why assign python command to sh var? what does this file do? [closed]-CodePudding

anyone knows what this last line does in this .sh file?
why assign var to itself with python command?

how python file (bigquery library) has access to json file name?

DAY=2021-01-01
GOOGLE_APPLICATION_CREDENTIALS=file.json
GOOGLE_APPLICATION_CREDENTIALS=$GOOGLE_APPLICATION_CREDENTIALS python3 run_calc_bq.py table_name $DAY $DAY

Thank you :)

CodePudding user response：

It's setting the value of GOOGLE_APPLICATION_CREDENTIALS in the environment of the Python command, but not in the shell itself. Repeating the variable name is a bit odd. If you were fine with adding the variable to the environment for all commands, you could write

DAY=2021-01-01
export GOOGLE_APPLICATION_CREDENTIALS=file.json
python3 run_calc_bq.py table_name "$DAY" "$DAY"

If you really do want it in just the Python command's environment, you could use a much shorter variable name.

DAY=2021-01-01
x=file.json
GOOGLE_APPLICATION_CREDENTIALS=$x python3 run_calc_bq.py table_name "$DAY" "$DAY"

CodePudding user response：

The variable GOOGLE_APPLICATION_CREDENTIALS is declared in the parent script, but it is not exported.

In order to make it available to the child script, you have two options:

Export it

# export to all child processes
export GOOGLE_APPLICATION_CREDENTIALS

Or prepend it to the command line

# export to this specific command
GOOGLE_APPLICATION_CREDENTIALS=$GOOGLE_APPLICATION_CREDENTIALS python3 ...