More on Awk and Bash scripting

Today we are going to use the power of conditional IF within AWK (aka Conditional AWK programming).

Let's start with an exercise:

You have a file named file2.

#cat /root/file2
22110 2 even
21009 20 even
20903 2 even
24811 2 even
21703 18 even
20811 2 even
22008 2 even
29021 2 even

Where Column1 represents folder name, Column 2 to be used to compute a file name, Column 3 says that Column2 is Even number.

FileName is msg000 appended by (Colum2 -2)/2
e.g
22110 2 even

FileName is msg000 appended by (2-2)/2=0
i.e msg0000.txt


21009 20 even
FileName is msg000 appended by (20-2)/2=9
i.e msg0009.txt

Now we need to write a script, that will remove all those files.

Solution:

Step1: Write awk script that can generate commands to remove those files

#vi cleaner.awk
{
MessageNum=($2-2)/2;

#If MessageNum returns 0 then, there is only one file(may be .txt or wav) so use wildcard to delete that file
if(MessageNum == 0)
print "rm /var/spool/asterisk/voicemail/default/"$1"/INBOX/msg00*";

#If MessageNum returns greater than 0 but less than 10, then delete the bad file with name msg000
else if(MessageNum > 0 && MessageNum < 10)
print "rm /var/spool/asterisk/voicemail/default/"$1"/INBOX/msg000"MessageNum".txt";

#If MessageNum returns greater than 9 but less than 100 , then delete the bad file with name msg00
else if(MessageNum > 9 && MessageNum < 100)
print "rm /var/spool/asterisk/voicemail/default/"$1"/INBOX/msg00"MessageNum".txt";

#If MessageNum returns greater than 99 but less than 1000 , then delete the bad file with name msg0
else if(MessageNum > 99 && MessageNum < 1000)
print "rm /var/spool/asterisk/voicemail/default/"$1"/INBOX/msg0"MessageNum".txt";
}

[Here $1 returns the data on Column1]

Step2:
Run the command
awk -f cleaner.awk /root/file2 > cleanall.sh
This command runs cleaner.awk script for each line of the file file2 and prints the rm command in cleanall.sh file

To execute the script, assign execute permission to the script file.
chmod 700 cleanall.sh

Run the script that contains all the rm commands
./cleanall.sh


For more:

http://www.thegeekstuff.com/2010/02/awk-conditional-statements/
http://www.linuxfocus.org/English/September1999/article103.html