Is there a more consistent way to declare Bash variables and functions?

Question

I am constantly struggling with the decision of how to declare a variable or function in Bash.

Given the following assumptions:

• Bash is the only scripting language available.
• Naming conventions are out of date.

In the case of global variables, I should use:

• foo=bar - inside and outside functions?
• declare -g foo=bar - inside and outside functions?
• local -g foo=bar - inside functions?

In the case of local variables, I should use:

• local foo=bar
• declare foo=bar

In the case of read-only variables, I should use:

• declare -r foo=bar
• local -r foo=bar
• readonly foo - after [1.] or [2.] without the -r flag on the next line.

In the case of functions, I should use:

• foo() { echo bar; }
• foo { echo bar; }
• function foo() { echo bar; }
• function foo { echo bar; }

Answer 1

To forget about this, I define the following at the top of my .bashrc , as well as for each of my Bash shell script files:

 # Allow to define an alias. # shopt -s expand_aliases # Defines a function given a name, empty parentheses and a block of commands enclosed in braces. # # @param name the name of the function. # @param parentheses the empty parentheses. (optional) # @param commands the block of commands enclosed in braces. # @return 0 on success, n != 0 on failure. # alias def=function # Defines a value, ie read-only variable, given options, a name and an assignment of the form =value. # # Viable options: # * -i - defines an integer value. # * -a - defines an array value with integers as keys. # * -A - defines an array value with strings as keys. # # @param options the options. (optional) # @param name the name of the value. # @param assignment the equals sign followed by the value. # @return 0 on success, n != 0 on failure. # alias val="declare -r" # Defines a variable given options, a name and an assignment of the form =value. # # Viable options: # * -i - defines an integer variable. # * -a - defines an array variable with integers as keys. # * -A - defines an array variable with strings as keys. # # @param options the options. (optional) # @param name the name of the variable. # @param assignment the equals sign followed by the value. (optional) # @return 0 on success, n != 0 on failure. # alias var=declare # Declares a function as final, ie read-only, given a name. # # @param name the name of the function. # @return 0 on success, n != 0 on failure. # alias final="readonly -f" 

The above definitions allow me to say, for example:

• def foo { echo bar; } def foo { echo bar; } .
• final foo
• var foo=bar
• val foo=bar

As indicated in the comments, you can mix and match various variable flags, such as var -g foo=bar for the global (-g) variable (var) or val -Ai foobar=([foo]=0 [bar]=1) for read-only (val), associative array (-A), consisting of integer (-i) values.

Implicit redefinition of variables is also implied. Also, the new familiar keywords def , val , var and final should be familiar to any programmer who programs in languages ​​such as JavaScript, Java, Scala, etc.