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: http://docs.python.org/library/email-examples.html.
PS. I thought about hitting you with an April Fools joke, but I’ll spare you. 
Have a good one today!
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.
#!/bin/sh # 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>" exit fi text=$1 # Check that input is only numeric if [ -z `echo $text | tr -d "[:digit:]"` ]; then echo "Input contains only numeric characters" else echo "Error: input contains non-numeric characters" fi # Check that input is only alpha if [ -z `echo $text | tr -d "[:alpha:]"` ]; then echo "Input contains alpha characters" else echo "Error: input contains non-alpha characters" fi # Check that input is only alphanumeric if [ -z `echo $text | tr -d "[:alnum:]"` ]; then echo "Input contains alphanumeric characters" else echo "Error: input contains non-alphanumeric characters" fi
Let’s give it a test run, shall we?
user@localhost$ ./input.sh text Error: input contains non-numeric characters Input contains alpha characters Input contains alphanumeric characters user@localhost$ ./input.sh text123 Error: input contains non-numeric characters Error: input contains non-alpha characters Input contains alphanumeric characters user@localhost$ ./input.sh 123 Input contains only numeric characters Error: input contains non-alpha characters Input contains alphanumeric characters user@localhost$
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:
#!/bin/sh 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:
#!/bin/sh 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.
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 http://www.frexx.de/xterm-256-notes/. 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 colortheme.sh’ as usual, and then run it with ./colorscheme.sh. I’m going to duplicate the script here for redundancy (I want to make sure it’s always there for myself too!):
#!/bin/bash # # 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 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # 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 <http://www.gnu.org/licenses/>. echo echo Table for 16-color terminal escape sequences. echo Replace ESC with \033 in bash. echo 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 " else echo -en "\033[${bg}m\033[1;${fg}m [1;${fg}m" fi done echo -e "\033[0m" done echo "--------------------------------------------------------------------- " done echo echo
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:
Script
$ cat setx.sh #!/bin/sh echo "Hello There!" echo "Here's the date..." set -x date echo "Also, a calendar..." cal echo "Bye!" $
Execution
$ ./setx.sh
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!'
Bye!
$
Be sure to check out the man page for even more useful options of set.
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:
#!/bin/sh echo "A First Method" read -s -n 1 -p "Press any key to continue..." # insert echo here for cleaner output echo 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!
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…
startmyday(){
cal
date
echo
/usr/games/fortune -s
}
anotherfunction(){
echo "put whatever you want in this function call"
echo "this is just a filler."
}
yetanotherfunction(){
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.
#
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.
#!/bin/bash # # CONNECT TO WIRELESS NETWORK # 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 MYIP="192.168.0.121" WAPNAME="SSVR3" GATEWAY="192.168.0.141" PINGTESTIP="10.10.10.1" RETRYCOUNT=10 # 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 then echo "success: $PINGTESTIP is alive!" break else echo "warning: $PINGTESTIP cannot be reached!" fi else echo "warning: not connected to wifi access point" # try again fi echo "retrying connection: $RETRYCOUNT" let RETRYCOUNT-=1 # sleep a bit sleep 1 done
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 /MyFiles/Pictures/ 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.
If you find yourself needing to echo out multiple lines to the console, or even to another file, then you’ll want to use the following method which is much cleaner and much more efficient. It’s very useful in creating another document, script, or file without having to use echo for each line.
#!/bin/sh cat > new_file << EOF This will be line one This will be line two This will be line three This will be line four indented Notice the absence of spaces on the next line EOF cat new_file
Basically, what the above script will do is use cat to write the following lines up to a delimiter, in this case EOF, to a file called new_file. The most important thing to keep in mind is that for this to work, there cannot be any spaces before the delimiter. The output of running this script looks like:
This will be line one This will be line two This will be line three This will be line four indented Notice the absence of spaces on the next line
Naturally, this method will also work in the terminal command line and is not restricted to only shell scripts.