How can I execute a bash function using sudo?

Question

I tried exporting the function and then executing it with bash, but that doesn't work:

$ export -f my_func
$ sudo bash -c 'my_func' 
bash: my_func: command not found

If I try to run the function with bash without sudo (bash -c 'my_func'), it works.

Any idea?

Answer 1

Starting from the answer of bmargulies, I wrote a function to cover this issue, which basically realizes his idea.

# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ #
# EXESUDO
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ #
#
# Purpose:
# -------------------------------------------------------------------- #
# Execute a function with sudo
#
# Params:
# -------------------------------------------------------------------- #
# $1:   string: name of the function to be executed with sudo
#
# Usage:
# -------------------------------------------------------------------- #
# exesudo "funcname" followed by any param
#
# -------------------------------------------------------------------- #
# Created 01 September 2012              Last Modified 02 September 2012

function exesudo ()
{
    ### ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ##
    #
    # LOCAL VARIABLES:
    #
    ### ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ##
    
    #
    # I use underscores to remember it's been passed
    local _funcname_="$1"
    
    local params=( "$@" )               ## array containing all params passed here
    local tmpfile="/dev/shm/$RANDOM"    ## temporary file
    local content                       ## content of the temporary file
    local regex                         ## regular expression
    
    
    ### ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ##
    #
    # MAIN CODE:
    #
    ### ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ##
    
    #
    # WORKING ON PARAMS:
    # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    
    #
    # Shift the first param (which is the name of the function)
    unset params[0]              ## remove first element
    # params=( "${params[@]}" )     ## repack array
    
    
    #
    # WORKING ON THE TEMPORARY FILE:
    # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    
    content="#!/bin/bash\n\n"
    
    #
    # Write the params array
    content="${content}params=(\n"
    
    regex="\s+"
    for param in "${params[@]}"
    do
        if [[ "$param" =~ $regex ]]
            then
                content="${content}\t\"${param}\"\n"
            else
                content="${content}\t${param}\n"
        fi
    done
    
    content="$content)\n"
    echo -e "$content" > "$tmpfile"
    
    #
    # Append the function source
    echo "#$( type "$_funcname_" )" >> "$tmpfile"
    
    #
    # Append the call to the function
    echo -e "\n$_funcname_ \"\${params[@]}\"\n" >> "$tmpfile"
    

    #
    # DONE: EXECUTE THE TEMPORARY FILE WITH SUDO
    # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    sudo bash "$tmpfile"
    rm "$tmpfile"
}

Example of usage:
running the following snippet

#!/bin/bash

function exesudo ()
{
    # copy here the previous exesudo function !!!
}

test_it_out ()
{
    local params=( "$@" )
    echo "Hello "$( whoami )"!"
    echo "You passed the following params:"
    printf "%s\n" "${params[@]}" ## print array
}

echo "1. calling without sudo"
test_it_out "first" "second"

echo ""
echo "2. calling with sudo"
exesudo test_it_out -n "john done" -s "done"

exit

Will output

1. calling without sudo
   Hello yourname!
   You passed the following params:
   first
   second
   

2. calling with sudo
   Hello root!
   You passed the following params:
   -n
   john done
   -s
   foo
   

If you need to use this in a shell calling a function which is defined in your bashrc, as asked with a similar question on serverfault by another user, then you have to put the previous exesudo function on the same bashrc file as well, like the following:

function yourfunc ()
{
echo "Hello "$( whoami )"!"
}
export -f yourfunc

function exesudo ()
{
   # copy here
}
export -f exesudo

Then you have to logout and login again or use

source ~/.bashrc

Finally you can use exesudo as follow:

$ yourfunc
Hello yourname!

$ exesudo yourfunc
Hello root!