Help using the terminal.

Question

I'm taking a survey course of languages and we are covering perl this week. I need to write perl script that will parse xml data, but I can't even figure out how to use the terminal.
when I open the terminal I get this line(I subed out my name and username):
firstName-LastName-MacBook-Pro:~ username$
i have tried command from tutorials such as ls and that works, but I can't figure out how to run scripts from a file. I have tried a simple hello world app by typing:
#!/usr/local/bin/perl
print "Hello World!\n";
in text edit saving it as hello.pl then I tried to type hello.pl in the terminal and it says
-bash: first.pl: command not found
can someone explain in simple terms how to run simple programs like this?
thanks, aaron

Answer 1

Thanks for the help. That was a lot of good information. I did have it saved wrong(as rich text).
It is a common mistake, and I'm glad you avoided it.
However I still could not figure out how to run first.pl. using ./first.pl and ~/first.pl
The "chmod +x first.pl" step is need to mark the file as an executable. As previously suggested by etresoft and me, you can also just use "perl first.pl" and avoid the other configuration stuff.
I downloaded fraise as you recommended. Can you guide me through the part were you said, "modify your PATH environment varialble so it includes a directory where you put your personal scripts." i did not understand what you meant by "Create the file .bash_profile in your home directory (you will need ls -a to see the file after you create it). In .bash_profile".
Any file that begins with a period will be invisible to the Finder. And the 'ls' command will by default not show files that begin with a dot. "ls -a" will so all files in a directory, including those that begin with a dot. This was the Unix way of cutting down on clutter in a directory, by having 2 classes of file name, and the ones with a leading dot were then typically used for things like initialization files.
In this case .bash_profile is a bash shell initialization file. By default Mac OS X Terminal sessions use the bash shell to service the commands you enter at the command prompt.
However, a new Mac OS X account typically does NOT have a .bash_profile, so if you wish to customize various bash behaviors you would need to create the .bash_profile yourself.
And as much as I happen to love the vim (and before that vi) text editors, they have a very steep learning curve, so I'm hoping that etresoft was being humorous when he suggested you should avoid a GUI text editor such as Fraise
And besides, if you start down the vi/Vim path, it will only lead to text editor wars with the emacs uses of the world Since you are trying to get through a programming language survey course, perhaps you can skip the text editor debates until a later semester.
With respect to PATH. PATH is a standard Unix environment variable that contains a list of directories that the shell (bash) will search when trying to find the executable file with the same name as the command you entered at the shell command prompt.
If you do not modify your PATH environment variable, it generally looks like:
echo $PATH
/bin:/usr/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin
where each directory is separated by a colon (:). The shell will take the command name you entered, and search each directory from left to right until it find an executable file that matches your command.
What I was suggesting is that you create your own personal directory where you put executable programs and scripts, and then add that personal directory to your PATH environment variable.
Since the bash shell is going to read .bash_profile when you start a new Terminal session and execute the commands it finds in .bash_profile, that is the idea place to customize your PATH
# Assuming you have created a folder called 'bin'
# in your home directory, and you put your personally
# created executable programs and scripts in there
# then the following export command would modify your
# PATH to include your personal bin directory. It does
# not need to be called bin, that is just a long standing
# Unix convention.
export PATH="$PATH:$HOME/bin"
After changing the .bash_profile, you would need to either restart your Terminal session or issue the command
source ~/.bash_profile
I'm a complete beginner when it comes to this stuff.
your help is greatly appreciated.
We all had to start somewhere. In my case the Unix command line prompt was a step up in usability
ps. how to I enclose my code quotes like you did?
Code segments (or anything you do not want the forum software to touch) are enclosed in an identical pair of tags. For example:
... your code snippit here ...
And one final point. etresoft pointed out that the she-bang (#!) line was wrong. I find the following to be the most portable way to specify the #! line
#!/usr/bin/env perl
print "Hello World!
/usr/bin/env is a POSIX standard program that must list in /usr/bin/env, and it will invoke the script interpreter specified as its single argument. /usr/bin/env will use PATH to find the script interpreter, so as long as perl exists in one of the directories specified by PATH, my above #! will always find it, no matter what Unix platform I copy my perl script to, or hand it in for a homework assignment (OK, it is been a lot of years since I did homework, but you might find it useful for your survey course).
etresoft also suggested included the -w option in your #! line. That is not possible when using "#!/usr/bin/env perl", however, you can can just add the "use warnings;" statement to the your perl script and get the same effect:
#!/usr/bin/env perl
use warnings;
print "Hello World!
And if you want perl to look even close at your code you can change warnings to strict
#!/usr/bin/env perl
use strict;
print "Hello World!
{code}
which makes perl really picky about your code.