25 июн. 2015 г. · In modern bash (version 4.2 and above): [[ -v name_of_var ]] From help test : -v VAR, True if the shell variable VAR is set.

28 апр. 2020 г. · If you're running under set -u and have a variable that might be unset, and you would need to test whether it's empty with the -z test, ...

16 июн. 2021 г. · In the zsh shell, to test whether a variable is set, beside the standard [ -n "${var+set}" ] , you can also use (( $+var )) , where $+var ...

28 мар. 2023 г. · In Bash in particular, you can use [[ -v var ]] : $ foo=1; unset bar; $ varname=foo $ if [[ -v $varname ]]; then echo set; else echo not set ...

26 нояб. 2012 г. · A different, bash-specific way of testing whether a variable of any type has been defined is to check whether it's listed in ${!PREFIX*} . This ...

27 дек. 2021 г. · The error in your code is that a name reference variable can not be an array, which is what your array1 variable is, which is why you get no as the output from ...

29 янв. 2014 г. · I am looking for a construct in bash, to decide if a variable $WORD is one of defined words. I need something like this:

8 мая 2023 г. · [[ -v "$w" ]] should return True if the shell variable is set (has been assigned a value). But this is returning false. bash.

27 янв. 2018 г. · From help test in bash : -v VAR True if the shell variable VAR is set. True if the shell variable varname is set (has been assigned a value). ...

12 авг. 2021 г. · Here's one way to do it in bash: if declare -p variable >&/dev/null ; then echo "variable exists" else echo "variable does not exist"