C++ on ubuntu hello world

Question

I'm trying to write my first code on ubuntu terminal using c++ .I created a new cpp file named aaa by

"nano aaa.cpp"

then inside I wrote

#include<iostream>
using std::cout;
using std::endl;

int main(int argc, car** argv)
{
   cout << "hello" << endl;
   return 0; 
}

i saved and got out but when i tried typing

g++ aaa.cpp

I got the error

error: ‘endl’ was not declared in this scope cout << "hello" << endl;

where did I go wrong I tried

$ sudo apt-get remove g++ libstdc++-6.4.7-dev
$ sudo apt-get install build-essential g++-multilib

but it was no good

any help?

Don't use `std::endl` unless you need the extra stuff that it does. `'\n`' ends a line. But `#include ` will get you the declaration for `std::endl`. — Pete Becker, Oct 01 '16 at 15:17
@NickA - that would leave `std::cout` undefined, as well. It's clearly a typo in the example code, not the original. — Pete Becker, Oct 01 '16 at 15:19
The first error should be something like `error: ‘include’ does not name a type \n include`, and you should fix it first. — Lee Duhem, Oct 01 '16 at 15:19
@Pete Becker `endl` is also a member of `ostream` so including `iostream` would already include `endl`. Including `iomanip` would be no help. — Nick is tired, Oct 01 '16 at 15:21
The `main()` signature also has an error which I fixed in my answer below which already received two generous downvotes. — Dirk Eddelbuettel, Oct 01 '16 at 15:23
The signature for main should be `int main(int argc, char** argv)`, not `int main(int argc, car** argv)` as you wrote here. — Emilio Garavaglia, Oct 01 '16 at 15:32

Dirk Eddelbuettel · Accepted Answer · 2016-10-01T15:28:55.657

2

Stylistically, I prefer to be explicit: std::cout and std::endl.

#include <iostream>

int main(int argc, char** argv) {
  std::cout << "hello" << std::endl;
  return 0; 
}

This also fixes a tyo of yours: char, not car and repairs the #include.

This works as expected:

$ g++ -Wall -pedantic -o foo2 foo2.cpp
$ ./foo2
hello
$

If you wanted to, you could also use

using namespace std;

but as stated, I prefer to more explicit form.

Edit: Nothing as much fun as debating the beancounters. OP question is likely having _another error he is not sharing. His code, repaired for char actually builds:

$ cat foo3.cpp 
#include <iostream>
using std::cout;
using std::endl;

int main(int argc, char** argv) {
  cout << "hello" << endl;
  return 0; 
}
$ g++ -Wall -pedantic -o foo3 foo3.cpp
$ ./foo3
hello
$

Ubuntu 16.04, g++ 5.4.0

edited Oct 01 '16 at 15:28

answered Oct 01 '16 at 15:20

Dirk Eddelbuettel

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3

Fun morning. Two drive-by downvotes without comments? Awesome. – Dirk Eddelbuettel Oct 01 '16 at 15:22
Well, you haven't answered the question being asked here. – juanchopanza Oct 01 '16 at 15:24
Yes I did: `std::endl`. Explicit reference. – Dirk Eddelbuettel Oct 01 '16 at 15:25
OK I see. But `using std::endl;` takes care of that, so this doesn't present a solution (except for the typo in the main function parameters.) – juanchopanza Oct 01 '16 at 15:25
Doesn't explain his compiler error. He _must_ have another one. – Dirk Eddelbuettel Oct 01 '16 at 15:27
3

Right. Because there is not enough information in the question. Also, your suggestion of `using namespace std;` is unnecessary and worse than what OP already has. – juanchopanza Oct 01 '16 at 15:33
You are a real treasure. I mentioned it for fscking completeness and do not use it my answer. – Dirk Eddelbuettel Oct 01 '16 at 15:34
1

And then you wonder why people don't leave comments when they down-vote. – juanchopanza Oct 01 '16 at 15:35
You are effing wrong. Whether to selectively include (`using std::foo`) or to explicitly refer (`std::foo`) is equivalent. I don;t like your suggestion as it bloats the top-part of the file. I _like_ the explicit reference especially when I work with multiple namespaces. – Dirk Eddelbuettel Oct 01 '16 at 15:37
Also real impressive that you now admit that you were wrong earlier, yet don't lift the downvote. Stay classy, San Diego. – Dirk Eddelbuettel Oct 01 '16 at 15:38
Anyway, the question was low quality and I voted for it to be closed. May as well be deleted. – Dirk Eddelbuettel Oct 01 '16 at 15:39
1

I wasn't wrong, and I didn't admit any such thing. I haven't changed my judgment of your answer, although I agree with your coding style suggestion. But that is tangential to the problem reported here. – juanchopanza Oct 01 '16 at 15:39
So you confirm that you can't read, or don't understand conditionals. Else you would have seen my `If you wanted to ...but I prefer to more explicit form.` (Which needs a `s/to/the/` ...) – Dirk Eddelbuettel Oct 01 '16 at 15:41

cyrildz · Answer 2 · 2017-07-02T11:20:34.360

First, make sure you have the tools you need to be able to compile a C++ code on Ubuntu. For that run the following code in the command line : This line will install all the basic stuff you need for compiling a C++ code, it will install C, C++, and make.

 sudo apt-get install build-essential

Now that you have all you need, I will suggere to explicetely using std::cout / std::endl . That way you don't import all the stuff available under the namespace std that you are not using. Using std::cout / std::endl shows clearly the origin the instance you are using. Notice : you have an error in the main function argument, namely : car, it should be char

#include<iostream>
int main(int argc, char** argv)
{
   std::cout << "hello" << std::endl;
   return 0; 
}

Now you can compile and run your code this way : in this example I'm calling the executable file "hello"

g++ -Wall -o hello aaa.cpp
./hello

C++ on ubuntu hello world

any help?

2 Answers2