Script runs differently from cron

[jmahoney]

Hi

I have a curious problem, can't seem to understand why it happens.

I have a simple script which emails me basic network interface information, I use cron to schedule it hourly.

Here is the crontab entry

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1 * * * * sh -x ~/hourpeep.sh

here is the script

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#!/bin/bash

rm ipcheck.txt
rm iwcheck.txt
rm hourpeep.txt
wget -qO- ipecho.net/plain > ipcheck.txt
echo "  [i]hostname[/i]  " >> ipcheck.txt
ip addr show >> ipcheck.txt
iwcheck wlan0 > iwcheck.txt
cat ipcheck.txt iwcheck.txt > hourpeep.txt
cat hourpeep.txt | msmtp -a default [i]myemail address[/i]

When I run from command line it works fine but when run as a cron job I do not get the iwconfig info - the file iwcheck.txt is empty.

Can someone please explain what is going on here?

Thanks

[SirLagz]

cron doesn't set the path.
You'll need to use the full path when running commands from a script run by cron.
e.g /bin/iwconfig rather than just iwconfig
you can use the command 'which' to find the full path

[rpdom]

Actually, cron does set the path.

What it doesn't do is read .bashrc .profile or any of those files, so any changes to the path set up in there won't take effect - such as including ~/bin

Where is the command "iwcheck"? I can't find any reference to it. If that is a script you have written yourself and put in ~/bin, then that would explain the cron job not being able to find it.

Normally you would get a mail from cron about any error, but I don't think even a local mail client is set up by default in Raspbian. You could try adding " 2> ~/cron.err" on the end of the crontab line, which would list any error messages to that file.

[jmahoney]

@rpdom - yes there is no command iwcheck, sorry that's a typo but only in this post , the script has iwconfig > iwcheck.txt

cron doesn't set the path.
You'll need to use the full path when running commands from a script run by cron.
e.g /bin/iwconfig rather than just iwconfig

If this is the case why does it not also have the same trouble with ip addr show?
I will try adding /bin/ anyway, also added 2>~/con.err, and let you know what happens.

Many thanks
J

[sprinkmeier]

I will try adding /bin/ anyway,

Not everything lives in /bin, use which to find things:

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$ which python
/usr/bin/python

[jmahoney]

Ok, it works now. I used which and changed the relevant line in the script to /sbin/iwconfig wlan0 > iwcheck.txt

Thanks for all your contributions

one question remains though- why do I not need to add /sbin before ip addr show too?

[RaTTuS]

also put temp files in /tmp that way you don't keep writing to your sdcard...

[rpdom]

Ok, it works now. I used which and changed the relevant line in the script to /sbin/iwconfig wlan0 > iwcheck.txt

Thanks for all your contributions

one question remains though- why do I not need to add /sbin before ip addr show too?

The default path for a non-root user is /bin and /usr/bin, ip lives in /bin and that is in your path.

iwconfig is in /sbin, because it can change system settings. The root user's path includes /sbin and /usr/sbin, but as yours doesn't you need to specify it.

[jmahoney]

@RaTTuS- i'm not sure I understand, I thought everything was on the sd card...where are /tmp files stored then?


@rpdom- thanks, that makes sense to me now!

[sprinkmeier]

also put temp files in /tmp that way you don't keep writing to your sdcard...

on my Pi (raspian) /tmp is on the SD card. I usually use /dev/shm

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$ df /tmp/ /dev/shm/
Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/root       15253388 6157948   8320608  43% /
tmpfs              99500       4     99496   1% /run/shm
$ ls -l /dev/shm
lrwxrwxrwx 1 root root 8 May 24 06:17 /dev/shm -> /run/shm

(OK.. so it turns out I'm using /run/shm

[SirLagz]

@rpdom - yes there is no command iwcheck, sorry that's a typo but only in this post , the script has iwconfig > iwcheck.txt

cron doesn't set the path.
You'll need to use the full path when running commands from a script run by cron.
e.g /bin/iwconfig rather than just iwconfig

If this is the case why does it not also have the same trouble with ip addr show?
I will try adding /bin/ anyway, also added 2>~/con.err, and let you know what happens.

Many thanks
J

Sorry. misworded. Other guy explained it much better