Naming convention
This is only a recommendation, it doesn't really set the type of the variable, rather than a best practice to easily recognize variables scope.
| Type | Scope | Convention |
|---|---|---|
| Environment | Global | MY_VARIABLE |
| Global | Global | _MY_VARIABLE |
| Local | Function | my_variable |
Environment variables
Available from anywhere in your code, including sub-processes and background-processes. Environment variables that were declared in a sub-process or a background-process are out of the scope of the main process.
sub-process
#!/bin/usr/env bash
export MAIN_VAR="MAIN_VAR value"
echo "main-process BEFORE - MAIN_VAR = $MAIN_VAR"
# sub-process
bash -c '
export SUB_PROCESS_VAR="SUB_PROCESS_VAR value"
echo "sub-process - SUB_PROCESS_VAR = $SUB_PROCESS_VAR"
echo "sub-process BEFORE - MAIN_VAR = $MAIN_VAR"
export MAIN_VAR="MAIN_VAR changed value"
echo "sub-process AFTER - MAIN_VAR = $MAIN_VAR"
'
echo "main-process AFTER - MAIN_VAR = $MAIN_VAR"
echo "main-process - SUB_PROCESS_VAR = $SUB_PROCESS_VAR"
Output
main-process BEFORE - MAIN_VAR = MAIN_VAR value
sub-process - SUB_PROCESS_VAR = SUB_PROCESS_VAR value
sub-process BEFORE - MAIN_VAR = MAIN_VAR value
sub-process AFTER - MAIN_VAR = MAIN_VAR changed value
main-process AFTER - MAIN_VAR = MAIN_VAR value
main-process - SUB_PROCESS_VAR =
background-process
#!/bin/usr/env bash
export MAIN_VAR="MAIN_VAR value"
echo "main-process BEFORE - MAIN_VAR = $MAIN_VAR"
# background-process
export BG_PROCESS_VAR="BG_PROCESS_VAR value" && \
echo "bg-process - BG_PROCESS_VAR = $BG_PROCESS_VAR" && \
echo "bg-process BEFORE - MAIN_VAR = $MAIN_VAR" && \
export MAIN_VAR="MAIN_VAR changed value" && \
echo "bg-process AFTER - MAIN_VAR = $MAIN_VAR" \
& # set bg process
# Wait for bg processes (jobs) to complete
# Otherwise, the following lines won't be executed
wait
echo "main-process AFTER - MAIN_VAR = $MAIN_VAR"
echo "main-process - BG_PROCESS_VAR = $BG_PROCESS_VAR"
Output
main-process BEFORE - MAIN_VAR = MAIN_VAR value
bg-process - BG_PROCESS_VAR = BG_PROCESS_VAR value
bg-process BEFORE - MAIN_VAR = MAIN_VAR value
bg-process AFTER - MAIN_VAR = MAIN_VAR changed value
main-process AFTER - MAIN_VAR = MAIN_VAR value
main-process - BG_PROCESS_VAR =
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