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Date: Mon, 7 Jan 2008 10:50:47 -0600
From: Erik Osterholm <freebsd-lists-erik@erikosterholm.org>
To: Steve Franks <stevefranks@ieee.org>
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Cc: User Questions <freebsd-questions@freebsd.org>
Subject: Re: home dir executable (!/bin/sh,
	chmod+x) shell scripts won't run without "sh <script>"
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On Mon, Jan 07, 2008 at 09:13:39AM -0700, Steve Franks wrote:
> > This is a sort of 'don't shoot yourself in the foot' design.  You
> > cannot run a script or binary simply by name if you're cwd is the
> > directory that contains that script or binary.  IIRC, you can't cd /
> > usr/bin and run anything in /usr/bin without explicitly calling that
> > file with the ./ telling the system THIS ONE.
> 
> Ah!  You'd think any one of the many tutorials I read would have
> mentioned that little detail ;)
> 
> Thanks, all
> Steve

You should search your tutorials for the PATH environment variable.

In an over-simplified nutshell, when you type a command in your shell,
it checks a number of different locations for the place to find the
command you're trying to execute.  Some of those locations are every
directory specified in your PATH variable.  My PATH is:
/bin:/usr/bin:/usr/local/bin:/sbin:/usr/sbin

This means that when I type 'ls', the shell looks for an executable
named 'ls' in each of those directories (actually, it probably stops
right after /bin/ls, since that's the correct one.)

If the shell does not find a valid executable in the path, it will say
that there is no such file or directory.  In this case, you would try
specifying the full path by typing /bin/ls, or /home/user/scriptname.
'.' and '..' have special meanings--current directory and
next-directory-up, specifically--so if your current working directory
is /home/user, typing ./scriptname will be largely equivalent to
typing /home/user/scriptname.  ../scriptname would be largely
equivalent to /home/scriptname.  This is why some people suggested
trying ./scriptname in other e-mails in this thread.

The '.' notation for the current working directory enables you to add
the current directory you happen to be in as part of your path (thus
making it searched when executing a command), however this has serious
security implciations, so if you think that it's something you really
want to do, you'll have to find out from someone else how to do it.

erik