====== Command Line Hacks ======

===== Image metadata =====
This shows me the EXIF time/date of every image in a directory, useful when I'm sorting:

Needs the debian package 'exif'.
<code bash>
for i in *; do echo $i; exif -t 0x0132 $i  | grep Value; done;
</code>

===== Xargs and Find =====

Performing operations on multiple files using xargs and find:

Escapes the filenames and supplies, through xargs, as many parameters as possible to rm on the command line for efficency. Also an example using two or more parameters with mv.
<code bash>
find $HOME -iname "*.jpg" -print0 | xargs -0 rm
find $HOME -iname "*.jpg" -exec mv {} /dest/dir/ \;
find . -exec grep -Hn hello {} \;
</code>

===== Watch a file =====

Watch a file and do something to it when it changes:

In this case, watch the file 'example.php' and when it changes, show the output in another terminal.
<code bash>
fswatch -0 example.php | xargs -0 -n 1 -I {} php {}
</code>

===== Certificate Expiry =====
Check the expiry date on a SSL certificate PEM file:
<code bash>
openssl x509 -enddate -noout -in cert.pem 
</code>
Read a certificate directly from a URL:
<code bash>
echo | openssl s_client -showcerts -servername glasgow.social -connect glasgow.social:443 2>/dev/null | openssl x509 -inform pem -noout -text

</code>

===== Journalctl =====
I'm so used to using init.d I can't keep these instructions in my head, so they're written here until I remember them.
=== Listing all available services ===
<code bash>systemctl list-unit-files --all | grep enabled</code>
=== Getting logs for a particular service ===
<code bash>journalctl -u sshd</code>