How to determine function name from inside a function

If I have a Bash script like:

#!/bin/bash

f() {
  # echo function name, "f" in this case
}

Is there any way to do this? This could be used in help messages such as

printf "Usage: %s: blah blah blah \n" $(basename $0) >&2; 

Only in this case what I wanted is not $0, which is the file name of the script.

You can use ${FUNCNAME[0]} in bash to get the function name.

From the Bash Reference Manual: > FUNCNAME > > An array variable containing the names of all shell functions currently in the execution call stack. The element with index 0 is the name of any currently-executing shell function. The bottom-most element (the one with the highest index) is "main". This variable exists only when a shell function is executing. Assignments to FUNCNAME have no effect and return an error status. If FUNCNAME is unset, it loses its special properties, even if it is subsequently reset. > > This variable can be used with BASH_LINENO and BASH_SOURCE. Each element of FUNCNAME has corresponding elements in BASH_LINENO and BASH_SOURCE to describe the call stack. For instance, ${FUNCNAME[$i]} was called from the file ${BASH_SOURCE[$i+1]} at line number ${BASH_LINENO[$i]}. The caller builtin displays the current call stack using this information.

When bash arrays are accessed without an index the first element of the array will be returned, so $FUNCNAME will work in simple cases to provide the name of the immediately current function, but it also contains all other functions in the call stack. For example:

# in a file "foobar"
function foo {
    echo foo
    echo "In function $FUNCNAME: FUNCNAME=${FUNCNAME[*]}" >&2
}

function foobar {
    echo "$(foo)bar"
    echo "In function $FUNCNAME: FUNCNAME=${FUNCNAME[*]}" >&2
}

foobar

Will output:

$ bash foobar
In function foo: FUNCNAME=foo foobar main
foobar
In function foobar: FUNCNAME=foobar main

I use ${FUNCNAME[0]} to print current function name

The simplest way to get the function name (from inside a function) is dependent on which shell you are using:

Zsh version

someFunctionName() {
   echo $funcstack[1]
}

Bash version

someFunctionName() {
   echo ${FUNCNAME[0]}
}

Both

someFunctionName() {
  currentShell=$(ps -p $$ | awk "NR==2" | awk '{ print $4 }' | tr -d '-')
  if [[ $currentShell == 'bash' ]]; then
    echo ${FUNCNAME[0]}
  elif [[ $currentShell == 'zsh' ]]; then
    echo $funcstack[1]
  fi
}

A more robust version

columnX () {
    awk "{print \$$1}"
}
rowX () {
	awk "NR==$1"
}

checkShell() {
    ps -p $$ | columnX 4 | rowX 2 | tr -d - 
    # produces bash or zsh (or other shell name like fish)
}

showMethodName(){
    checkShell && echo ${FUNCNAME[0]} || echo $funcstack[1] 
}
showMethodName

Another example:

# in a file "foobar"
foo() {
    echo "$FUNCNAME fuction begins"
}

foobar() {
    echo "$FUNCNAME fuction begins"
}

echo 'begin main'
foo
foobar
echo 'end main'

Will output:

begin main
foo fuction begins
foobar fuction begins
end main