In programming, it is essential to check if a variable is “set” or “not set,” which means you have to check if a bash script variable has a value or not. This check helps for effective data validation. Howe
在bash命令替换期间,如果变量为空,可以通过以下方式处理: 1. 使用默认值:可以使用`${variable:-default}`的语法,如果变量为空或未设置,则使用默认值。例如,`${var:-...
Afterdeclaring a string variable, use the-zoperator in anif statementto check whether a string is empty or not: MY_STRING="" if [ -z $MYSTRING ] then echo "String is empty" else echo "String is not empty" fi For more Shell scripting tips,check out or Bash/Shell scripting articles!
$ checkarg /home/chris/bin/checkarg: line 10: 1: An argument is required $ checkarg x /home/chris/bin/checkarg: line 10: 2: Two arguments are required $ checkarg '' '' /home/chris/bin/checkarg: line 13: 1: A non-empty argument is required $ checkarg x '' /home/chris/bin/...
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: [[ $variable ...
shift break ;; *) break ;; esac done}parse_user_options "${@}"if ((flag_option_flag)); then echo "flag option set"fiif ((abc_option_flag)); then # Check if the flag options are set or ON: # Logic for when --abc is set. # "${abc_arg}...
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: ...
bash 中的条件语句，基础就是 Test 。 if 先来个实例： x=5; if [ $x = 5 ]; then e...
myArray is NOT empty and contain 3 elements How to check if a Bash Array contains a value? There is no in array operator in bash to check if an array contains a value. Instead, to check if a bash array contains a value you will need to test the values in the array by using a...
Those primaries may be useful if you intend is to check if a variable is empty or not. Though be careful if your shell script runs with the set -u option and your variable does not exist, then your script will fail with an error like bash: myVar: unbound variable....