UNIX for Dummies Questions & Answers

My crontab file tells cron to run a certain shell script at 10:30 AM every day. The shell script backs up my database with mysqldump and then runs a sed script that does some editing of the backup file.

I have programmed the shell script to write an error message to a file I have in my home directory, ~/errorlog.txt, whenever it can't locate the backups directory. I looked in my errorlog file today and found the following messages:

Code:

Tue Mar  9 10:30:00 EST 2010: Error in mysqldump script: can not find backups directory
Thu Mar 11 10:30:00 EST 2010: Error in mysqldump script: can not find backups directory

Here is the script I used:

Code:

#!/bin/bash

olddir=$PWD;
gotomysql > /dev/null;
# alias
if [ -e backups ]
then
    sudo mysqldump Personal > backups/personal.mysql;
    # Lines 24 through 31 are for editing personal.mysql
    if [ -e ~/Desktop/Computer_Stuff/sed_scripts/edit_backup.sed ]
    then
         sed -f ~/Desktop/Computer_Stuff/sed_scripts/edit_backup.sed backups/personal.mysql > temppersonal.mysql;
        cat temppersonal.mysql > backups/personal.mysql;
        rm temppersonal.mysql;
    else echo "$(date): Error in mysqldump script: can not find edit_backup.sed" >> ~/errorlog.txt;
    fi
else echo "$(date): Error in mysqldump script: can not find backups directory" >> errorlog.txt;
fi
cd $olddir;
unset olddir;

The content of the script is not important. I just put it there so you can see what I'm doing. You can skip over it if you don't want to read my sloppy code.

I think I have determined the problem: cron can only run programs when the computer is on and running. When it's asleep, certain things don't work. Obviously, there is no problem with the script, as it appears to have worked on the 10th. I think this is because I was using my computer at the time.

Do you think I diagnosed the problem correctly? Also, is there any way of working around the fact that I can't have my computer active 24/7?

Don't rely on interpolation or relative references. The cron session env isn't using your usual .profile, etc, so it needs to be handheld...

Instead of "~/", specify the actual $HOME path, etc...

---------- Post updated at 18:11 ---------- Previous update was at 18:11 ----------

Don't rely on interpolation or relative references. The cron session env isn't using your usual .profile, etc, so it needs to be handheld...

Instead of "~/", specify the actual $HOME path, etc...