Crontab: It's not easy to love you.

Tragic background

Machines running automated scripts cannot connect to the toast server,
You can only write one script on your own and run it every day.
Of course, it should be placed in crontab.
5 3 * * * sh ~/nosecron.sh

Even more tragic results

The next day, I checked the results and fail was mostly used.

Annoying Analysis

Many of them are caused:
catch_pkts.append(pkt.getlayer(IP).build())
AttributeError: ‘NoneType‘ object has no attribute ‘build‘
Then there is a sentence at the beginning of log:
WARNING: Failed to execute tcpdump. Check it is installed and in the PATH
Run tcpdump manually, OK
Manually executed nosecron. Sh, OK
Add the echo $ path to nosecron. SH and put it in crontab. The only difference is:
/Usr/sbin:/usr/bin

Quick Solution

Add
export PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

Clever Solution

In crontab:
5 3 * * * su - root -c "sh /root/nosecron.sh"

Once and for all

Add the following to the front of crontab:
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin
Unfortunately, I don't know why it doesn't take effect.