Question

I’m quite new to programming. I’m trying to create a script which I’ll run on 3 servers. This script should get the hostname and then run the appropriate command. I guess I should have use ‘cases’ although I’m not sure how.
Here’s my code below.

#!/bin/bash

#Get hostname
hostname="$HOSTNAME"

PATH_DEV="some_path"
PATH_PREPROD="some_path"
PATH_PROD="some_path"

if [ $hostname == "dev" ];
then 

    find $PATH_DEV -name '*.mysql.gz' -type f -mtime +7 -exec rm -rf '{}' \;

elif [ $hostname == "prod" ];

then 

    find $PATH_PROD -name '*.mysql.gz' -type f -mtime +7 -exec rm -rf '{}' \;

elif [ $hostname == "preprod" ];

then

    find $PATH_PREPROD -name '*.mysql.gz' -type f -mtime +7 -exec rm -rf '{}' \;

else 

echo "Unknown hostname!";

fi

It’s only will run on “dev”. For the other 2 cases, it’ll return “Unknown hostname!”
What I’m doing wrong? 🙁

Thanks.

Answer 1

Well, your main question has already been kinda answered in the comments. But as you mentioned that you probably better use case, here is the thing: Your assumption is correct, you definitely should use a case statement instead of the if–elif-construct. One of the advantages will be that matching the host name against patterns will will also solve the problem of fully qualified host names for you. Here is my solution:

#!/bin/bash
PATH_DEV="some_path"
PATH_PREPROD="some_path"
PATH_PROD="some_path"

case "$HOSTNAME" in
  dev|dev.*)
    PATH_TO_USE="$PATH_DEV"
    ;;
  prod|prod.*)
    PATH_TO_USE="$PATH_PROD"
    ;;
  preprod|preprod.*)
    PATH_TO_USE="$PATH_PREPROD"
    ;;
  *)
    echo "Unknown hostname: $HOSTNAME"
    exit 1
    ;;
esac
find "$PATH_TO_USE" -name '*.mysql.gz' -type f -mtime +7 -exec rm -rf '{}' \;

The case statement evaluates the value in $HOSTNAME and checks if it is “dev” or starts with “dev.”, if it is “prod” or starts with “prod.”, if it is “devprod” or starts with “devprod.” respectively. When a match is made, the variable PATH_TO_USE is set to the value of the corresponding PATH_XXX variable. If no specific match is found, the match-always-pattern *) will match and the script terminates with an error message (note that the error message contains the not-matching host name. This safes a lot of work sometimes 😉 ).

If all goes well, the find command is executed at the end. (Another note: try to avoid duplication wherever you can. Doing one find command at the end allows you to change its other parameters in one place.).