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Editor: DominicRicottone
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Deletions are marked like this. Additions are marked like this.
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Arguments passed to a function implicitly overwrite the positional variables (`$1`, `$2`, and so on) as well as the argument count variable (`$#`). All of these will be reset to the original values upon the function's return. Arguments passed to a function implicitly overwrite the [[Bash/Variables#Positional_Variables|positional variables]] as well as the [[Bash/Variables#Special_Variables|argument count variable]] (`$#`). All of these will be reset to the original values upon the function's return.
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=== Local Scope ===

To mark a variable as belonging only to a function's scope, declare it with the `local` [[Bash/BuiltinCommands#Local|builtin]].

{{{
local x=y
}}}
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A function does not set the exit code. But it also does not clear the code. The final command in a function effectively sets the error code for the function as well. By default a function does ''not'' set the exit code. But it also does not clear the code. The final command in a function effectively sets the error code for the function as well.
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The `return` builtin causes the function to return immediately. The `return` builtin causes the function to return immediately with a specified exit code.
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{{{
isdirectory() {
  if [ -d "$1" ]; then
    return 0
  else
    return 1
  fi
}

if isdirectory "$some_directory"; then
  :
fi
}}}

Bash Function

Contents

  1. Bash Function
    1. Declaration
    2. Usage
      1. Arguments
      2. Local Scope
      3. Error and Return Codes

Declaration

A function is declared with one of: 

myfunction() {
  :
}

function myfunction() {
  :
}

If the function keyword is used, the parentheses are optional.

Usage

The above functions would be called like: 

myfunction "first argument" "second argument"

Arguments

Arguments passed to a function implicitly overwrite the positional variables as well as the argument count variable ($#). All of these will be reset to the original values upon the function's return.

Note that $0 is not overwritten.

Local Scope

To mark a variable as belonging only to a function's scope, declare it with the local builtin. 

local x=y

Error and Return Codes

By default a function does not set the exit code. But it also does not clear the code. The final command in a function effectively sets the error code for the function as well.

The return builtin causes the function to return immediately with a specified exit code. 

isdirectory() {
  if [ -d "$1" ]; then
    return 0
  else
    return 1
  fi
}

if isdirectory "$some_directory"; then
  :
fi

CategoryRicottone

Bash/Function (last edited 2023-01-29 21:18:51 by DominicRicottone)