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i am trying to use following commands in a shell script.. any suggestions to do it a correct way?

[root@testserver ~]# crontab -u oracle -e >> 0 0 * * * /usr/local/scrips/setup.sh crontab: usage error: no arguments permitted after this option Usage: crontab [options] file crontab [options] crontab -n [hostname] Options: -u <user> define user -e edit user's crontab -l list user's crontab -r delete user's crontab -i prompt before deleting -n <host> set host in cluster to run users' crontabs -c get host in cluster to run users' crontabs -s selinux context -x <mask> enable debugging Default operation is replace, per 1003.2
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  • you can write directly to /var/spool/cron/crontabs/<username> it is the file opened with crontab -u afaik Commented Aug 5, 2021 at 9:33
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    @mestia even if this option is supposed to work, it is strongly discouraged (see manpage of crontab) as there's no syntax check performed before installing the crontab which may lead to broken crontabs.... Commented Aug 5, 2021 at 9:35

2 Answers 2

Reset to default
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The -e switch will make crontab interactive, which isn't the wished behaviour.

I suggest you use the crontab -u user file syntax. Below is an example:

root@c:~# crontab -l -u user no crontab for user root@c:~# echo "10 10 * * * /bin/true" >> to_install root@c:~# crontab -u user to_install root@c:~# crontab -l -u user 10 10 * * * /bin/true root@c:~# crontab -l -u user > temp root@c:~# echo "12 12 * * * /bin/false" >> temp root@c:~# crontab -u user temp root@c:~# crontab -l -u user 10 10 * * * /bin/true 12 12 * * * /bin/false
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    Listing the crontab is key, because crontab ... file replaces the entire crontab with the given file’s contents. Commented Aug 5, 2021 at 9:55
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Or in one line :

(sudo crontab -u user -l ; echo "*/5 * * * * /folder/script.sh") | sudo crontab -u user -
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    Watch out: parts before & after the pipe sign will begin execution in parallel, and if the sudo crontab -u user - truncates the user's old crontab before the sudo crontab -u user -l has managed to list it, the old crontab entries will be lost. Commented Aug 5, 2021 at 11:16
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    @telcoM in practice that’s not a problem here, because crontab validates the syntax of the file being installed before installing it — so it accumulates all the content elsewhere, to check it, before it replaces the existing crontab. Commented Aug 5, 2021 at 11:35

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