Getting Started with C/C++ on the UM Research Server

• What is willow's IP address?
  130.74.110.16.
  

• Do I use telnet/FTP, or secure shell/SFTP, to connect to willow and tranfer files from willow?
  Telnet and FTP have been disabled on willow for security purposes, so your only choice is secure shell/SFTP. See more information on secure shell.
  

• How can I apply for an individual account, or a set of class accounts, on willow?
  Follow the instructions under Non-Research Account Categories on the MCSR Accounts page.
  

• What C compilers are installed on willow?
  The GNU C Compiler and the SUN STUDIO 8 C/C++ Compilers.
  

• What environment variable settings are necessary for me to compile C/C++ programs on willow?
  Your PATH environment variable should simply contain /usr/local/bin, since this is where the compiler exectuables are located on willow. Also, the LD_LIBRARY_PATH should include the path /usr/local/lib.Otherwise, the executable created by
  the compiler will cause an error due to the library link problem.
  

• What suffixes should I give to my C and C++ source files, to ensure proper processing?
  .cpp, .cc, or .C for C++ programs that are to be preprocessed, compiled and assembled
  .c, for C programs that are to be processed, compiled, and assembled
  .h for preprocessor (header) files; not usually named on command line.
  to top

• How can I compile and link a C program on willow with the gcc compiler?
  gcc file1.c file2.c ...
  

• How can I compile and link a C++ source program on willow with the gcc compiler?
  g++ file1.cpp file2.cpp ...
  

• How can I tell the compiler where to find an included preprocessor (.h) file that is not in the current compilation directory or in any of the default system include directories?
  By using
  -Idirectory
  Which says to look in the directory named directory. For example, if you want to compile program bball.cpp which has a directive including preprocessor file bball.h as follows: #include "bball.h"
  the compiler will find it if you specify:
  g++ ball.cpp -I/tmp
  

• How can I compile one or more C++ source files into object files, without yet linking them into an executable program?
  By using the -c option, which supresses the linking phase of compilation, as follows:
  g++ -c file1.cpp
  which will create one object (.o) file for each source file compiled, but will not create an a.out file.
  

• How can I ensure that the compiler can find/link a C/C++ library module that my program calls?
  By using
  -llibrary
  Which says to use the library named library when linking.
  The linker searches a standard list of directories for the library, which is actually a file named
  `liblibrary.a'. The linker then uses this file as if
  it had been specified precisely by name.
  The directories searched include several standard system directories plus any that you specify with `-L'.
  Normally the files found this way are library files-archive files whose members are object files. The linker handles an archive file by scanning through it for members which define symbols that have so far been referenced but not defined. However, if the linker finds an ordinary object file rather than a library, the object file is linked in the usual fashion. The only difference between using an `-l' option and specifying a file name is that `-l' surrounds library with `lib' and `.a' and searches several directories.
  Example: If you have compiled a function playGame() into an object file, and archived that object file as a member in an archive library file called libroundball.a, which is in directory /tmp, and you want to compile a program in file bball.cpp which makes a call to playGame(), you would compile/link as follows:
  g++ myfile.cpp -L/tmp -lroundball
  which tells the compiler to look in directory /tmp for a library called libroundball.a to find any otherwise undefined symbols--namely, playGame()
  

• How can I create a C/C++ library module in an archive directory, so that it may be called (and found) by other programs on willow?
  By using the Unix archive command ar.
  Example: The following example will compile a reusable function playGame() into an object file, then add that object file as a member of a new library archive called libroundball.a:
  g++ -c playGame.cpp
  /usr/ccs/bin/ar -rc libroundball.a playGame.o
  for more information, see man ar
  

• How can I tell the compiler what to name the executable program--other than a.out?
  With the -o option, like this:
  g++ -o myfile.exe myfile.cpp
  which will will put your executable program in myfile.exe
  

• When I try to compile/link my C++ program, why do I get this error message:
  Undefined symbol...ld: fatal: Symbol referencing errors. No output written to a.out.
  Your program is probably calling a function, the object code for which cannot be found by the loader.
  If you are trying to call a function defined in another, separately compiled program, make sure that you have included that programs object file (.o file) in the command line.
  If you are trying to call a function defined in static library, make sure you specify on the command line the name of the library (-llibrary) and it's location in the file system (-Ldirectory).
  (See the q/a above on library modules.)
  

• When I try to execute my a.out program, why do I get error message:
  a.out: not found.
  You can fix this by either prepending the command with ./, as in:
  ./a.out
  Or by adding the current directory to your PATH environment variable.
  See also: Path Lists environment variables, problems running shell scripts, and managing your environment.