How to dynamically add daemon & to end of curl

Question

On my first run I need curl to run and wait for response. DB has a trigger that updates a field and I need to wait for that. Then on all my other curls to run on separate threads. I cannot use the parallel options for curl as the version we have does not have it and I cannot update it anyway so I have to go old school and do

for ...
  curl "some curl options" &
end for loop

wait # this waits for all the threads to finish

So I need the "&" sign to be set after the first run. FYI my curl command is 20 lines long and I did try this at the end of the curl command but it doesn't work. Trying single and double quotes around the & sign doesn't work either and give me "unexpected end of file" error.

$(if [[ $firstRun == false ]]; then echo & fi)

The curl command is huge and has many conditionals in it. It would be ugly code and just bad coding practice. — JPM
– JPM, Commented Oct 30, 2023 at 19:24

Gordon Davisson · Accepted Answer · 2023-10-30 17:41:38Z

1

You could write a wrapper function to conditionally run its arguments as a command in the background:

conditionalbg() {
    if [ "$1" = true ]; then
        shift
        # run the passed command in the foreground
        "$@" &
    else
        shift
        # run the passed command in the foreground
        "$@"
    fi
}

...
runinbg=false
for ...
    conditionalbg "$runinbg" curl "some curl options"
    runinbg=true
end for loop

answered Oct 30, 2023 at 17:41

Gordon Davisson

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1 Comment

JPM Over a year ago

This appears to be the best solution for my situation! Logic is reversed but easily fixed. When true then don't daemon it. For all others then add the &. Thank you for the speedy response!

Barmar · Accepted Answer · 2023-10-30 17:17:08Z

0

You can't add syntax to command lines dynamically. So just write two identical commands, one without &.

firstRun=true
for ...; do
    if [[ $firstRun = true ]]
    then 
        curl "some curl options" 
        firstRun=false
    else
        curl "some curl options" &
    fi
done
wait

If you don't want to repeat the whole curl command, put it in a function.

answered Oct 30, 2023 at 17:17

Barmar

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Comments

Ed Morton · Accepted Answer · 2023-10-30 18:18:51Z

0

Put your curl command in a function then call the function with or without & as appropriate:

doCurl() {
    curl "some curl options"
}

doCurl
for ...
  doCurl &
end for loop

wait # this waits for all the threads to finish

answered Oct 30, 2023 at 18:18

Ed Morton

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