Shell scripting 101

I had to automate the build system today. The task was simple however my shell scripting knowledge is somewhat limited. I've done itsy-bitsy work on shell scripting but nothing extensive. Today in the process of automating the build I got to learn a few things, might be trivial but they were learning for me.

• To check if the file already exists on the filesystem
  [ -f filename ] && echo"file exists"



• To check if the directory exists on the filesystem
  [ -f dirname ] && echo"dir exists"



• To copy the output of the command executed in the script to a variable.
  result=`pwd`



• export command is used to set a environment variable.



• Use = for comparisons not ==.
  if [ $name = "shiv" ];
then
echo "its me"
fi



• Use option "o" with unzip command to overwrite existing files without prompting.
  unzip -o myArchive.zip
  
  
• Use option "r" to travel recurcively with zip command
  zip -r zipfilename sourcedir *

Following link points to a quick shell scripting reference.
http://www.opengroup.org/onlinepubs/007908799/xcu/shellix.html