[Solved] Cron Job Failing

[johnywhy]

My script /usr/local/bin/banana.sh runs just fine, when called directly from command-line.

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#!/bin/bash
notify-send "Banana"

But crontab isn't executing. crontab was created at non-root command-line

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crontab -e
*/1 * * * * banana.sh

This also fails:

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*/1 * * * * /usr/local/bin/banana.sh

task manager shows cron -f is running.

i'm seeing a lot of "Ignored relative path" errors in syslog, but that seems unrelated.

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Aug 20 05:38:18 minty-boost ureadahead[337]: ureadahead:tty: Ignored relative path
Aug 20 05:38:18 minty-boost ureadahead[337]: ureadahead:ttyS21: Ignored relative path
Aug 20 05:38:18 minty-boost ureadahead[337]: ureadahead:: Ignored relative path
Aug 20 05:38:18 minty-boost ureadahead[337]: ureadahead:sys: Ignored relative path
Aug 20 05:38:18 minty-boost ureadahead[337]: ureadahead:devices: Ignored relative path
Aug 20 05:38:18 minty-boost ureadahead[337]: ureadahead:platform: Ignored relative path
Aug 20 05:38:18 minty-boost ureadahead[337]: ureadahead:serial8250: Ignored relative path

[ralplpcr]

Not quite sure I follow the */1 at the front of your statement - are you trying to make it execute every odd minute, or every minute?

I've got 2 possible suggestions. At work now, and can't try it out myself, but I'd think you'd want to include the full path. You *may* also need to tell it to run in bash...... have you verified that your "banana.sh" file has the executable bit set?

Every even minute:

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*/2 * * * * /usr/bin/banana.sh >/dev/null 2>&1

Including the instruction to run with bash:

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*/2 * * * * sh /usr/bin/banana.sh >/dev/null 2>&1

[johnywhy]

as you can see in my script above, i'm not sending output to null. But i just tried that, with all asterisk's, and preceded by sh. Still not firing.

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* * * * * sh /usr/local/bin/banana.sh >/dev/null 2>&1

*/1 * * * * means run every minute.
https://tecadmin.net/crontab-in-linux-w ... -schedule/

* * * * * should also work
https://www.cyberciti.biz/faq/how-to-ru ... linuxunix/

(Technically, */2 doesn't mean "every even minute". It means "every 2nd minute" or "every 2 minutes". */1 means "every 1 minutes")

THX

[gm10]

My script /usr/local/bin/banana.sh runs just fine, when called directly from command-line.

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#!/bin/bash
notify-send "Banana"

But crontab isn't executing. crontab was created at non-root command-line

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crontab -e
*/1 * * * * banana.sh

crontab is executing just fine. But you're forgetting that cron isn't part of your desktop session. It just runs under a minimal environment. To send messages to your desktop it needs to have access to the dbus interface.

Add this as the first command in your script:

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export $(egrep -z DBUS_SESSION_BUS_ADDRESS /proc/$(pgrep -u $LOGNAME mate-session)/environ)

(replace mate-session with whatever desktop session manager you are running)

[MrEen]

Cron doesn't know /usr/local/bin/ by default.

Use /usr/bin/ or /usr/sbin instead.

EDIT: Nevermind. Don't know what I was thinking.

[gm10]

Cron doesn't know /usr/local/bin/ by default.

Use /usr/bin/ or /usr/sbin instead.

EDIT: Nevermind. Don't know what I was thinking.

Why, it's correct except it doesn't know /usr/sbin, either. Best practice is to either always use the full path in crontab or to define PATH at the beginning of your crontab.

[johnywhy]

SCRIPT
DBUS_SESSION_BUS_ADDRESS works! THX gm10.

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#!/bin/bash
export $(egrep -z DBUS_SESSION_BUS_ADDRESS /proc/$(pgrep -u $LOGNAME xfce4-session)/environ)
notify-send "Banana"

you're forgetting that cron isn't part of your desktop session.

ha-ha, i can't forget something i didn't know

Is the DBUS_SESSION_BUS_ADDRESS line needed only if i'm interacting with the desktop?


SH
At command-line, works with or without sh.
But without sh, i get warning. Why?

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$ sh banana.sh
$ banana.sh
/usr/local/bin/banana.sh: line 2: warning: command substitution: ignored null byte in input

CRONTAB
null redirect isn't needed. Works:

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* * * * * /usr/local/bin/banana.sh

DIRECTORY

Don't use these directories. Leave them for package-managed executables.
/usr/bin, /sbin and /bin

If you need the script for all users on your system (but you can also use this for one user), stick it in /usr/local/bin/. One advantage: this directory is already in your PATH so there is no need to edit files.
https://askubuntu.com/a/465162

However, even if i put the script in /usr/local/bin/, i notice that i still must include the full path in the crontab. i would prefer if that wasn't necessary.

THX

[gm10]

Is the DBUS_SESSION_BUS_ADDRESS line needed only if i'm interacting with the desktop?

It's what you need if you want to interact with another process.

Maybe have a look here, although it may just be confusing:
https://en.wikipedia.org/wiki/D-Bus

SH
At command-line, works with or without sh.
But without sh, i get warning. Why?

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$ sh banana.sh
$ banana.sh
/usr/local/bin/banana.sh: line 2: warning: command substitution: ignored null byte in input

ah, sorry, your script references bash, hadn't paid attention. the default shell for cron is sh. for bash modify like this to get rid of the warning:

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export $(egrep -z DBUS_SESSION_BUS_ADDRESS /proc/$(pgrep -u $LOGNAME xfce4-session)/environ | tr \\0 \\n) 

Alternatively remove the #!/bin/bash line from your script or explicitly reference #!/bin/sh instead.

DIRECTORY
[...]
However, even if i put the script in /usr/local/bin/, i notice that i still must include the full path in the crontab. i would prefer if that wasn't necessary.

Run this and add the output (not the command itself) to the top of your user crontab:

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echo PATH=$(printenv PATH)

That way your crontab has access to the same path as you have in a terminal.

[johnywhy]

Is the DBUS_SESSION_BUS_ADDRESS line needed only if i'm interacting with the desktop?

It's what you need if you want to interact with another process.

A desktop process?

default shell for cron is sh

so bash and sh are two different script interpreters?

Run this and add the output (not the command itself) to the top of your user crontab:

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echo PATH=$(printenv PATH)

Neat! However, in this case, it's less effort to just type the path on the command itself
Would be great if crontabs got path globally, without having to type it into every crontab.

THX

[gm10]

Is the DBUS_SESSION_BUS_ADDRESS line needed only if i'm interacting with the desktop?

It's what you need if you want to interact with another process.

A desktop process?

I'm not sure what you mean by that but in case of doubt the answer is "yes, but not limited to". Is notify-send a desktop process?

default shell for cron is sh

so bash and sh are two different script interpreters?

https://en.wikipedia.org/wiki/Unix_shell

Run this and add the output (not the command itself) to the top of your user crontab:

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echo PATH=$(printenv PATH)

Neat! However, in this case, it's less effort to just type the path on the command itself
Would be great if crontabs got path globally, without having to type it into every crontab.

I think you misunderstand. I said to put the PATH into the crontab, not the script. That way it's available for all your cron jobs.

[johnywhy]

I think you misunderstand. I said to put the PATH into the crontab, not the script. That way it's available for all your cron jobs.

I'm to put the output of this into the top of THIS crontab, correct? How will that be seen by other crontabs?

echo PATH=$(printenv PATH)

[gm10]

What other crontabs? Every user only has a single one. And other users have a different PATH so they wouldn't want yours.

[johnywhy]

What other crontabs? Every user only has a single one.

oh, right, ok.

according to the post i linked above, a script for all users can go into /usr/local/bin/

[ralplpcr]

*/1 * * * * means run every minute.
https://tecadmin.net/crontab-in-linux-w ... -schedule/

That's a new one to me - - I've only ever seen it expressed as * * * * * before.
Learn something new every day!