Check for User Nonsense

check-group.sh

#!/bin/bash
for i in $(cut -s -d: -f4 /etc/passwd | sort -u ); do
        if ! grep -q -P "^.*?:x:$i:" /etc/group; then
                echo "Group $i is referenced by /etc/passwd but does not exist in /etc/group"
        fi
done

check-netrc.sh

#!/bin/bash

user_dir="$(
        egrep -v '^(root|halt|sync|shutdown)' /etc/passwd |
        awk -F: '
                ($7 != "/sbin/nologin" && $7 != "/bin/false") {
                        print $1 " " $6
                }
        '
)"

while read user dir; do
        if [[ ! -d "$dir" ]]; then
                echo "Home dir ($dir) of user '$user' does not exist."
                continue
        fi
        if [[ -e "$dir/.netrc" ]]; then
                echo ".netrc file $dir/.netrc exists!"
        fi
done <<< "$user_dir"

check-path.sh

#!/bin/bash

pp="$PATH"
# We need "extended globbing" to use the +(..) and *(..) constructs
shopt -s extglob
if [[ "$pp" =~ :: ]]; then
        echo "Empty Directory in PATH (::)"
        # extglob of +(:) means "one or more ':'"
        # So what we're doing here, is collapsing consecutive colons (1, 2, 3, or even more)
        # into just one colon. And because of the double-slash, this is done for the whole string
        # This removes the diabolical case of ":::" or worse.
        pp="${pp//+(:)/:}"
fi
if [[ "$pp" =~ :$ ]]; then
        echo "Trailing : in PATH"
        # extglob of *(:) means "zero or more ':'"
        # %% means "remove as long as possible from end of string"
        pp="${pp%%*(:)}"
fi

# Replace all ":" with "\n" and consume into array. (One line = one element)
readarray -t p <<< "${pp//:/$'\n'}"

for d in "${p[@]}"; do
        # One or more periods (and none other)
        if [[ "$d" = +(.) ]]; then
                echo "PATH contains . or .. (or variant of)"
                continue
        fi
        if ! [[ -d "$d" ]]; then
                echo "$d is not a directory"
                continue
        fi
        dirperm="$( /usr/bin/stat -c "%A" "$d" )"
        if [[ ${dirperm:5:1} != "-" ]]; then
                echo "Group Write permission set on directory $d"
        fi
        if [[ ${dirperm:8:1} != "-" ]]; then
                echo "Other Write permission set on directory $d"
        fi
        dirown="$( /usr/bin/stat -c "%u" "$d" )"
        if [[ "$dirown" != "0" ]] ; then
                echo "$d is not owned by root"
        fi
        shift
done

shopt -u extglob