Linux shell Programming

Chapter-1

 concept: (sha-bang ), #! ,The
#! is actually a two-byte
magic number; Immediately followingthe
sha-bang is a    

 pathname.
This is the path to the program that interpretsthe commands in the script. If path name is wrong, will

 generates "Command not found" error message!

 #! can be omitted if the script consists only of a set of generic system commands. If, in fact, the script includes an
extra #! line, then bash will interpret it as a comment

2.1. Invoking the script

  Having written the script, you can invoke it by
shscriptname,
or alternatively bash scriptname. Much more convenient is to makethe script itself directly executable with a
chmod.

chmod +rx scriptname (gives everyone read/execute permission)

chmod u+rx scriptname (gives only thescript owner read/execute permission)

Having made the script executable, you may now test it by./scriptname.
As a final step, after testing and debugging,you would likely want to move it to
/usr/local/bin (asroot, of course), to make the scriptavailable to yourself and all other users as a systemwideexecutable. The script could then be invoked by simply typingscriptname
[ENTER] from thecommand-line.