How do I set up cron to run a file just once at a specific time? [closed]

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You really want to use at. It is exactly made for this purpose.

echo /usr/bin/the_command options | at now + 1 day

However if you don’t have at, or your hosting company doesn’t provide access to it, you can have a cron job include code that makes sure it only runs once.

Set up a cron entry with a very specific time:

0 0 2 12 * /home/adm/bin/the_command options

Next /home/adm/bin/the_command needs to either make sure it only runs once.

#! /bin/bash

COMMAND=/home/adm/bin/the_command
DONEYET="${COMMAND}.alreadyrun"

export PATH=/usr/bin:$PATH

if [[ -f $DONEYET ]]; then
  exit 1
fi
touch "$DONEYET"

# Put the command you want to run exactly once here:
echo 'You will only get this once!' | mail -s 'Greetings!' [email protected]

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