Getting your C++ program to run

wizard:cpp graham$ g++ morethan.cpp

morethan.cpp:9:18: error: ir.inc: No such file or directory

morethan.cpp: In function  •[98]int main() •[99]:

morethan.cpp:27: error:  •[98]intread •[99] was not declared in this scope

What happened? An "include" file was missing ... it couldn't be found (first error), nor could symbols that were defined in it (second error)
Solution: Copy the include file into the current directory (have you only downloaded part of an application?)

wizard:cpp graham$ g++ morethan.cpp

Undefined symbols:

  "intread(char const*)", referenced from:

      _main in ccOOqa9r.o

      _main in ccOOqa9r.o

ld: symbol(s) not found

collect2: ld returned 1 exit status

What happened? The compile worked, but then you failed to link the compiler output to all the other components needed to make up an application.
Solution: Add the name of the other files that make up the application onto the compile / load command
OR Solution: Specify just compile (-c option) not compile and load (default)

wizard:cpp graham$ g++ morethan.cpp ir.cpp

wizard:cpp graham$

What happened? It worked ... "no news is good news" BUT where it the output file (the program)
Solution: It's in a file called a.out - that's the [very curious] default

wizard:cpp graham$ a.out

-bash: a.out: command not found

What happened? Your PATH doesn't include the current directory, so when you tried to run a.out it didn't look in the right place for it
Solution: Add current directory to PATH (but be aware of security issues)

wizard:cpp graham$ ./a.out

Enter year of first book 2006

Enter year of second book 2004

First book is newer

Age difference is 2

first book: 2006

second book: 2004

What happened? It worked!

wizard:cpp graham$ g++ -o moreisless morethan.cpp ir.cpp

wizard:cpp graham$

What happened? Compile, link / load and the output file is named this time

wizard:cpp graham$ ./moreisless

Enter year of first book 2010

Enter year of second book 2011

First book is older

Age difference is 1

first book: 2010

second book: 2011

What happened? It worked!

The source code used in this example can be found in our Introduction to C++ resource bundle
(written 2010-11-15, updated 2010-11-16)

Associated topics are indexed under

C051 - C and C based languages - C++ - General
  [3587] C++ Courses - do I get official certification at the end of my Well House course? - (2012-01-20)
  [3250] C++ - how we teach the language and the concepts behind the language - (2011-04-17)
  [3155] Rake - a build system using code written in Ruby - (2011-02-03)
  [3129] Extra courses - C and C++ - (2011-01-12)
  [3067] Using C and C++ functions in the same program - how to do it - (2010-11-24)
  [2851] Further C++ material - view new or old - (2010-07-04)
  [2763] Our C and C++ training course are on Open Source platforms - (2010-05-13)
  [2577] Complete teaching example - C++, inheritance, polymorphism - (2010-01-15)
  [2536] All the Cs ... and Java too - (2009-12-13)
  [2504] Learning to program in ... - (2009-11-15)
  [2370] C++, Python, and other training - do we use an IDE - (2009-08-21)

C231 - C and C based languages - Introduction to C++
  [3069] Strings, Garbage Collection and Variable Scope in C++ - (2010-11-25)
  [3053] Make - automating the commands for building and installing - (2010-11-16)
  [2845] Objects and Inheritance in C++ - an easy start - (2010-07-01)
  [2169] When should I use OO techniques? - (2009-05-11)
  [2004] Variable Scope in C++ - (2009-01-22)
  [928] C++ and Perl - why did they do it THAT way? - (2006-11-16)
  [336] Targetted Advertising - (2005-06-05)
  [318] Choosing a theme - (2005-05-20)
  [317] Programming languages - a comparison - (2005-05-20)

Back to
Positively reforming the system - could it be done?

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Horse's mouth home

Forward to
Make - automating the commands for building and installing

Some other Articles

C++ - a complete example with polymorphism, and how to split it into project files
Zyliana Kyrei Cox
Longhope Hotel
Getting your C++ program to run
Positively reforming the system - could it be done?
Views of Melksham - November 2010
Computer Graphics is fun - even if Java Applets are Old Hat
String handling - from first steps to practical examples
What is a universal superclass? Java / Perl / Python / Other OO languages

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