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Using the same variable across multiple scripts

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2

What is the best practice for using the same bash variable (that is NOT an environment variable) across multiple scripts which call each other sequentially? Should this variable be defined in every script or function in order to keep them atomically reusable?

For example, let's say that I have one script which sources a functions.sh script with many smaller reusable functions.

#script_1

DIR="$( cd "$( dirname "$BASH_SOURCE[0]" )" && pwd )"

country="$1"

. $DIR/functions.sh

function_1
function_2 $country

#functions.sh

DIR="$( cd "$( dirname "$BASH_SOURCE[0]" )" && pwd )"

function_1() 
echo "The country is $country"


function_2()
local country="$1"

if [[ $country^^ == "UK" ]]; then
 echo "Fish and Chips"
else
 echo "Try local food"
fi

My question is: should the $country variable be defined locally in each atomic function in the functions.sh source file?

When those functions are called, $country is already defined in the initial script, so I wouldn't have to pass it on as a parameter. I'm thinking that each of those scripts should not depend on some variable maybe being defined previously, but they should be given all the information they require via parameters, so that they can be reused easily.

Also, should it be defined as country or COUNTRY?

bash shell

share|improve this question

edited Mar 21 at 14:44

Vlad-Octavian

asked Mar 21 at 9:55

Vlad-OctavianVlad-Octavian

112

New contributor

Vlad-Octavian is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  This is the same as using global variables in any other language. You should try to avoid them, parameters are generally better.
  
  – Barmar
  Mar 21 at 9:57
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  All-uppercase variables are conventionally reserved for environment variables.
  
  – Barmar
  Mar 21 at 9:58
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @Barmar so to sum up, you are saying: keep the variable in lowercase (since it's not an environment variable) and it's best to define and pass the variable as a parameter in each function instead of relying on it already existing in the context in which the script is run.
  
  – Vlad-Octavian
  Mar 21 at 11:51
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  I'd go further and tell you not to use ALLCAPS_VARS at all. It's too easy to use PATH=/path/to/file; DIR=$(dirname "$PATH") and then you wonder why your script suddenly emits "dirname: not found"
  
  – glenn jackman
  Mar 21 at 12:25
  
  

  
  
  
  

add a comment | 

2

What is the best practice for using the same bash variable (that is NOT an environment variable) across multiple scripts which call each other sequentially? Should this variable be defined in every script or function in order to keep them atomically reusable?

For example, let's say that I have one script which sources a functions.sh script with many smaller reusable functions.

#script_1

DIR="$( cd "$( dirname "$BASH_SOURCE[0]" )" && pwd )"

country="$1"

. $DIR/functions.sh

function_1
function_2 $country

#functions.sh

DIR="$( cd "$( dirname "$BASH_SOURCE[0]" )" && pwd )"

function_1() 
echo "The country is $country"


function_2()
local country="$1"

if [[ $country^^ == "UK" ]]; then
 echo "Fish and Chips"
else
 echo "Try local food"
fi

My question is: should the $country variable be defined locally in each atomic function in the functions.sh source file?

When those functions are called, $country is already defined in the initial script, so I wouldn't have to pass it on as a parameter. I'm thinking that each of those scripts should not depend on some variable maybe being defined previously, but they should be given all the information they require via parameters, so that they can be reused easily.

Also, should it be defined as country or COUNTRY?

bash shell

share|improve this question

edited Mar 21 at 14:44

Vlad-Octavian

asked Mar 21 at 9:55

Vlad-OctavianVlad-Octavian

112

New contributor

Vlad-Octavian is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  This is the same as using global variables in any other language. You should try to avoid them, parameters are generally better.
  
  – Barmar
  Mar 21 at 9:57
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  All-uppercase variables are conventionally reserved for environment variables.
  
  – Barmar
  Mar 21 at 9:58
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @Barmar so to sum up, you are saying: keep the variable in lowercase (since it's not an environment variable) and it's best to define and pass the variable as a parameter in each function instead of relying on it already existing in the context in which the script is run.
  
  – Vlad-Octavian
  Mar 21 at 11:51
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  I'd go further and tell you not to use ALLCAPS_VARS at all. It's too easy to use PATH=/path/to/file; DIR=$(dirname "$PATH") and then you wonder why your script suddenly emits "dirname: not found"
  
  – glenn jackman
  Mar 21 at 12:25
  
  

  
  
  
  

add a comment | 

What is the best practice for using the same bash variable (that is NOT an environment variable) across multiple scripts which call each other sequentially? Should this variable be defined in every script or function in order to keep them atomically reusable?

For example, let's say that I have one script which sources a functions.sh script with many smaller reusable functions.

#script_1

DIR="$( cd "$( dirname "$BASH_SOURCE[0]" )" && pwd )"

country="$1"

. $DIR/functions.sh

function_1
function_2 $country

#functions.sh

DIR="$( cd "$( dirname "$BASH_SOURCE[0]" )" && pwd )"

function_1() 
echo "The country is $country"


function_2()
local country="$1"

if [[ $country^^ == "UK" ]]; then
 echo "Fish and Chips"
else
 echo "Try local food"
fi

My question is: should the $country variable be defined locally in each atomic function in the functions.sh source file?

When those functions are called, $country is already defined in the initial script, so I wouldn't have to pass it on as a parameter. I'm thinking that each of those scripts should not depend on some variable maybe being defined previously, but they should be given all the information they require via parameters, so that they can be reused easily.

Also, should it be defined as country or COUNTRY?

bash shell

share|improve this question

edited Mar 21 at 14:44

Vlad-Octavian

asked Mar 21 at 9:55

Vlad-OctavianVlad-Octavian

112

New contributor

Vlad-Octavian is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

#script_1

DIR="$( cd "$( dirname "$BASH_SOURCE[0]" )" && pwd )"

country="$1"

. $DIR/functions.sh

function_1
function_2 $country

#functions.sh

DIR="$( cd "$( dirname "$BASH_SOURCE[0]" )" && pwd )"

function_1() 
echo "The country is $country"


function_2()
local country="$1"

if [[ $country^^ == "UK" ]]; then
 echo "Fish and Chips"
else
 echo "Try local food"
fi

share|improve this question

edited Mar 21 at 14:44

Vlad-Octavian

asked Mar 21 at 9:55

Vlad-OctavianVlad-Octavian

112

New contributor

Vlad-Octavian is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this question

edited Mar 21 at 14:44

Vlad-Octavian

asked Mar 21 at 9:55

Vlad-OctavianVlad-Octavian

112

New contributor

Vlad-Octavian is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked Mar 21 at 9:55

Vlad-OctavianVlad-Octavian

112

New contributor

Vlad-Octavian is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked Mar 21 at 9:55

Vlad-OctavianVlad-Octavian

112