Hello World compiling problem

[JoFrRi]

Hi. I'm new to Ubuntu and C programming. I have written the first example program that prints "Hello World" as the following:


#include <stdio.h>

int main()
{
printf("Hello World\n");
return 0;
}

The file is saved as test.c. I have tried the following commands:


gcc test.c -otest

and I get the following error:


/usr/lib/gcc/i486-linux-gnu/4.3.2/../../../../lib/crt1.o: In function `_start':
(.text+0x18): undefined reference to `main'
collect2: ld returned 1 exit status

I have installed the build-essential package already.

Any help, much appreciated.

[Shwefty]

I'm relatively fresh on C programming too, but I always used the command:

gcc test.c - lm
a.out

[JoFrRi]

I'm relatively fresh on C programming too, but I always used the command:

gcc test.c - lm
a.out


joshua@TeamJRMobile1:~/C/test$ gcc test.c - lm
gcc: lm: No such file or directory
gcc: -E or -x required when input is from standard input
joshua@TeamJRMobile1:~/C/test$ a.out
bash: a.out: command not found

[zwaardmeester]

try compiling with
gcc ./test.c -otest
to be sure that you give the right file (test.c in current directory) as input

[mtausig]

The code and the compile command look OK to me.
The file where the compiler finds the error, /usr/lib/crt1.o, is part of libc6-dev. Check if you have it installed and maybe try updating it.

[Joeb454]

It might sound stupid - but have you installed build-essential (apt://build-essential) ?

[JoFrRi]

Yes I have installed build-essential as per the first message. I have version 2.8 of libc6-dev. I reinstalled it but unfortunately the same error message.

[Joeb454]

When in the correct directory, try running
gcc ./test.c -o prog
./prog


I can't see anything wrong with the code...

Also - moved to Programming Talk :) (I noticed it wasn't in the correct sub-forum)

[ichi@YUKI]

gcc test.c -otest

this might sound silly but, the code you typed has no space between the switch (-o) and the output file. It should have been


gcc test.c -o test

and then you might be able to run it using a dot-slash.


./test

[malloq]

What does


dpkg -S crt1.o

say?

[snikrot]

You forgot the -c option.



gcc -cHelloworld.c -oHelloword


See also http://fixunix.com/linux/6304-undefined-reference-main.html

[dwhitney67]

I'm relatively fresh on C programming too, but I always used the command:

gcc test.c - lm
a.out
The -lm is used to link in the math library. For applications that do not require such library, it is not necessary to specify -lm.

[fiddler616]

Others seem to have beat me to this, but in general (and IMHO) :

gcc programname.c -o outputname
./outputname
is the way to do it.

[ichi@YUKI]

guys.. dont forget the spaces between the switches and input/output files.. this proves that most programming problems are due to syntax. lol..

[JoFrRi]

What does


dpkg -S crt1.o

say?

joshua@TeamJRMobile1:~/C/test$ dpkg -S crt1.o
libc6-dev: /usr/lib/Scrt1.o
libc6-dev: /usr/lib/Mcrt1.o
libc6-dev: /usr/lib/gcrt1.o
libc6-dev: /usr/lib/crt1.o

[JoFrRi]

Sorry about the multiple posts, the site kept freezing not showing a post and I don't know how to remove them.

[stevescripts]

Did you ever get your hello world program to succesfully compile and run?

Steve

[JoFrRi]

Did you ever get your hello world program to succesfully compile and run?

Steve

Nope. Still haven't got it working.

[stevescripts]

Are you trying to build it from the same directory as the source file?

Are you getting any errors now? If so, please post the output.

The results of building the code sample you pasted, on my Ubuntu box:


steveo@delldesktop:~/Desktop$ gcc test.c -o test
steveo@delldesktop:~/Desktop$ ./test
Hello World


Hope this helps. Hang in there.

Steve

[gnusci]

It seems you have a serious damage in your system, hopefully only your compiler. I recommend you to uninstall and then install the gcc compiler, and then try again. There is anything wrong in your code and procedure to compile it.

[cmay]

actaully more a question. but is there not a warning against using the name "test" instead of hello or testprog ? as there should be on bsd unix and linux a program called test. which can confuse the shell . not that i do not think there is as above post suggest somekind of damage but i posted this as i was not sure if it is correct information i have and if so others that reads this tread whit same problem then maybe might as well rule that one out also.

[dwhitney67]

You are correct cmay; there is a utility called 'test' (in /usr/bin), thus one should avoid naming their executable the same name.

Though based on the help I've seen so far in this thread, it shouldn't be an issue, if the OP happens to use the name 'test', and runs his application such as:

./test
This ensures that the file in the local directory is executed, and not the one in /usr/bin.

[JoFrRi]

Hey everyone, thanks for all your help. I've removed and am reinstalling Ubuntu from scratch. Doing some system updates and then I will get back at it. I will let you guys know how it goes.

[JoFrRi]

Well it's a new day and a new Ubuntu. I removed the old copy, reinstalled a new copy, installed all the system updates and build-essential and now the program compiles and runs fine. Thanks for all the help, you guys are great!

[Tony Flury]

As a matter of interest why did you reinstall Ubuntu - that might be a normal tactic for Windows (i know somone who reinstalls Windows XP every month), but I can't see that being neccessary for Ubuntu, unless it was massively messed up (like giving kernel panics etc).

[JoFrRi]

I reinstalled Ubuntu because I had just installed it and there were issues. If there is an issue with one thing chances are, there are going to be more problems. From past experience, if an install went bad, I would wipe it and start over and it has worked well so far.