Timer in a loop - Bash

Question

I have a token whos expire in 30 minutes, i want do renew this token until the 30 minutes time expire, i have the following script calling an api:

function token {
        gen_bearer_token=$(curl -X POST "https://api.foo.bar/oauth2/token" -H "accept: application/json" -H "Content-Type: application/x-www-form-urlencoded" -d "client_id=foo&client_secret=bar" | cut -d '{' -f2 | cut -d '}' -f1)
        bearer_token=$(echo $gen_bearer_token | awk '{print $2}' | cut -d '"' -f2 | cut -d '"' -f1)
        token_type=$(echo $gen_bearer_token | awk '{print $6}' | cut -d '"' -f2 | cut -d '"' -f1)
    }

echo -e "HOSTNAME;LAST_SEEN" > ${file}


ids=$(curl -s -X GET 'https://api.foo.bar/devices/queries/devices-scroll/v1?limit=5000' -H  'accept: application/json' -H  'authorization: '${token_type}' '${bearer_token}'' | jq .resources[])
for id in ${ids}
do
    result=$(curl -s -X GET 'https://api.foo.bar/devices/entities/devices/v1?ids='${id}'' -H  'accept: application/json' -H  'authorization: '${token_type}' '${bearer_token}'' | jq '.resources[] | "\(.hostname) \(.last_seen)"')
    if [[ ! -z ${result} ]]
    then
        hostname=$(echo ${result} | awk '{print $1}' | cut -d '"' -f2)
        last_seen=$(echo ${result} | awk '{print $2}' | cut -d '"' -f1)
        echo -e "${hostname};${last_seen}" >> ${file}
    fi
done

in this looping, time duration is more than 2 hours (variable duration) + i want to create a timer to renew token if the times pass through 30 minutes, if passed 30 minutes the request in api will fail.

for id in ${ids}
do
    result=$(curl -s -X GET 'https://api.foo.bar/devices/entities/devices/v1?ids='${id}'' -H  'accept: application/json' -H  'authorization: '${token_type}' '${bearer_token}'' | jq '.resources[] | "\(.hostname) \(.last_seen)"')
    if [[ ! -z ${result} ]]
    then
        hostname=$(echo ${result} | awk '{print $1}' | cut -d '"' -f2)
        last_seen=$(echo ${result} | awk '{print $2}' | cut -d '"' -f1)
        echo -e "${hostname};${last_seen}" >> ${file}
    fi
done

chepner · Accepted Answer · 2021-06-09 18:31:21Z

2

bash as a suitable timer built-in: the SECONDS variable.

Its value is its initial value plus the number of seconds since the most recent assignment. At shell start-up, it is initialized to 0.

All you need to do is check the value of $SECONDS before using the token, and if its value is greater than 1800 (the number of seconds in 30 minutes), get a new one.

SECONDS=1801  # Make sure a token will be generated before the first call
for id in $ids; do
    if [ "$SECONDS" -gt 1800 ]; then
        token
        SECONDS=0
    fi
    ...
done

answered Jun 9, 2021 at 18:31

chepner

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3 Comments

konsolebox Over a year ago

For general use case I suggest adding minisleeps using the external sleep command or the loadable sleep module before the end of the loop to avoid unnecessary CPU use.

chepner Over a year ago

@konsolebox What unnecessary CPU use are you worried about? The value of $SECONDS isn't updated every second; when its value is needed, the shell just computes it from the current time and a timestamp recorded when the variable was last assigned.

konsolebox Over a year ago

I'm talking about the loop itself that would endlessly iterate until SECONDS is updated. Your loop however is finite that's why I said "general use case" where loop is endless. E.g. for (( ;; )); do ...; done or while :; do ...; done. This is for people who'd find your answer and reuse its concept.

bmoreira18 · Accepted Answer · 2021-06-10 22:35:49Z

1

I Solved this problem creating a check response with status code.

response=$(curl -H 'authorization: '${token_type}' '${bearer_token}'' --write-out '%{http_code}' --silent --output /dev/null https://api.foo.bar/devices/entities/devices/v1?ids='0000000000000')

if [ ${response} -eq 200 ]; then
   do something
else
   token
fi

answered Jun 10, 2021 at 22:35

bmoreira18

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