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@sj26
Last active March 8, 2024 18:31
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Bash retry function

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# Retry a command up to a specific numer of times until it exits successfully,
# with exponential back off.
#
# $ retry 5 echo Hello
# Hello
#
# $ retry 5 false
# Retry 1/5 exited 1, retrying in 1 seconds...
# Retry 2/5 exited 1, retrying in 2 seconds...
# Retry 3/5 exited 1, retrying in 4 seconds...
# Retry 4/5 exited 1, retrying in 8 seconds...
# Retry 5/5 exited 1, no more retries left.
#
function retry {
local retries=$1
shift
local count=0
until "$@"; do
exit=$?
wait=$((2 ** $count))
count=$(($count + 1))
if [ $count -lt $retries ]; then
echo "Retry $count/$retries exited $exit, retrying in $wait seconds..."
sleep $wait
else
echo "Retry $count/$retries exited $exit, no more retries left."
return $exit
fi
done
return 0
}
@jakub-bochenski
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@hcharley just define the function in your .bashrc or whatnot and you will be able to call it directly

@albertvaka
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What's the license of this code?

@sj26
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sj26 commented Sep 5, 2022

It didn't have one, but I'm happy to pop it under MIT, and have added a license file.

@cmedved
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cmedved commented Dec 8, 2022

Personally, I much preferred it without a license, because now I can't use it without copying that chunk of text into my script above the function... which is a bit excessive.

@sj26
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sj26 commented Dec 8, 2022

Fair point, I don't really care about the license notice being preserved. Unlicensed.

@ypid
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ypid commented Dec 12, 2022

https://reuse.software/ comes to the rescue. You can drop that license file (at least for this small script probably the easiest) or let the reuse tool manage it. Than add something like this to the top of the file:

# SPDX-FileCopyrightText: 2016, 2018-2019 Jane Doe <jane@example.com>
#
# SPDX-License-Identifier: GPL-3.0-or-later

@corneliusroot
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Excellent function. Used it in a watchdog script, helps avoid false alarms due to initial time-outs. Thanks for publishing this!

@domo141
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domo141 commented Dec 30, 2022

Perhaps localize $wait and $exit, too ?

@grugnog
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grugnog commented Sep 3, 2023

One improvement would be to log to stderr instead of stdout - e.g.:
echo "Retry $count/$retries exited $exit, retrying in $wait seconds..." >&2

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