Differences between revisions 2 and 3
⇤ ← Revision 2 as of 2023-01-22 22:48:05 →
Size: 933
Editor: DominicRicottone
Comment:
← Revision 3 as of 2023-01-30 02:01:58 → ⇥
Size: 1179
Editor: DominicRicottone
Comment:
Deletions are marked like this. Additions are marked like this.
Line 37: Line 37:
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 [[Shell/Variables#Positional_Variables|positional variables]] as well as the [[Shell/Variables#Special_Variables|argument count variable]] (`$#`). All of these will be reset to the original values upon the function's return.
Line 45: Line 45:
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.
Line 47: Line 47:
The `return` builtin causes the function to return immediately. 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
}}}

Shell Function

Contents

  1. Shell Function
    1. Declaration
    2. Usage
      1. Arguments
      2. Error and Return Codes

Declaration

A function is declared like: 

myfunction() {
  :
}

A function's name must match [a-zA-Z_][a-zA-Z0-9_]*.

Usage

The above function 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.

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

Shell/Function (last edited 2023-01-30 02:01:58 by DominicRicottone)