2 shell questions before the new year

[Jeff Damens]

>   1. What is the difference between
>
>		   sh < file
>   and
>		   sh file

With the "sh file" form, standard input can still be redirected
(that is, standard input for any programs that are invoked by
the shell; obviously the shell takes its input from file); the
"sh < file" form doesn't allow input redirection.

>   2. Why begin a shell script with
>
>		   #!/bin/sh
>   or
>		   #!/bin/csh

This tells the C shell which shell is supposed to interpret the
shell script.  It's necessary because the syntax of shell
commands is different in the two shells; I think /bin/sh is used
by default.  However, if the script starts with a # and doesn't
have the !  construct, the C shell is used

Jeff Damens, Systems Integration Group, Columbia U.

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