====== Shelltricks ======

Miscellaneous small shell scripts that I may or may not need again in the far future.


===== Check umask for all users =====

<code bash check_user_umasks.sh>
#!/bin/bash

for user in $(awk -F: '{print $1}' /etc/passwd); do
    printf "%-20s" "$user" ; su -s /bin/bash -c 'umask' -l $user 2>/dev/null
done
</code>

Original source: https://unix.stackexchange.com/a/82645


===== Show the dates of the oldest unseen messages in multiple maildirs, newest first =====

Beware of weird directory names. I am not responsible if this somehow does an ''rm -rf --no-preserve-root /'' or something.

<code bash>
for dir in /var/vmail/domain/*/Maildir/new /var/vmail/domain/*/Maildir/.*/new; do
    echo -e "$(stat -c %y $dir/$(ls -Art $dir | head -1))\t$dir"
done | grep -v '/\./' | sort -rn
</code>

Same thing, but for the newest seen messages:

<code bash>
for dir in /var/vmail/domain/*/Maildir/cur /var/vmail/domain/*/Maildir/.*/cur; do
    echo -e "$(stat -c %y $dir/$(ls -At $dir | head -1))\t$dir"
done | grep -v '/\./' | sort -rn
</code>

The only differences are the folders (''cur'' vs. ''new'') and the sorting done by ''ls''.


===== Extract IP addresses from "ip a" output by regex =====

Might be useful for scripting, I guess.

<code bash>
IPRE='192\.168\.1\.|2001:1234:'
ip a s up | grep -Eo "inet6? [^ /]+" | cut -d' ' -f2 | grep -E "$IPRE"
</code>

This prints:

<code>
192.168.1.123
2001:1234:5678:90ab:cdef:1234:5678:90ab
</code>