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I am learning bash. I accidentally encounter a syntax error with empty function.
#!/bin/bash
# script name : empty_function.sh
function empty_func() {
}
bash empty_function.sh
empty_function.sh: line 3: syntax error near unexpected token `}'
empty_function.sh: line 3: `}'
I suppose it is because of definition of an empty function. I would like to know Why I cannot define an empty function?
277
To find out if a bash variable is empty: Return true if a bash variable is unset or set to the empty string: if [ -z "$var" ]; Another option: [ -z "$var" ] && echo "Empty" Determine if a bash variable is empty: [[ ! -z "$var" ]] && echo "Not empty" || echo "Empty"
$0 Expands to the name of the shell or shell script. This is set at shell initialization. If Bash is invoked with a file of commands (see Section 3.8 [Shell Scripts], page 39), $0 is set to the name of that file.
To declare an empty array, the simplest method is given here. It contains the keyword “declare” following a constant “-a” and the array name. The name of the array is assigned with empty parenthesis.
A "noop" or "null function": var noop = function(){}
Keep the function in the same script where it is used. Write a library of useful functions inside a file and import the file in the script where it is required. A function can be used to perform various operations in a shell script.
A shell function may do neither, either or both. It is generally accepted that in shell scripts they are called functions. A function may return a value in one of four different ways: Change the state of a variable or variables
A procedure, on the other hand, does not return a value, but may produce output. A shell function may do neither, either or both. It is generally accepted that in shell scripts they are called functions. A function may return a value in one of four different ways:
An important thing to note here is that if you declare a variable outside a function, it will behave like a global variable and can be accessed inside a function. 4. Functions that echo output to the standard output.
The bash shell's grammar simply doesn't allow empty functions. A function's grammar is:
name () compound-command [redirection]
function name [()] compound-command [redirection]
And in a compound command of the form:
{ list; }
list can't be empty. The closest you can get is to use a null statement or return:
function empty_func() {
:
}
or
function empty_func() {
return
}
Try this instead:
empty_func() {
:
}
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