Archive for the ‘Scripting’ Category


Script to Batch Random Rename Files

I used this script the other day when I wanted to randomize a group of photos from within my current working directory in the terminal (so my digital photo frame displayed randomly instead of sequentially). You could certainly spend some extra time making this more robust, but it suited my needs. You’ll probably want to modify it a bit to suit yours.

Edit: Thanks to the commenter “thewanderer”, I revisited this script to solve the issue of duplicate $RANDOM values. Now, there’s a recursive function added so files won’t be overwritten!


if [ $# -lt 1 ]; then
   echo "Example Usage: $0 /dev/sdb"
   exit 1


   if [ -f "${rand}.JPG" ]; then
      rename "$i"
      mv "$i" "${rand}.JPG"

echo "This will rename all files randomly in $DIR"
echo -e "Continue?  ( y/n ) : c"
read answer
if [ "$answer" = "n" ] || [ "$answer" = "N" ]
   echo "Exiting..."
   exit 1
   cd $DIR
   for i in *.JPG; do rename "$i"; done
   cd -
) >/dev/null 2>&1 </dev/null

   echo "Files have been renamed with a random number."

Article on Using Python to Send Email

I came across this one while I was trying to figure out a way to script sending an email. I found it to be a very useful and helpful guide and wanted to share, so here it is:

PS. I thought about hitting you with an April Fools joke, but I’ll spare you. 😉 Have a good one today!


Testing Input String for Numeric, Alpha-Numeric, Alpha, or Other POSIX

If you’re trying to scrub your input of a script, a good way to do it is using POSIX along with the tr -d command. This is demonstrated in the shell script below.


# Any of the following can be used, only a few are
# demonstrated:
#[:alnum:]  # Alphanumeric characters
#[:alpha:]  # Alphabetic characters
#[:lower:]  # Lowercase letters
#[:upper:]  # Uppercase letters
#[:digit:]  # Decimal digits
#[:xdigit:] # Hexadecimal digits
#[:punct:]  # Punctuation
#[:blank:]  # Tabs and spaces
#[:space:]  # Whitespace characters
#[:cntrl:]  # Control characters
#[:print:]  # All printable characters
#[:graph:]  # All printable characters except for space
#[a-zA-Z0-9] # Same as [:alnum:]. POSIX can be used.

if [ $# -lt 1 ]; then
   echo "Usage: $0 <text>"


# Check that input is only numeric
if [ -z `echo $text | tr -d "[:digit:]"` ]; then
   echo "Input contains only numeric characters"
   echo "Error: input contains non-numeric characters"

# Check that input is only alpha
if [ -z `echo $text | tr -d "[:alpha:]"` ]; then
   echo "Input contains alpha characters"
   echo "Error: input contains non-alpha characters"

# Check that input is only alphanumeric
if [ -z `echo $text | tr -d "[:alnum:]"` ]; then
   echo "Input contains alphanumeric characters"
   echo "Error: input contains non-alphanumeric characters"

Let’s give it a test run, shall we?

[email protected]$ ./ text
Error: input contains non-numeric characters
Input contains alpha characters
Input contains alphanumeric characters
[email protected]$ ./ text123
Error: input contains non-numeric characters
Error: input contains non-alpha characters
Input contains alphanumeric characters
[email protected]$ ./ 123
Input contains only numeric characters
Error: input contains non-alpha characters
Input contains alphanumeric characters
[email protected]$ 

Set stderr or stdout Redirection for Entire Script

Here’s a quick to to enable standard error (stderr) redirection for an entire script. Just put this command on the top of your script:

exec 2>> stderr.log

Here’s a quick example script to demonstrate:


exec 2>> stderr.log

echo "Hello There! This stdout statement has been redirected to stderr." 1>&2

The output of cat stderr.log:

Hello There! This stdout statement has been redirected to stderr.

The same thing applies for standard out (stdout), except you use “1” instead of “2”:

exec 1>> stderr.log

Here’s a quick example script to demonstrate:


exec 2>> stderr.log

echo "Hello There! This is a stdout statement."

The output of cat stderr.log:

Hello There! This is a stdout statement.

A Nice Color Scheme Tester Script for Terminal Shell

This is a shell script that outputs your current unix color scheme. This is handy for when you’re trying to come up with your own theme. It comes from I’m taking no original credit for this script. I simply want to share it with the readers since I found it very clean and useful. You simply copy the code to a script, use ‘chmod +x’ as usual, and then run it with ./ I’m going to duplicate the script here for redundancy (I want to make sure it’s always there for myself too!):

# Description:
#    Prints a color table of 8bg * 8fg * 2 states (regular/bold)
# Copyright:
#    (C) 2009 Wolfgang Frisch <[email protected]>
# License:
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    GNU General Public License for more details.
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <>.

echo Table for 16-color terminal escape sequences.
echo Replace ESC with \033 in bash.
echo "Background | Foreground colors"
echo "---------------------------------------------------------------------"
for((bg=40;bg<=47;bg++)); do
	for((bold=0;bold<=1;bold++)) do
		echo -en "\033[0m"" ESC[${bg}m   | "
		for((fg=30;fg<=37;fg++)); do
			if [ $bold == "0" ]; then
				echo -en "\033[${bg}m\033[${fg}m [${fg}m  "
				echo -en "\033[${bg}m\033[1;${fg}m [1;${fg}m"
		echo -e "\033[0m"
	echo "--------------------------------------------------------------------- "


Debug Scripts with ‘set -x’

A valuable tool when developing and debugging scripts is set. In particular, the -x or -xtrace options of set will “print a trace of simple commands and their arguments after they are expanded and before they are executed”. Here’s an example of using set -x:


$ cat 

echo "Hello There!"
echo "Here's the date..."
set -x
echo "Also, a calendar..."
echo "Bye!"


$ ./ 
Hello There!
Here's the date...
+ date
Sun Aug  8 21:33:03 MST 2010
+ echo 'Also, a calendar...'
Also, a calendar...
+ cal
    August 2010
Su Mo Tu We Th Fr Sa
 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

+ echo 'Bye!'

Be sure to check out the man page for even more useful options of set.


How To: Add a “Press Any Key to Continue” Message to a Script

Adding a “Press any key to continue” message to a script is actually quite easy because it’s already built into the read command. Here’s a couple examples of how to use it:


echo "A First Method"
read -s -n 1 -p "Press any key to continue..."

# insert echo here for cleaner output

echo "A Second Method"
echo "Press any key to continue..."
read -s -n 1 any_key
echo "Now exiting"
exit 0

Note: “any_key” was simply a made up name. It can be anything. As always, be sure to take a look at the man page for more information!


Run Shell Script Subroutines in Terminal with Source Command

If you run a set of commands frequently, you might want to think about creating a sourced shell script with subroutines. For example, maybe you like to see the current date, a calendar, and a quick fortune (with the fortune package installed). Instead of typing cal and then date and then /usr/games/fortune -s manually each time, simply include it in a shell script that contains a subroutine that will do it all for you. All you need to do is create the script and subroutines and then source it like this:

. /my.subr

Notice the space between the period [.] and the script name. I usually use the .subr extension on my sourced scripts to tell them apart, but you can use whatever filename you want (it doesn’t even have to have an extension).

Then, simply call your subroutine within your shell script. Continuing with the example scenario described above, here is the shell script called my.subr that was sourced…

   /usr/games/fortune -s

   echo "put whatever you want in this function call"
   echo "this is just a filler."

   echo "put whatever you want in this function call"
   echo "this is yet another filler."

This is showing the sourced shell script subroutines in action…

# startday 
     June 2010      
Su Mo Tu We Th Fr Sa
       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         
Fri Jun 11 04:17:56 UTC 2010

Do not drink coffee in early A.M.  It will keep you awake until noon.
# anotherfunction
put whatever you want in this function call
this is just a filler.
# yetanotherfunction
put whatever you want in this function call
this is yet another filler.

Script to Wait for Wireless AP Association During System Startup

The following is a script that could prove to be useful in an embedded Linux environment utilizing a wireless adapter. In order to connect to a wireless network, the wireless adapter needs to associate with an AP which can take some time occasionally. If you’ve edited the /etc/network/interfaces file to automatically obtain an IP address via DHCP, and it doesn’t seem to be getting an IP address during system startup, then this script might be able to help. This script is intended to run on system startup and wait for the access point association. If one is not found, it will eventually timeout.

# Author: Errol E. Burrow II <[email protected]>
# call this script from /etc/rc.local
# this script uses fping which can be installed
# with sudo apt-get install fping

# globals

# turn on extra regex features
shopt -s extglob

until [ $RETRYCOUNT -lt 1 ]; do
	ifconfig wlan0 $MYIP
	iwconfig wlan0 essid $WAPNAME
	# get the access point mac address for wlan0
	ap=$(iwconfig wlan0 | sed "s/Access/~+&/" | tr "~" "n" | grep "+" | cut -c16- | tr -d " ")
	echo "access point mac: [$ap]"
	# check if the ap actually has an expected value
	if [[ $ap =~ [0-9a-f]{2}[:-] ]]; then
		echo "success: connected to wifi access point!"
		route add default gw $GATEWAY
		echo "added default gateway $GATEWAY"
		echo "testing ping to $PINGTESTIP"
		if fping -a -r1 $PINGTESTIP > /dev/null
				echo "success: $PINGTESTIP is alive!"
				echo "warning: $PINGTESTIP cannot be reached!"
		echo "warning: not connected to wifi access point"
		# try again
	echo "retrying connection: $RETRYCOUNT"
	# sleep a bit
	sleep 1

Picup: A Keyword Scanning Script to Synchronize or Upload Photos to an Online Gallery

Picup is a script that scans for photos that match a specified keyword and then uploads it to a gallery on a remote server. Although this script serves a specific purpose to myself, I believe it will be very handy for others to use as well. There is only one dependency: rsync and sh, meaning it will run on just about any UNIX system like Linux or Mac OSX.

Download picup
(Right-Click and “Save Link As…”)

I’ve included two options for getting your photos uploaded to a website: 1.) directly upload the photos that have been found that match the keyword and 2.) synchronize all the photos (even the untagged photos) to a general location on the server and then have the cream of the crop (photos marked with keyword) displayed in another location on the server such as a gallery. The picup script works quite well with photo gallery websites like ZenPhoto where a database is not necessary and photos can be directly uploaded to an album folder such as /public_html/zenphoto/albums/.

There are many other options available as well that can be easily configured. These are all documented in the configuration file called picup_config which is automatically generated and populated with examples when the script is ran for the first time.

Here’s an example run to give you a better idea of what the script actually does:

$ picup 
Searching for pictures marked with "favorites" in:
/MyFiles/Pictures/2010/05 - May/
This might take a while depending on the amount of files in directory...
2010/05 - May/My Pictures in May/IMG_0001.jpg
2010/05 - May/My Pictures in May/IMG_0002.jpg
2010/05 - May/My Pictures in May/IMG_0003.jpg
Please VERIFY the steps that are ABOUT TO BE EXECUTED!
This script is about to synchronize the directory
with the remote site
   [email protected]:/home/username/public_html/pictures
with the options of
   -avzh -e ssh --numeric-ids -i --delete-after --exclude-from=/MyFiles/Pictures/excludes
which will appear on the server as
   /home/username/public_html/pictures/2010/05 - May/My Pictures in May/IMG_0001.jpg
When finished, the following command will ran on the server
   ln -s "/home/username/public_html/pictures/2010/05 - May/My Pictures in May/IMG_0001.jpg" "/home/username/public_html/gallery/albums/2010/05 - May/My Pictures in May/IMG_0001.jpg"

Do you wish to continue? <yes,no> yes
building file list ... done
<rsync output snipped>

Uploading and executing script on server...
server_exec                                   100% 1071     1.1KB/s   00:00    
Finished uploading your pictures.  Enjoy!

I hope you find some use in this script. One of the goals that I was working hard for was to make this as easy as possible to use as well as keep the script speedy in execution. If you have questions, please let me know. I’d like to know if this gets any attention in the ZenPhoto community or elsewhere.

Also, if you’ve seen my old embarrassment of the picup script , I believe this to be a massive improvement.

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