/usr/share/fwbuilder-5.1.0.3599/configlets/sveasoft/shell_functions is in fwbuilder-common 5.1.0-4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 | ## -*- mode: shell-script; -*- 
##
## To be able to make changes to the part of configuration created
## from this configlet you need to copy this file to the directory
## fwbuilder/configlets/sveasoft/ in your home directory and modify it.
## Double "##" comments are removed during processing but single "#"
## comments are be retained and appear in the generated script. Empty
## lines are removed as well.  
##
## Configlets support simple macro language with these constructs:
## {{$var}} is variable expansion
## {{if var}} is conditional operator.
log() {
    echo "$1"
    which "$LOGGER" >/dev/null 2>&1 && $LOGGER -p info "$1"
}
check_file() {
    test -r "$2" || {
        echo "Can not find file $2 referenced by AddressTable object $1"
        exit 1
    }
}
getInterfaceVarName() {
    echo $1 | sed 's/\./_/'
}
getaddr_internal() {
    dev=$1
    name=$2
    af=$3
    L=$($IP $af addr show dev $dev |  sed -n '/inet/{s!.*inet6* !!;s!/.*!!p}')
    test -z "$L" && { 
        eval "$name=''"
        return
    }
    eval "${name}_list=\"$L\"" 
}
##
## This function reads all ipv4 addresses of interface (arg 1) and
## assignes the list to the variable which name is given as arg 2.
##
getaddr() {
    getaddr_internal $1 $2 "-4"
}
##
## This function reads all ipv6 addresses of interface (arg 1) and
## assignes the list to the variable which name is given as arg 2.
##
getaddr6() {
    getaddr_internal $1 $2 "-6"
}
# function getinterfaces is used to process wildcard interfaces
getinterfaces() {
    NAME=$1
    $IP link show | grep ": $NAME" | while read L; do
        OIFS=$IFS
        IFS=" :"
        set $L
        IFS=$OIFS
        echo $2
    done
}
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