Bash variables - Explaining their differences - defining the vars outside of a function

01-test_vars_outside_function.sh

#!/usr/bin/env bash

function print_vars(){
  echo "func_declare_g->${declare_g}<-"
  echo "func_declare_x->${declare_x}<-"
  echo "func_declare_only->${declare_only}<-"

  echo "func_export_only->${export_only}<-"

  # echo "func_local_only->${local_only}<-"
  
  echo "func_env_only->${env_only}<-"
  ## the command bellow is to find all environemnts variables defined for all running process
  env env_cmd="output_func_env_cmd" grep -l env_cmd /proc/*/environ
}

declare -g declare_g="output_declare_g"
declare -x declare_x="output_declare_x"
declare    declare_only="output_declare_only"

export     export_only="output_export_only"

## local vars can only be defined inside of a function
# local      local_only="output_local_only"

env        env_only="output_env_only"

print_vars

echo "outside_declare_g->${declare_g}<-"
echo "outside_declare_x->${declare_x}<-"
echo "outside_declare_only->${declare_only}<-"

echo "outside_export_only->${export_only}<-"

# echo "outside_local_only->${local_only}<-"

echo "outside_env_only->${env_only}<-"
## the command bellow is to find all environemnts variables defined for all running process
env env_cmd="output_outside_env_cmd" grep -l env_cmd /proc/*/environ

02-outputs_test_vars_outside_function.txt

## The output of -> env env_only="output_env_only"
HOSTNAME=8756f7b76687
TERM=xterm
declare_x=output_declare_x
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
PWD=/
SHLVL=1
HOME=/root
export_only=output_export_only
_=/usr/bin/env
env_only=output_env_only
##

## Outputs of the echo inside the function print_vars
func_declare_g->output_declare_g<-
func_declare_x->output_declare_x<-
func_declare_only->output_declare_only<-
func_export_only->output_export_only<-
func_env_only-><-
/proc/self/environ
/proc/thread-self/environ
##

## Outputs of the echo outside the function print_vars
outside_declare_g->output_declare_g<-
outside_declare_x->output_declare_x<-
outside_declare_only->output_declare_only<-
outside_export_only->output_export_only<-
outside_env_only-><-
/proc/self/environ
/proc/thread-self/environ
##

## Check the link below to understand the two /proc/* files
## See on Medium: https://medium.com/unboxing-the-cloud/bash-variables-things-that-you-probably-dont-know-about-it-8a5470887331?sk=26693ca772a0c54c99d3712303560ed4
## See on my Website: https://www.lozanomatheus.com/post/bash-variables-things-that-you-probably-don-t-know-about-it