Compiling Files

<BODY LANG="EN"> <HR><center> <table border=1> <td><A NAME="tex2html19" HREF="c13.shtml"><img height=36 width=36 alt="PREVIOUS" src="http://www.cs.utah.edu/icons/latex2html/previous.gif"></A></td> <td><A NAME="tex2html25" HREF="c13.shtml"><img height=36 width=36 alt="UP" src="http://www.cs.utah.edu/icons/latex2html/up.gif"></A></td> <td><A NAME="tex2html27" HREF="node2.shtml"><img height=36 width=36 alt="NEXT" src="http://www.cs.utah.edu/icons/latex2html/next.gif"></A></td> <td><a href="contents-node1.shtml"><img height=36 width=36 alt="CONTENTS" src="http://www.cs.utah.edu/icons/latex2html/toc.gif"></a></td> <td><a href="reset.hamlet"><img height=36 width=36 alt="RESET" src="http://www.cs.utah.edu/icons/latex2html/stop.gif"></a></td> <td><a href="copyright.html"><img height=36 width=36 alt="COPYRIGHT" src="http://www.cs.utah.edu/icons/latex2html/copyright.gif"></a></td> <td><a href="mailto:hamlet@cs.utah.edu"><img height=36 width=36 alt="FEEDBACK" src="http://www.cs.utah.edu/icons/latex2html/feedback.gif"></a></td> <td>     <a href="http://www.cs.utah.edu/%7Ehamlet/icons.html"><img height=36 width=36 alt=ABOUT src=http://www.cs.utah.edu/icons/latex2html/about.gif></a>  </td> </table> </center> <HR><H1><A NAME="SECTION00010000000000000000">Compiling Files</A></H1> <P> Up to this point, whenever you wanted to compile a program you compiled the file displayed in an Emacs buffer. The <B>Compile This File...</B> option of Emacs' <B>Compile</B> menu (or equivalently, <B> M-x compile</B>) is a handy feature when your entire program is contained with one file. It is, of course, possible to compile a file completely independently of Emacs. <P> Inside the UNIX Shell window, connect to the <B>separate1</B> directory that is contained with the <B>examples</B> directory of your home directory. What does it contain? <P> <P><A NAME="tex2html4" HREF="answer20.html">Click here for the answer</A><P> <P> This program prints out ``Hello world'', and you can compile and run it without ever displaying it in Emacs. To compile it, type the following into your UNIX Shell window: <P> <PRE>gcc -Wall -c hello.c</PRE> <P> This command resulted in a new file being created in the ``separate1'' directory to which you are currently connected. Use the <B>ls</B> command to list the directory. What is the new file? <P> <P><A NAME="tex2html5" HREF="answer24.html">Click here for the answer</A><P> <P> At this point you still don't have an executable program that you can run. The next step is to link the object file to produce such an executable. To do this, type the following into your UNIX Shell window: <P> <PRE>gcc -o hello hello.o -lm</PRE> <P> Linking hooks up your compiled code with some additional C-specific code. Once again, a new file has been created in the ``separate1'' directory. List the directory. What new file do you find? <P> <P><A NAME="tex2html6" HREF="answer27.html">Click here for the answer</A><P> <P> Now that you have an executable you can run it in the familiar way. Simply type ``hello'' into the UNIX Shell window. <P> To summarize, the steps involved in compiling, linking, and running a program are: <P> <OL> <LI> Compile the ``.c'' file containing the source code with a command such as <P> <PRE>gcc -Wall -c hello.c</PRE> <P> The <TT>-c</TT> in the command is important--it tells C to produce an object file called (in this case) ``hello.o''. The <TT>-Wall</TT> part is optional but is strongly encouraged--it tells C to produce all possible warning messages. A warning message will usually lead you to a bug in your program. <LI> Link the ``.o'' file to produce an executable with a command such as <P> <PRE>gcc -o hello hello.o -lm</PRE> <P> The <TT>-o hello</TT> in the command is important--it tells C what to name the executable. The <TT>-lm</TT> part tells C to link in the math libraries. If your program doesn't use any of the match functions from ``math.h'', you can leave this part out. <LI> Run the executable in the usual way. <P> If your entire program is contained within a <I>single</I> file, you can do the compilation and linking in one step by entering the command <P> <PRE>gcc -Wall -o hello hello.c -lm</PRE> <P> </OL> <P> This is exactly what Emacs does when it compiles a program for you. We have been careful in this lesson to do the compilation in two separate steps so that you will be able to deal with programs made up of more than one file. We will explore this topic further in the next lesson. <P> <HR><center> <table border=1> <td><A NAME="tex2html19" HREF="c13.shtml"><img height=36 width=36 alt="PREVIOUS" src="http://www.cs.utah.edu/icons/latex2html/previous.gif"></A></td> <td><A NAME="tex2html25" HREF="c13.shtml"><img height=36 width=36 alt="UP" src="http://www.cs.utah.edu/icons/latex2html/up.gif"></A></td> <td><A NAME="tex2html27" HREF="node2.shtml"><img height=36 width=36 alt="NEXT" src="http://www.cs.utah.edu/icons/latex2html/next.gif"></A></td> <td><a href="contents-node1.shtml"><img height=36 width=36 alt="CONTENTS" src="http://www.cs.utah.edu/icons/latex2html/toc.gif"></a></td> <td><a href="reset.hamlet"><img height=36 width=36 alt="RESET" src="http://www.cs.utah.edu/icons/latex2html/stop.gif"></a></td> <td><a href="copyright.html"><img height=36 width=36 alt="COPYRIGHT" src="http://www.cs.utah.edu/icons/latex2html/copyright.gif"></a></td> <td><a href="mailto:hamlet@cs.utah.edu"><img height=36 width=36 alt="FEEDBACK" src="http://www.cs.utah.edu/icons/latex2html/feedback.gif"></a></td> <td>     <a href="http://www.cs.utah.edu/%7Ehamlet/icons.html"><img height=36 width=36 alt=ABOUT src=http://www.cs.utah.edu/icons/latex2html/about.gif></a>  </td> </table> </center> <HR><P><ADDRESS> <I><A NAME="tex2html1" HREF="http://www.cs.utah.edu/~hamlet">Hamlet Project</A> <BR> <A NAME="tex2html2" HREF="mailto:hamlet@cs.utah.edu">hamlet@cs.utah.edu</A></I> </ADDRESS> </BODY>