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🦑📜 How to save the configuration in a shell script :

1) Save the configuration while the shell script is running using a simple yet effective method.
Shell script

2) I'll use the following shell script to illustrate the idea.

Nothing fancy, it will display the available disk space on a specific server and partition.

#! / usr / bin / env bash
# Display available disk space on specific server and partition

# default parameters
default_bastion = ""
default_busername = ""
default_server = "localhost"
default_username = "milosz"
default_partition = "/ srv"

# nextcloud server
nextcloud_server = "nextcloud.local"
nextcloud_partition = "/ data"

# dokuwiki server
dokuwiki_bastion = "bastion.example.org"
dokuwiki_busername = "bouncer"
1dokuwiki_server = "192.0.2.10"
dokuwiki_username = "dokuwiki"
dokuwiki_partition = "/ wiki"

# kolab server
kolab_bastion = "bastion.example.org"
kolab_busername = "bouncer"
kolab_server = "192.0.2.20"
kolab_username = "monitoring"
kolab_partition = "/"

# get defined servers / applications
applications = "$ ((set -o posix; set) | awk -F '=' '/ _server / {split ($ 1, array," _ "); print array [1]}' | grep -v default)"

# get defined attributes
attributes = "$ ((set -o posix; set) | awk -F '=' '/ default_ / {split ($ 1, array," _ "); print array [2]}')"

3) for application in $ applications; do
# define attributes for server / application
for attribute in $ attributes; do
application_attribute = "$ {application} _ $ {attribute}"
default_attribute = "default _ $ {attribute}"
if [-n "$ {! application_attribute}"]; then
eval "$ {attribute}" = "$ {! application_attribute}"
else
eval "$ {attribute}" = "$ {! default_attribute}"
fi
done

# perform an action
if [-n "$ bastion"]; then
bastion_param = "- J $ {busername} @ $ {bastion}"
else
bastion_param = ""
fi
echo -n "$ server:"
ssh $ bastion_param $ server -l $ username "bash -c 'df -h --output = avail $ partition | sed 1d'"
done
Using
Run the above shell script to see the available disk space on the specified servers.

nextcloud.local: 87G
192.0.2.10: 98G
192.0.2.20: 5.5G
How it works
Attributes

4) Define default values, remember to include blanks.

# default parameters
default_bastion = ""
default_busername = ""
default_server = "localhost"
default_username = "milosz"
default_partition = "/ srv"

5) These variables will be used to retrieve the attribute names.
# get defined attributes
attributes = "$ ((set -o posix; set) | awk -F '=' '/ default_ / {split ($ 1, array," _ "); print array [2]}')"
The extracted attribute names.

attributes = "bastion busername server username partition"
Applications
Define the attributes for each application.

# nextcloud server
nextcloud_server = "nextcloud.local"
nextcloud_partition = "/ data"
[...]

6) These variables will be used to retrieve the application names.

Note that I am using the server attribute as the app indicator in this example.
# get defined servers / applications
applications = "$ ((set -o posix; set) | awk -F '=' '/ _server / {split ($ 1, array," _ "); print array [1]}' | grep -v default)"

7) The names of the extracted applications.

applications = "nextcloud dokuwiki kolab"
Parsing attributes for each application
I will iterate over the list of applications.

8) for application in $ applications; do
Assign attributes (for example, server, username ...) using the application_attribute variable (values such as nextcloud_server, nextcloud_username,… depending on the application name) to define the target variable name and read value using the $ {! Application_attribute}. Use the default if empty.

# define attributes for server / application
for attribute in $ attributes; do
application_attribute = "$ {application} _ $ {attribute}"
default_attribute = "default _ $ {attribute}"
if [-n "$ {! application_attribute}"]; then
eval "$ {attribute}" = "$ {! application_attribute}"
else
eval "$ {attribute}" = "$ {! default_attribute}"
fi
done

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