal/not equal to the specified string: ...
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 复制 #!/bin/bash a=60100 swap_seconds () { SEC=$1...
请考虑以下Bash函数。 echo "check if variable with name $1 exists"} assert_var "FOO"我们的期望是,应该检测变量FOO,同时也不存在BAR。为此,我需 浏览0提问于2020-07-01得票数0 回答已采纳 2回答 以未实例化的变量为条件 我是Bash脚本的新手,对C-type语言有更多的经验。我已经编写了一些带有条件的脚本...
# set variable identifying the chroot you work in (used in the prompt below) if [ -z "${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) ...
How to check if a variable is set in Bash? SettingIFSfor a single statement readarray(akamapfile) issue Tools Match command-line arguments to their help text Bash/Tcsh Comparison Table Collections of scripts Bash One-Liners Awesome Shell ...