initilize the bash input argument when nothing is given

I have a following bash script which is a REST API for a national library using curl command:

#!/bin/bash

for ARGUMENT in "$@"
do
    echo "$ARGUMENT"
     KEY=$(echo $ARGUMENT | cut -f1 -d=)

     KEY_LENGTH=${#KEY}
     VALUE="${ARGUMENT:$KEY_LENGTH 1}"

     export "$KEY"="$VALUE"
done
echo "ARGUMENTS COUNT : " $#
echo "ARGUMENTS LIST  : " $*

out_file_name="newspaper_info_query_${QUERY// /_}.json"
echo ">> Saving DIR: $PWD/$out_file_name"

if [ -z "$ORDER_BY" ]; then ORDER_BY="${ORDER_BY:-}"; fi # returns ERROR when no input is provided!

curl \
-v 'https://digi.kansalliskirjasto.fi/rest/binding-search/search/binding?offset=0&count=10000' \
-o $out_file_name \
-H 'Accept: application/json, text/plain, */*' \
-H 'Cache-Control: no-cache' \
-H 'Connection: keep-alive' \
-H 'Content-Type: application/json' \
-H 'Pragma: no-cache' \
--compressed \
-d @- <<EOF
{   "orderBy":"$ORDER_BY",
    "query":"$QUERY"
}
EOF

Then, I run the aforementioned bash script in python:

import subprocess

def rest_api():
    subprocess.call(['bash', 
                     'my_file.sh',
                     'QUERY=freedom', # mandatory, always provided!
                     'ORDER_BY=RELEVANCE', # optional, if comment: ERROR!
                    ])

if __name__ == '__main__':
    rest_api()

ORDER_BY argument gets the following inputs: RELEVANCE, TITLE_ASC, TITLE_DESC, AUTHOR_ASC, AUTHOR_DESC, DATE, DATE_DESC or simply nothing.

It works when I use either one of those inputs in my python script as the input to the bash script to retrieve a json file with information.

To handle no input case, e.g., initialize ORDER_BY as empty or nothing , I have added if [ -z "$ORDER_BY" ]; then ORDER_BY="${ORDER_BY:-}"; fi to set ORDER_BY with no parameter, e.g., empty! However, It does not work and returns this long error in my saved json out_file_name:

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Is there any better approach to initialize my ORDER_BY argument in bash to get rid of this error for the case no input is provided (initialize empty)?

Cheers,

CodePudding user response：

In your script, you could replace

if [ -z "$ORDER_BY" ]; then ORDER_BY="${ORDER_BY:-}"; fi

with

if [ -z "$ORDER_BY" ]
then
    ORDER_BY=""
else
    ORDER_BY="\"orderBy\":\"$ORDER_BY\","
fi

and replace

"orderBy":"$ORDER_BY",

${ORDER_BY}

That would then pass the ORDER_BY directive in a context based manner and, if not present, would generate the output in the order items are encountered.