sh command

George2 · 09-04-2007, 10:53 PM

Thanks chrism01,

Quote:

Originally Posted by chrism01

The point of specifying the shell your code requires (on production systems) is so that you don't end up with a script that partially runs, then screws up/crashes because it's running under the wrong intepreter.
It's much safer for it not to run at all if it can't find the correct interpreter.
It can cost a company a lot of money if it goes wrong...
It also tells the sysadmin/maintenance prog which shell it will work with, rather than them having to guess.
You might not be avail to be asked when it goes pear-shaped ...

Your practical advice is very helpful.

regards,
George

George2 · 09-04-2007, 11:44 PM

Thanks cfaj,

Quote:

Originally Posted by cfaj

If you are calling a script as the argument to a shell, the shebang makes no difference; it is just another comment. The shebang is only used when the script is executed as a command.

This is an important point. Previously, I think if we add shebang into the 1st line of shell script and at the same time using sh to execute, shell process will be started twice (1st time sh, 2nd time by the shebang line).

regards,
George

George2 · 09-04-2007, 11:46 PM

Thanks for your advice, makyo!

Quote:

Originally Posted by makyo

Hi.

The portability of scripts is decreased if you specify an absolute path.

I once used Solaris often and ran into such problems going back and forth to and from Linux.

I use a perl utility, fixin (fix interpreter), that adjusts the shebang line of scripts for the correct path. It works not only for perl shebangs, but for anything you have in a shebang -- awk, sh, etc.

The fixin program was published in one of the first Programming perl books. An on-line copy of the code is http://search.cpan.org/src/JOHNL/DBD...mples/fixin.pl

Best wishes ... cheers, makyo

PS The origin of the word shebang can be found at http://en.wikipedia.org/wiki/Shebang_%28Unix%29

regards,
George