awk command has different behaviors when executing the exact same code. Why?

Question

I have created a little shellscript that is capable of receiving a list of values such as "MY_VAR_NAME=var_value MY_VAR_NAME2=value2 ...", separated by spaces only. There should be also the possibility to use values such as MY_VAR_NAME='' or MY_VAR_NAME= (nothing).

These values are then used to change the value inside a environment variables file, for example, MY_VAR_NAME=var_value would make the script change the MY_VAR_NAME value inside the .env file to var_value, without changing anything else about the file.

The env file has the following configuration:

NODE_ENV=development  
APP_PATH=/media  
BASE_URL=http://localhost:3000  
ASSETS_PATH=http://localhost:3000  
USE_CDN=false  
APP_PORT=3000  
WEBPACK_PORT=8080  
IS_CONNECTED_TO_BACKEND=false  
SHOULD_BUILD=false  
USE_REDUX_TOOL=false  
USE_LOG_OUTPUT_AS_JSON=false  
ACCESS_KEY_ID=  
SECRET_ACCESS_KEY=  
BUCKET_NAME=  
BASE_PATH=  
MIX_PANEL_KEY=  
RDSTATION_KEY=  
RESOURCE_KEY=  
SHOULD_ENABLE_INTERCOM=false  
SHOULD_ENABLE_GTM=false  
SHOULD_ENABLE_UTA=false  
SHOULD_ENABLE_WOOTRIC=false

I have debugged my script, and found out that this is the point where sometimes it has a problem

cat .envtemp | awk -v var_value="$VAR_VALUE" \
                    -v var_name="$VAR_NAME" \
                    -F '=' '$0 !~ var_name {print $0} $0 ~ var_name {print $1"="var_value}' | tee .envtemp

This piece of code sometimes outputs to .envtemp the proper result, while sometimes it just outputs nothing, making .envtemp empty

The complete code i am using is the following:

function change_value(){
    VAR_NAME=$1
    VAR_VALUE=$2

    cat .envtemp | awk -v var_value="$VAR_VALUE" \
                    -v var_name="$VAR_NAME" \
                    -F '=' '$0 !~ var_name {print $0} $0 ~ var_name {print $1"="var_value}' | tee .envtemp 

    ls -l -a .env*
}

function manage_env(){
    for VAR in $@
    do
        var_name=`echo $VAR | awk -F '=' '{print $1}'`
        var_value=`echo $VAR | awk -F '=' '{print $2}'`
        change_value $var_name $var_value
    done
}

function main(){
    manage_env $@

    cat .envtemp > .env

    exit 0
}

main $@

Here is an example script for recreating the error. It does not happen every time, and when it happens, it is not always with the same input.

#!/bin/bash
ENV_MANAGER_INPUT="NODE_ENV=production BASE_URL=http://qa.arquivei.com.br ASSETS_PATH=https://d4m6agb781hapn.cloudfront.net USE_CDN=true WEBPACK_PORT= IS_CONNECTED_TO_BACKEND=true ACCESS_KEY_ID= SECRET_ACCESS_KEY= BUCKET_NAME=frontend-assets-dev BASE_PATH=qa"
cp .env.dist .env

#Removes comment lines. The script needs a .envtemp file.
cat .env.dist | grep -v '#' | grep -v '^$' > .envtemp

./jenkins_env_manager.sh ${ENV_MANAGER_INPUT}

Answer 1

Have you tried use two files:

mv .envtemp .envtemp.tmp
cat .envtemp.tmp | awk ... | tee .envtemp