Mac Forum / Programming / Perl / December 2004

directory, I

what happens if you type : perl hw.pl

?

./allan

In a message dated Wed, 22 Dec 2004, Isaac Sherman writes:

The chmod was a necessary but not sufficient step.  Your PATH environment
variable does not contain the current directory (".").  You can fix this
one of two ways:

1. setting PATH to include .:
    setenv PATH $PATH:.
  This can be run as a command and will take effect for the current shell
  only, or you can add it to your .cshrc and it will take effect for all
  future shells.

2. Type "./hw.pl" instead of just "hw.pl".

The second is recommended over the first for security reasons, as if
someone were to insert a command in the current directory you might run it
inadvertently.  It's most especially important that ., if it appears in
PATH, always appear last, so that (for instance) someone couldn't drop a
trojan into the current directory which you pick up by mistake rather than
one of the system commands.

Trey

Try "./hw.pl" (no quotes). Most shells and OSs will NOT let you run
scripts in the working (ie. "where I'm currently located") directory
unless you use a relative path or absolute path. This is to prevent you
from accidentally running scripts due to bad typing, garbage text pasted
erroneously, etc.

Welcome to "Perl".... I think you're going to learn to love this humble
tool. I sure have.

Anyway, type this:

    perl hw.pl

(ie. type in "perl" before the name of your script.

Bill

As others have said, you can run junk.pl using the command

    perl junk.pl

and this will work even if a) the file is not executable and b) there
is no shebang.

You can also execute the script using

    ./junk.pl

but in this case a) the permissions must be modified to make it
executable and b) you must use the shebang (eg #!/usr/bin/perl).  The
sequence below illustrates the procedure.

JD

bash-2.05a$ cd
bash-2.05a$ echo '#!/usr/bin/perl
 print qq~Hello\n~'  > junk.pl
bash-2.05a$ junk.pl
bash: junk.pl: command not found
bash-2.05a$ perl junk.pl
Hello
bash-2.05a$ ./junk.pl
bash: ./junk.pl: /usr/bin/perl: bad interpreter: Permission denied
bash-2.05a$ chmod 755 junk.pl
bash-2.05a$ ./junk.pl
Hello
bash-2.05a$

An excellent start! Always ask Perl for all the help it can give you.

If it didn't, you'd get a different error:

    -bash: ./test.pl: /usr/bin/perl: bad interpreter: No such file or
directory

As you can see, I'm using bash, but the error you'd get from tcsh would
be similar. The point is that the error message isn't just telling you
that *something* couldn't be found, it's also telling you *what* it
couldn't find - /usr/bin/perl. The message you're getting, on the other
hand, is saying it can't find hw.pl - that's a different error.

Of course not - if the permissions were wrong, you'd get a different
error:

    -bash: ./test.pl: Permission denied

That's not the error you got though, so there's no reason to think that
permissions were the problem.

Okay, what's that leave then? Well, let's review what we know: hw.pl
exists and has the correct perms, but the shell can't find it. Well,
where's the shell looking for it? That's listed in the environment
variable PATH. Show the value for PATH with the 'echo' command:

    Sherm-Pendleys-Computer:~ sherm$ echo $PATH
    /sw/bin:/sw/sbin:/bin:/sbin:/usr/bin:/usr/sbin:/usr/X11R6/bin

You'll notice that the current directory '.' is not in my PATH. That
means that, if a script is in the current directory, I can't simply
type its name - I'll get the "command not found" error you've seen.
Instead, I have to tell the shell explicitly where to find it, by
including the full path:

    Sherm-Pendleys-Computer:~ sherm$ test.pl
    -bash: test.pl: command not found
    Sherm-Pendleys-Computer:~ sherm$ ./test.pl
    Howdy, world!

sherm--

Cocoa programming in Perl: http://camelbones.sourceforge.net
Hire me! My resume: http://www.dot-app.org

Isaac, just judging from your problem, it appears that you're probably
a bit new to all things Unix as well (not trying to sound
condescending, just an observation.) I got on OS X for the first time
two years ago and that's about where I was so I can relate to what
you're going through. I had lots of programming experience, had perl
experience (via MacPerl), was a long time user of the classic Mac OS,
and had a faint smattering of Unix know-how, but I kept running into
odd frustrations like what you describe too because I didn't totally
understand the whole Unix thing. Now I do and it's like a whole other
world (well... it is, but anyway.)

My advice--if my assumption is correct--would be to seek out a few Unix
books. I bought a couple of old Unix beginner books from secondhand
stores and they proved to be worth every penny. Even outdated books on
the topic are fine, anything to get your head around the whole concept
of what's going on and how things like perl interact with the command
line and whatnot. I'm still amazed at how powerful it all is and how I
literally could not do my current job without the sort of understanding
that I have now. It pays off in ways you simply cannot imagine.

--Rick Anderson
"The only difference between me and a madman,
is that I am not mad." -- Salvador Dali