Linux – `outputscript | gzip > $file` not overwriting $file

bashcentosgziplinux

I have an hourly cron script which take some output (a mysql dump), pipes it through gzip, and aims to overwrite a file of the same name. When I run it manually as root the file is overwritten. When it is ran by the cron daemon the filename has ".1" appended to it. This keeps happening so that after a while I have lots of files like so:

myfile.gz
myfile.gz.1
myfile.gz.1.1
myfile.gz.1.1.1
myfile.gz.1.1.1.1

and so on.

ps aux|grep crond shows that the daemon is being run as root.

I've tried:

  • renaming the original file, pushing the output, then removing the old file on completion, and
  • deleting the original file before piping the output

but neither works as expected and I just get .1.1.1.1 files.

Script looks like this (nothing special) and is located on a CentOS box in /etc/cron.hourly:

#!/bin/bash
DATE=`date +%H`
DIR="/abs/path/to/dir"
FILE="hourly-${DATE}.gz"
OPTS="..."
mysqldump $OPTS | gzip -9 > $DIR/$FILE

Can anyone advise as to why this simple operation isn't running as expected?

Best Answer

Most likely, your script is written to use Bash features, but it's being run by the Bourne shell. Do you have #!/bin/bash as the first line of your script? Please post it so we can better help you.

Edit:

In scripts that are meant to run as cron jobs, I always specify the full path to programs (such as mysqldump and gzip) since the $PATH variable and things like aliases are going to be different from those in your interactive shell. That way, the results are predictable.

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