Starting C

uphu · 01-08-2005, 10:27 PM

Ok, I'm starting to learn C, and I already know a bunch of java and php so its not the language that is confusing me as much as the compiling. I have GCC installed, but I have no idea how to use it. I am also unsure of how to save my files written in C. And no, I have not found any good tutorials written on this. So how would I write a simple hello world program? How do I save it (what extention do I use)? How do I compile it in GCC?

melinda_sayang · 01-08-2005, 10:37 PM

Save it as blabla.c
The in console do this:
$ cd /to/where/the/file/is
$ gcc blabla.c -o blabla
$ ./blabla

Chrax · 01-08-2005, 11:16 PM

Well, assuming you're not using any libraries that need to be linked in, the tags
-o <outfile>
-Wall (all warnings)
-D_GNU_SOURCE (helpful for certain functions, but decreases portability)
are fairly standard. Syntax is the same as most unix programs:

Code:

gcc [FLAGS] infile

If you don't have the -o, it will make the file a.out, which is handy if you don't feel like typing a lot of stuff while you're in debugging phases.

When you get to libraries with special stuff, they'll tell you in the man pages. For example, ncurses requires the -lncurses flag, and GMP requires -lgmp.

reddazz · 01-09-2005, 01:55 AM

I use it slightly differently,

$gcc -o whatever whatever.c

jlliagre · 01-09-2005, 02:00 AM

Or the simpler:

Code:

$ make whatever

(without a makefile, make knows how to build simple executables)

uphu · 01-09-2005, 02:29 PM

Ok, thanks for the help, I got it working. However, I found out that the problem was actually with my Hello World file. For Java, I use the Green Tea Press tutorial to learn, and I found it extremely good. So for C, I decided to learn from the same tutorial converted to C ( http://www.ibiblio.org/obp/thinkCS/cpp/english/ , its C++, but I would expect the print statements to be the same). The hello world file they used was:

Code:

#include <iostream.h>

void main ()
{
  cout << "Hello, world." << endl;
}

This didn't work, it returned a bunch of syntax errors. Then I looked elsewhere and found:

Code:

#include <stdlib.h>

int main(int argc, char **argv) {
     printf("Hello world!\n");
     return 0;
}

This worked fine, and now I am very confused, what is with the first one? How can a language have two completely different print statements?

Also, does anyone have any recommendations for a C or C++ tutorial? I really just need to learn the syntax of it.

jlliagre · 01-09-2005, 03:10 PM

Quote:

How can a language have two completely different print statements?

Not a single language, C and C++ are different languages with differing ways of printing things.
The first version is C++ only, and the second one is regular C.

Hko · 01-09-2005, 03:32 PM

You can compile almost every C-file with a C++ compiler. But not the other way around: compiling C++ code with a C compiler. This is what you have tried.

Pu simply, C++ is like C with extensions. A C-compiler does not recognise these extensions.

BTW the C++ compiler is called "g++".

uphu · 01-09-2005, 03:54 PM

Ok, thanks, I was unaware of this. I thought GCC was a C++ compiler, but I guessed wrong.

could one of you point me in the direction of g++'s main page? Google ignores +'s... :\

Cedrik · 01-09-2005, 04:08 PM

Your first example won't compile with g++ without modify it a little

Code:

#include <iostream>

using namespace std;
int main ()
{
  cout << "Hello, world." << endl;
  return 0;
}

g++ has the same syntax as gcc on command line

Hivemind · 01-09-2005, 04:13 PM

If your C++ tutorial told you that a proper C++ "hello world" program is written as,

Code:

#include <iostream.h>

void main ()
{
  cout << "Hello, world." << endl;
}

I would throw it out the window because it's obsolete crap.

Other posters have shown how it should look in proper C++.

Since you're learning C, I hope you find a good C tutorial and not one of the same quality as your C++ tutorial.

Hko · 01-09-2005, 04:21 PM

Quote:

Originally posted by uphu
Ok, thanks, I was unaware of this. I thought GCC was a C++ compiler, but I guessed wrong.

could one of you point me in the direction of g++'s main page? Google ignores +'s... :\

To make things confusing (

) the software-package/product "GCC" contains compilers for C, C++ and other languages like fortran.

Both the C-compiler "gcc" and the C++-compiler "g++" are part of the "GCC" software package (GCC = GNU Compiler Collection). Its web-site is at
http://gcc.gnu.org/

uphu · 01-09-2005, 05:07 PM

oh, in that case I just need to download the C++ library? I think its on one of my install disks actaully.

Do you happen to know how I can check which libraries I currently have installed for GCC?

itsme86 · 01-09-2005, 05:08 PM

Just so you know, if you enclose C++ in quotes, google won't ignore the +'s (e.g. "C++")

uphu · 01-09-2005, 05:39 PM

Quote:

Originally posted by itsme86
Just so you know, if you enclose C++ in quotes, google won't ignore the +'s (e.g. "C++")

I should've known that >.<

but it still depends