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I am writing a shell script. In this shell script, I am have a variable that either takes a default value, or the value of an environment variable. However, the environment variable doesn't have to be present.
For instance, assume, before running the script, I perform the following operation:
export DEPLOY_ENV=dev How do I tell the script to search for this environment variable, and store its value in a variable inside the script. Moreover, how do I tell the script that if this environment variable does not exist, store a default variable?
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In the command window that opens, enter echo %VARIABLE%. Replace VARIABLE with the name of the environment variable you set earlier. For example, to check if MARI_CACHE is set, enter echo %MARI_CACHE%. If the variable is set, its value is displayed in the command window.
To display the values of environment variables, use the printenv command. If you specify the Name parameter, the system only prints the value associated with the variable you requested.
To find out if a bash variable is defined: Return true if a bash variable is unset or set to the empty string: if [ -z ${my_variable+x} ]; Also try: [ -z ${my_bash_var+y} ] && echo "\$my_bash_var not defined" Determine if a bash variable is set or not : [[ ! -z ${PURGEIMAGE+z} ]] && echo "Set" || echo "Not defined"
[ -z "${DEPLOY_ENV}" ] checks whether DEPLOY_ENV has length equal to zero. So you could run:
if [[ -z "${DEPLOY_ENV}" ]]; then MY_SCRIPT_VARIABLE="Some default value because DEPLOY_ENV is undefined" else MY_SCRIPT_VARIABLE="${DEPLOY_ENV}" fi # or using a short-hand version [[ -z "${DEPLOY_ENV}" ]] && MyVar='default' || MyVar="${DEPLOY_ENV}" # or even shorter use MyVar="${DEPLOY_ENV:-default_value}" If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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