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diff --git a/en_US.ISO_8859-1/articles/programming-tools/article.sgml b/en_US.ISO_8859-1/articles/programming-tools/article.sgml deleted file mode 100644 index 65e1f87d26..0000000000 --- a/en_US.ISO_8859-1/articles/programming-tools/article.sgml +++ /dev/null @@ -1,1835 +0,0 @@ -<!-- $Id: article.sgml,v 1.4 1998-08-09 22:53:51 wosch Exp $ --> -<!-- The FreeBSD Documentation Project --> - -<!DOCTYPE BOOK PUBLIC "-//Davenport//DTD DocBook V3.0//EN"> -<book> -<bookinfo> -<bookbiblio> -<title>A User's Guide to FreeBSD Programming Tools</title> - -<authorgroup> -<author> -<firstname>James</firstname> -<surname>Raynard</surname> -<affiliation> -<address> -<email>jraynard@freebsd.org</email> -</address> -</affiliation> -</author></authorgroup> - -<pubdate>August 17, 1997</pubdate> - -<copyright> -<year>1997</year> -<holder>James Raynard</holder> -</copyright> - -<abstract><para>This document is an introduction to using some of the programming -tools supplied with FreeBSD, although much of it will be applicable to -many other versions of Unix. It does <emphasis>not</emphasis> attempt to describe -coding in any detail. Most of the document assumes little or no -previous programming knowledge, although it is hoped that most -programmers will find something of value in it</para></abstract> -</bookbiblio> -</bookinfo> - -<chapter> -<title>Introduction<anchor id=foo></title> - -<para>FreeBSD offers an excellent development environment. Compilers -for C, C++, and Fortran and an assembler come with the basic system, -not to mention a Perl interpreter and classic Unix tools such as -<command>sed</> and <command>awk</>. If that is not enough, there are -many more compilers and interpreters in the Ports collection. FreeBSD -is very compatible with standards such as <acronym>POSIX</> and -<acronym>ANSI</> C, as well with its own BSD heritage, so it is -possible to write applications that will compile and run with little -or no modification on a wide range of platforms.</para> - -<para>However, all this power can be rather overwhelming at first if -you've never written programs on a Unix platform before. This -document aims to help you get up and running, without getting too -deeply into more advanced topics. The intention is that this document -should give you enough of the basics to be able to make some sense of -the documentation.</para> - -<para>Most of the document requires little or no knowledge of -programming, although it does assume a basic competence with using -Unix and a willingness to learn!</para> - -</chapter> - -<chapter> -<title>Introduction to Programming</title> - -<para>A program is a set of instructions that tell the computer to do -various things; sometimes the instruction it has to perform depends -on what happened when it performed a previous instruction. This -section gives an overview of the two main ways in which you can give -these instructions, or <quote>commands</quote> as they are usually -called. One way uses an <firstterm>interpreter</>, the other a -<firstterm>compiler</>. As human languages are too difficult for a -computer to understand in an unambiguous way, commands are usually -written in one or other languages specially designed for the -purpose.</para> - - - -<sect1> -<title>Interpreters</title> - -<para>With an interpreter, the language comes as an environment, where you -type in commands at a prompt and the environment executes them for -you. For more complicated programs, you can type the commands into a -file and get the interpreter to load the file and execute the commands -in it. If anything goes wrong, many interpreters will drop you into a -debugger to help you track down the problem.</para> - -<para>The advantage of this is that you can see the results of your -commands immediately, and mistakes can be corrected readily. The -biggest disadvantage comes when you want to share your programs with -someone. They must have the same interpreter, or you must have some -way of giving it to them, and they need to understand how to use it. -Also users may not appreciate being thrown into a debugger if they -press the wrong key! From a performance point of view, interpreters -can use up a lot of memory, and generally do not generate code as -efficiently as compilers.</para> - -<para>In my opinion, interpreted languages are the best way to start -if you have not done any programming before. This kind of environment -is typically found with languages like Lisp, Smalltalk, Perl and -Basic. It could also be argued that the Unix shell (<command>sh</>, -<command>csh</>) is itself an interpreter, and many people do in fact -write shell <quote>scripts</quote> to help with various -<quote>housekeeping</> tasks on their machine. Indeed, part of the -original Unix philosophy was to provide lots of small utility -programs that could be linked together in shell scripts to perform -useful tasks.</para> - -</sect1> - -<sect1> -<title>Interpreters available with FreeBSD</title> - -<para>Here is a list of interpreters that are available as <ulink -URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/">FreeBSD -packages</ulink>, with a brief discussion of some of the more popular -interpreted languages. </para> - -<para>To get one of these packages, all you need to do is to click on -the hotlink for the package, then run -<screen>$ <userinput>pkg_add <replaceable>package name</></userinput></screen> -</para> - -<para>as root. Obviously, you will need to have a fully functional FreeBSD -2.1.0 or later system for the package to work!</para> - -<para> -<variablelist> -<varlistentry><term><acronym>BASIC</></term> - -<listitem><para>Short for Beginner's All-purpose Symbolic Instruction -Code. Developed in the 1950s for teaching University students to -program and provided with every self-respecting personal computer in -the 1980s, <acronym>BASIC</> has been the first programming language -for many programmers. It's also the foundation for <trademark>Visual -Basic</>.</para> - -<para>The <ulink -URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/lang/bwbasic-2.10.tgz">Bywater -Basic Interpreter</ulink> and the <ulink -URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/lang/pbasic-2.0.tgz">Phil -Cockroft's Basic Interpreter</ulink> (formerly Rabbit Basic) are -available as FreeBSD <ulink -URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/">FreeBSD -packages</ulink></para> -</listitem> -</varlistentry> - -<varlistentry><term>Lisp</term> -<listitem><para>A language that was developed in the late 1950s as an alternative to -the <quote>number-crunching</quote> languages that were popular at the time. -Instead of being based on numbers, Lisp is based on lists; in fact -the name is short for <quote>List Processing</quote>. Very popular in AI -(Artificial Intelligence) circles.</para> - -<para>Lisp is an extremely powerful and sophisticated language, but -can be rather large and unwieldy. </para> - -<para>FreeBSD has <ulink -URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/gcl-2.0.tgz">GNU -Common Lisp</ulink> available as a package.</para> - -</listitem> -</varlistentry> - -<varlistentry><term>Perl</term> -<listitem><para>Very popular with system administrators for writing -scripts; also often used on World Wide Web servers for writing <acronym>CGI</> -scripts.</para> - -<para>Version 4, which is probably still the most widely-used -version, comes with FreeBSD; the newer <ulink -URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/lang/perl-5.001.tgz">Perl -Version 5</ulink> is available as a package.</para> - -</listitem> -</varlistentry> - -<varlistentry><term>Scheme</term> -<listitem><para>A dialect of Lisp that is rather more compact and -cleaner than Common Lisp. Popular in Universities as it is simple -enough to teach to undergraduates as a first language, while it has a -high enough level of abstraction to be used in research work.</para> - -<para>FreeBSD has packages of the -<ulink URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/lang/elk-3.0.tgz">Elk Scheme Interpreter</ulink>, the -<ulink URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/lang/mit-scheme-7.3.tgz">MIT Scheme Interpreter</ulink> and the -<ulink URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/lang/scm-4e1.tgz">SCM Scheme Interpreter</ulink>.</para> - -</listitem> -</varlistentry> - -<varlistentry><term>Icon</term> -<listitem><para><ulink URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/lang/icon-9.0.tgz">The Icon Programming Language</ulink>.</para> -</listitem> -</varlistentry> - -<varlistentry><term>Logo</term> -<listitem><para><ulink URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/lang/ucblogo-3.3.tgz">Brian Harvey's LOGO Interpreter</ulink>.</para> -</listitem> -</varlistentry> - -<varlistentry><term>Python</term> -<listitem><para><ulink URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/lang/python-1.2">The Python Object-Oriented Programming Language</ulink></para> -</listitem> -</varlistentry> - -</variablelist> -</para> - -</sect1> - -<sect1> -<title>Compilers</title> - -<para>Compilers are rather different. First of all, you write your -code in a file (or files) using an editor. You then run the compiler -and see if it accepts your program. If it did not compile, grit your -teeth and go back to the editor; if it did compile and gave you a -program, you can run it either at a shell command prompt or in a -debugger to see if it works properly.<footnote><para>If you run it in -the shell, you may get a core dump.</para></footnote></para> - -<para>Obviously, this is not quite as direct as using an interpreter. -However it allows you to do a lot of things which are very difficult -or even impossible with an interpreter, such as writing code which -interacts closely with the operating system—or even writing -your own operating system! It's also useful if you need to write very -efficient code, as the compiler can take its time and optimise the -code, which would not be acceptable in an interpreter. And -distributing a program written for a compiler is usually more -straightforward than one written for an interpreter—you can just -give them a copy of the executable, assuming they have the same -operating system as you.</para> - -<para>Compiled languages include Pascal, C and C++. C and C++ are rather -unforgiving languages, and best suited to more experienced -programmers; Pascal, on the other hand, was designed as an educational -language, and is quite a good language to start with. Unfortunately, -FreeBSD doesn't have any Pascal support, except for a Pascal-to-C -converter in the ports.</para> - -<para>As the edit-compile-run-debug cycle is rather tedious when -using separate programs, many commercial compiler makers have -produced Integrated Development Environments (<acronym>IDE</acronym>s -for short). FreeBSD does not have an <acronym>IDE</> as such; however -it is possible to use Emacs for this purpose. This is discussed in -<xref linkend="emacs">.</para> - -</sect1> -</chapter> - -<chapter> -<title>Compiling with <command>cc</command></title> - -<para>This section deals only with the GNU compiler for C and C++, -since that comes with the base FreeBSD system. It can be invoked by -either <command>cc</> or <command>gcc</>. The details of producing a -program with an interpreter vary considerably between interpreters, -and are usually well covered in the documentation and on-line help -for the interpreter.</para> - -<para>Once you've written your masterpiece, the next step is to convert it -into something that will (hopefully!) run on FreeBSD. This usually -involves several steps, each of which is done by a separate -program.</para> - -<procedure> -<step><para>Pre-process your source code to remove comments and do other -tricks like expanding macros in C. -</para></step> - -<step><para>Check the syntax of your code to see if you have obeyed the -rules of the language. If you have not, it will complain! -</para></step> - -<step><para>Convert the source code into assembly -language—this is very close to machine code, but still -understandable by humans. Allegedly.<footnote><para>To be strictly -accurate, <command>cc</> converts the source code into its own, -machine-independent <firstterm>p-code</> instead of assembly language -at this stage.</para></footnote></para></step> - -<step><para>Convert the assembly language into machine -code—yep, we are talking bits and bytes, ones and zeros -here.</para></step> - -<step><para>Check that you have used things like functions and global -variables in a consistent way. For example, if you have called a -non-existent function, it will complain.</para></step> - -<step><para>If you are trying to produce an executable from several -source code files, work out how to fit them all together.</para></step> - -<step><para>Work out how to produce something that the system's run-time -loader will be able to load into memory and run.</para></step> - -<step><para>Finally, write the executable on the file -system.</para></step> - -</procedure> - -<para>The word <firstterm>compiling</> is often used to refer to just -steps 1 to 4—the others are referred to as -<firstterm>linking</>. Sometimes step 1 is referred to as -<firstterm>pre-processing</> and steps 3-4 as -<firstterm>assembling</>.</para> - -<para>Fortunately, almost all this detail is hidden from you, as -<command>cc</> is a front end that manages calling all these programs -with the right arguments for you; simply typing -<screen>$ <userinput>cc foobar.c</></screen></para> - -<para>will cause <filename>foobar.c</> to be compiled by all the -steps above. If you have more than one file to compile, just do -something like -<screen>$ <userinput>cc foo.c bar.c</></screen> -</para> - -<para>Note that the syntax checking is just that—checking the -syntax. It will not check for any logical mistakes you may have made, -like putting the program into an infinite loop, or using a bubble -sort when you meant to use a binary sort.<footnote><para>In case you -didn't know, a binary sort is an efficient way of sorting things into -order and a bubble sort isn't.</para></footnote></para> - -<para>There are lots and lots of options for <command>cc</>, which -are all in the man page. Here are a few of the most important ones, -with examples of how to use them.</para> - -<variablelist> -<varlistentry><term><option>-o <replaceable>filename</replaceable></></term> - -<listitem><para>The output name of the file. If you do not use this -option, <command>cc</> will produce an executable called -<filename>a.out</>.<footnote><para>The reasons for this are buried in -the mists of history.</para></footnote></para> - -<informalexample> -<screen>$ <userinput>cc foobar.c</> <lineannotation>executable is <filename>a.out</></> -$ <userinput>cc -o foobar foobar.c</> <lineannotation>executable is <filename>foobar</></></screen> -</informalexample> -</listitem> -</varlistentry> - -<varlistentry><term><option>-c</option></term> -<listitem><para>Just compile the file, do not link it. Useful for toy -programs where you just want to check the syntax, or if you are using -a <filename>Makefile</filename>.</para> - -<informalexample> -<screen>$ <userinput>cc -c foobar.c</userinput></screen> -</informalexample> - -<para>This will produce an <firstterm>object file</> (not an -executable) called <filename>foobar.o</filename>. This can be linked -together with other object files into an executable.</para> - -</listitem> -</varlistentry> - -<varlistentry><term><option>-g</option></term> - -<listitem><para>Create a debug version of the executable. This makes -the compiler put information into the executable about which line of -which source file corresponds to which function call. A debugger can -use this information to show the source code as you step through the -program, which is <emphasis>very</emphasis> useful; the disadvantage -is that all this extra information makes the program much bigger. -Normally, you compile with <option>-g</option> while you are -developing a program and then compile a <quote>release -version</quote> without <option>-g</option> when you're satisfied it -works properly.</para> - -<informalexample> -<screen>$ <userinput>cc -g foobar.c</userinput></screen> -</informalexample> - -<para>This will produce a debug version of the -program.<footnote><para>Note, we didn't use the <option>-o</option> -flag to specify the executable name, so we will get an executable -called <filename>a.out</filename>. Producing a debug version called -<filename>foobar</filename> is left as an exercise for the -reader!</para></footnote></para> - -</listitem> -</varlistentry> - -<varlistentry><term><option>-O</option></term> - -<listitem><para>Create an optimised version of the executable. The -compiler performs various clever tricks to try and produce an -executable that runs faster than normal. You can add a number after -the <option>-O</option> to specify a higher level of optimisation, -but this often exposes bugs in the compiler's optimiser. For -instance, the version of <command>cc</command> that comes with the -2.1.0 release of FreeBSD is known to produce bad code with the -<option>-O2</option> option in some circumstances.</para> - -<para>Optimisation is usually only turned on when compiling a release -version.</para> - -<informalexample> -<screen>$ <userinput>cc -O -o foobar foobar.c</userinput></screen> -</informalexample> - -<para>This will produce an optimised version of -<filename>foobar</filename>.</para> - -</listitem> -</varlistentry> -</variablelist> - -<para>The following three flags will force <command>cc</command> to -check that your code complies to the relevant international standard, -often referred to as the <acronym>ANSI</acronym> standard, though -strictly speaking it is an <acronym>ISO</acronym> standard.</para> - -<variablelist> - -<varlistentry><term><option>-Wall</option></term> - -<listitem><para>Enable all the warnings which the authors of -<command>cc</command> believe are worthwhile. Despite the name, it -will not enable all the warnings <command>cc</command> is capable -of.</para></listitem> - -</varlistentry> - -<varlistentry><term><option>-ansi</option></term> - -<listitem> -<para>Turn off most, but not all, of the non-<acronym>ANSI</> C -features provided by <command>cc</command>. Despite the name, it does -not guarantee strictly that your code will comply to the -standard.</para> -</listitem> - -</varlistentry> - -<varlistentry><term><option>-pedantic</option></term> - -<listitem> -<para>Turn off <emphasis>all</emphasis> -<command>cc</command>'s non-<acronym>ANSI</> C features.</para> -</listitem> - -</varlistentry> -</variablelist> - -<para>Without these flags, <command>cc</command> will allow you to -use some of its non-standard extensions to the standard. Some of -these are very useful, but will not work with other compilers—in -fact, one of the main aims of the standard is to allow people to -write code that will work with any compiler on any system. This is -known as <firstterm>portable code</firstterm>.</para> - -<para>Generally, you should try to make your code as portable as -possible, as otherwise you may have to completely re-write the -program later to get it to work somewhere else—and who knows -what you may be using in a few years time?</para> - -<informalexample> -<screen>$ <userinput>cc -Wall -ansi -pedantic -o foobar foobar.c</userinput></screen> -</informalexample> - -<para>This will produce an executable <filename>foobar</filename> -after checking <filename>foobar.c</filename> for standard -compliance.</para> - -<variablelist> - -<varlistentry><term><option>-l<replaceable>library</replaceable></option></term> - -<listitem><para>Specify a function library to be used during when -linking.</para> - -<para>The most common example of this is when compiling a program that -uses some of the mathematical functions in C. Unlike most other -platforms, these are in a separate library from the standard C one -and you have to tell the compiler to add it.</para> - -<para>The rule is that if the library is called -<filename>lib<replaceable>something</replaceable>.a</filename>, you -give <command>cc</command> the argument -<option>-l<replaceable>something</replaceable></option>. For example, -the math library is <filename>libm.a</filename>, so you give -<command>cc</command> the argument <option>-lm</option>. A common -<quote>gotcha</quote> with the math library is that it has to be the -last library on the command line.</para> - -<informalexample> -<screen>$ <userinput>cc -o foobar foobar.c -lm</userinput></screen> -</informalexample> - -<para>This will link the math library functions into -<filename>foobar</filename>.</para> - -<para>If you are compiling C++ code, you need to add -<option>-lg++</option>, or <option>-lstdc++</option> if you are using -FreeBSD 2.2 or later, to the command line argument to link the C++ -library functions. Alternatively, you can run <command>c++</command> -instead of <command>cc</command>, which does this for you. -<command>c++</command> can also be invoked as <command>g++</command> -on FreeBSD.</para> - -<informalexample> -<screen>$ <userinput>cc -o foobar foobar.cc -lg++</userinput> <lineannotation>For FreeBSD 2.1.6 and earlier</> -$ <userinput>cc -o foobar foobar.cc -lstdc++</userinput> <lineannotation>For FreeBSD 2.2 and later</> -$ <userinput>c++ -o foobar foobar.cc</userinput></screen> -</informalexample> - -<para>Each of these will both produce an executable -<filename>foobar</filename> from the C++ source file -<filename>foobar.cc</filename>. Note that, on Unix systems, C++ -source files traditionally end in <filename>.C</filename>, -<filename>.cxx</filename> or <filename>.cc</filename>, rather than -the <trademark>MS-DOS</trademark> style <filename>.cpp</filename> -(which was already used for something else). <command>gcc</command> -used to rely on this to work out what kind of compiler to use on the -source file; however, this restriction no longer applies, so you may -now call your C++ files <filename>.cpp</filename> with -impunity!</para> - -</listitem> -</varlistentry> -</variablelist> - -<sect1> -<title>Common <command>cc</command> Queries and Problems</title> - -<para>Q. I am trying to write a program which uses the -<function>sin()</function> function and I get an error like this. -What does it mean? -<informalexample> -<screen>/var/tmp/cc0143941.o: Undefined symbol `_sin' referenced from text segment</screen> -</informalexample> -</para> - -<para>A. When using mathematical functions like -<function>sin()</function>, you have to tell <command>cc</command> to -link in the math library, like so: -<informalexample> -<screen>$ <userinput>cc -o foobar foobar.c -lm</userinput></screen> -</informalexample></para> - -<para>Q. All right, I wrote this simple program to practice using -<option>-lm</option>. All it does is raise 2.1 to the power of 6. -<informalexample> -<programlisting>#include <stdio.h> - -int main() { - float f; - - f = pow(2.1, 6); - printf("2.1 ^ 6 = %f\n", f); - return 0; -}</programlisting> -</informalexample> -and I compiled it as: -<informalexample> -<screen>$ <userinput>cc temp.c -lm</userinput></screen> -</informalexample> -like you said I should, but I get this when I run it: -<informalexample> -<screen>$ <userinput>./a.out</userinput> -2.1 ^ 6 = 1023.000000</screen> -</informalexample> -</para> - -<para>This is <emphasis>not</emphasis> the right answer! What is -going on?</para> - -<para>A. When the compiler sees you call a function, it checks if it -has already seen a prototype for it. If it has not, it assumes the -function returns an <type>int</type>, which is -definitely not what you want here.</para> - -<para>Q. So how do I fix this?</para> - -<para>A. The prototypes for the mathematical functions are in -<filename>math.h</filename>. If you include this file, the compiler -will be able to find the prototype and it will stop doing strange -things to your calculation! -<informalexample> -<programlisting>#include <math.h> -#include <stdio.h> - -int main() { -...</programlisting> -</informalexample> -</para> - -<para>After recompiling it as you did before, run it: -<informalexample> -<screen>$ <userinput>./a.out</userinput> -2.1 ^ 6 = 85.766121</screen> -</informalexample> -</para> - -<para>If you are using any of the mathematical functions, -<emphasis>always</emphasis> include <filename>math.h</filename> and -remember to link in the math library.</para> - -<para>Q. I compiled a file called <filename>foobar.c</filename> and I -cannot find an executable called <filename>foobar</filename>. Where's -it gone?</para> - -<para>A. Remember, <command>cc</command> will call the executable -<filename>a.out</filename> unless you tell it differently. Use the -<option>-o <replaceable>filename</replaceable></option> option: -<informalexample> -<screen>$ <userinput>cc -o foobar foobar.c</userinput></screen> -</informalexample> -</para> - -<para>Q. OK, I have an executable called <filename>foobar</filename>, -I can see it when I run <command>ls</command>, but when I type in -<command>foobar</command> at the command prompt it tells me there is -no such file. Why can it not find it?</para> - -<para>A. Unlike <trademark>MS-DOS</trademark>, Unix does not look in the -current directory when it is trying to find out which executable you -want it to run, unless you tell it to. Either type -<command>./foobar</command>, which means <quote>run the file called -<filename>foobar</filename> in the current directory</quote>, or -change your <systemitem class=environvar>PATH</systemitem> -environment variable so that it looks something like -<informalexample> -<screen>bin:/usr/bin:/usr/local/bin:.</screen> -</informalexample> -The dot at the end means <quote>look in the current directory if it is not in -any of the others</quote>.</para> - -<para>Q. I called my executable <filename>test</filename>, but -nothing happens when I run it. What is going on?</para> - -<para>A. Most Unix systems have a program called -<command>test</command> in <filename>/usr/bin</filename> and the -shell is picking that one up before it gets to checking the current -directory. Either type: -<informalexample> -<screen>$ <userinput>./test</userinput></screen> -</informalexample> -or choose a better name for your program!</para> - -<para>Q. I compiled my program and it seemed to run all right at -first, then there was an error and it said something about <errorname>core -dumped</errorname>. What does that mean?</para> - -<para>A. The name <firstterm>core dump</firstterm> dates back to the -very early days of Unix, when the machines used core memory for -storing data. Basically, if the program failed under certain -conditions, the system would write the contents of core memory to -disk in a file called <filename>core</filename>, which the programmer -could then pore over to find out what went wrong.</para> - -<para>Q. Fascinating stuff, but what I am supposed to do now?</para> - -<para>A. Use <command>gdb</command> to analyse the core (see <xref -linkend="debugging">).</para> - -<para>Q. When my program dumped core, it said something about a -<errorname>segmentation fault</errorname>. What's that?</para> - -<para>A. This basically means that your program tried to perform some sort -of illegal operation on memory; Unix is designed to protect the -operating system and other programs from rogue programs.</para> - -<para>Common causes for this are: -<itemizedlist> -<listitem><para>Trying to write to a <symbol>NULL</symbol> pointer, eg -<programlisting>char *foo = NULL; -strcpy(foo, "bang!");</programlisting> -</para></listitem> - -<listitem><para>Using a pointer that hasn't been initialised, eg -<programlisting>char *foo; -strcpy(foo, "bang!");</programlisting> -The pointer will have some random value that, with luck, -will point into an area of memory that isn't available to -your program and the kernel will kill your program before -it can do any damage. If you're unlucky, it'll point -somewhere inside your own program and corrupt one of your -data structures, causing the program to fail -mysteriously.</para></listitem> - -<listitem><para>Trying to access past the end of an array, eg -<programlisting>int bar[20]; -bar[27] = 6;</programlisting></para></listitem> - -<listitem><para> Trying to store something in read-only memory, eg -<programlisting>char *foo = "My string"; -strcpy(foo, "bang!");</programlisting> -Unix compilers often put string literals like -<literal>"My string"</literal> into -read-only areas of memory.</para></listitem> - -<listitem><para>Doing naughty things with -<function>malloc()</function> and <function>free()</function>, eg -<programlisting>char bar[80]; -free(bar);</programlisting> -or -<programlisting>char *foo = malloc(27); -free(foo); -free(foo);</programlisting> -</para></listitem> - -</itemizedlist></para> - -<para>Making one of these mistakes will not always lead to an -error, but they are always bad practice. Some systems and -compilers are more tolerant than others, which is why programs -that ran well on one system can crash when you try them on an -another.</para> - -<para>Q. Sometimes when I get a core dump it says <errorname>bus -error</errorname>. It says in my Unix book that this means a hardware -problem, but the computer still seems to be working. Is this -true?</para> - -<para>A. No, fortunately not (unless of course you really do have a hardware -problem…). This is usually another way of saying that you -accessed memory in a way you shouldn't have.</para> - -<para>Q. This dumping core business sounds as though it could be quite -useful, if I can make it happen when I want to. Can I do this, or -do I have to wait until there's an error?</para> - -<para>A. Yes, just go to another console or xterm, do -<screen>$ <userinput>ps</userinput></screen> -to find out the process ID of your program, and do -<screen>$ <userinput>kill -ABRT <replaceable>pid</replaceable></userinput></screen> -where <parameter><replaceable>pid</replaceable></parameter> is the -process ID you looked up.</para> - -<para>This is useful if your program has got stuck in an infinite -loop, for instance. If your program happens to trap -<symbol>SIGABRT</symbol>, there are several other signals which have -a similar effect.</para> - -</sect1> -</chapter> - - -<chapter> -<title>Make</title> - -<sect1> -<title>What is <command>make</command>?</title> - -<para>When you're working on a simple program with only one or two source -files, typing in -<screen>$ <userinput>cc file1.c file2.c</userinput></screen> -is not too bad, but it quickly becomes very tedious when there are -several files—and it can take a while to compile, too.</para> - -<para>One way to get around this is to use object files and only recompile -the source file if the source code has changed. So we could have -something like: -<screen>$ <userinput>cc file1.o file2.o</userinput> … <userinput>file37.c</userinput> &hellip</screen> -if we'd changed <filename>file37.c</filename>, but not any of the -others, since the last time we compiled. This may speed up the -compilation quite a bit, but doesn't solve the typing -problem.</para> - -<para>Or we could write a shell script to solve the typing problem, but it -would have to re-compile everything, making it very inefficient on a -large project.</para> - -<para>What happens if we have hundreds of source files lying about? What if -we're working in a team with other people who forget to tell us when -they've changed one of their source files that we use?</para> - -<para>Perhaps we could put the two solutions together and write something -like a shell script that would contain some kind of magic rule saying -when a source file needs compiling. Now all we need now is a program -that can understand these rules, as it's a bit too complicated for the -shell.</para> - -<para>This program is called <command>make</command>. It reads in a -file, called a <firstterm>makefile</firstterm>, that tells it how -different files depend on each other, and works out which files need -to be re-compiled and which ones don't. For example, a rule could say -something like <quote>if <filename>fromboz.o</filename> is older than -<filename>fromboz.c</filename>, that means someone must have changed -<filename>fromboz.c</filename>, so it needs to be -re-compiled.</quote> The makefile also has rules telling make -<emphasis>how</emphasis> to re-compile the source file, making it a -much more powerful tool.</para> - -<para>Makefiles are typically kept in the same directory as the -source they apply to, and can be called -<filename>makefile</filename>, <filename>Makefile</filename> or -<filename>MAKEFILE</filename>. Most programmers use the name -<filename>Makefile</filename>, as this puts it near the top of a -directory listing, where it can easily be seen.<footnote><para>They -don't use the <filename>MAKEFILE</filename> form as block capitals -are often used for documentation files like -<filename>README</filename>.</para></footnote></para> - -</sect1> - -<sect1> -<title>Example of using <command>make</command></title> - -<para>Here's a very simple make file: -<programlisting>foo: foo.c - cc -o foo foo.c</programlisting> -It consists of two lines, a dependency line and a creation line.</para> - -<para>The dependency line here consists of the name of the program -(known as the <firstterm>target</firstterm>), followed by a colon, -then whitespace, then the name of the source file. When -<command>make</command> reads this line, it looks to see if -<filename>foo</filename> exists; if it exists, it compares the time -<filename>foo</filename> was last modified to the time -<filename>foo.c</filename> was last modified. If -<filename>foo</filename> does not exist, or is older than -<filename>foo.c</filename>, it then looks at the creation line to -find out what to do. In other words, this is the rule for working out -when <filename>foo.c</filename> needs to be re-compiled.</para> - -<para>The creation line starts with a <token>tab</token> (press the -<keycap>tab</keycap> key) and then the command you would type to -create <filename>foo</filename> if you were doing it at a command -prompt. If <filename>foo</filename> is out of date, or does not -exist, <command>make</command> then executes this command to create -it. In other words, this is the rule which tells make how to -re-compile <filename>foo.c</filename>.</para> - -<para>So, when you type <userinput>make</userinput>, it will make -sure that <filename>foo</filename> is up to date with respect to your -latest changes to <filename>foo.c</filename>. This principle can be -extended to <filename>Makefile</filename>s with hundreds of -targets—in fact, on FreeBSD, it is possible to compile the -entire operating system just by typing <userinput>make -world</userinput> in the appropriate directory!</para> - -<para>Another useful property of makefiles is that the targets don't have -to be programs. For instance, we could have a make file that looks -like this: -<programlisting>foo: foo.c - cc -o foo foo.c - -install: - cp foo /home/me</programlisting></para> - -<para>We can tell make which target we want to make by typing: -<screen>$ <userinput>make <replaceable>target</replaceable></userinput></screen> -<command>make</command> will then only look at that target and ignore any -others. For example, if we type <userinput>make foo</userinput> with the -makefile above, make will ignore the <action>install</action> target.</para> - -<para>If we just type <userinput>make</userinput> on its own, make -will always look at the first target and then stop without looking at -any others. So if we typed <userinput>make</userinput> here, it will -just go to the <action>foo</action> target, re-compile -<filename>foo</filename> if necessary, and then stop without going on -to the <action>install</action> target.</para> - -<para>Notice that the <action>install</action> target doesn't -actually depend on anything! This means that the command on the -following line is always executed when we try to make that target by -typing <userinput>make install</userinput>. In this case, it will -copy <filename>foo</filename> into the user's home directory. This is -often used by application makefiles, so that the application can be -installed in the correct directory when it has been correctly -compiled.</para> - -<para>This is a slightly confusing subject to try and explain. If you -don't quite understand how <command>make</command> works, the best -thing to do is to write a simple program like <quote>hello -world</quote> and a make file like the one above and experiment. Then -progress to using more than one source file, or having the source -file include a header file. The <command>touch</command> command is -very useful here—it changes the date on a file without you -having to edit it.</para> - -</sect1> - -<sect1> -<title>FreeBSD Makefiles</title> - -<para>Makefiles can be rather complicated to write. Fortunately, -BSD-based systems like FreeBSD come with some very powerful ones as -part of the system. One very good example of this is the FreeBSD -ports system. Here's the essential part of a typical ports -<filename>Makefile</filename>: -<programlisting>MASTER_SITES= ftp://freefall.cdrom.com/pub/FreeBSD/LOCAL_PORTS/ -DISTFILES= scheme-microcode+dist-7.3-freebsd.tgz - -.include <bsd.port.mk></programlisting></para> - -<para>Now, if we go to the directory for this port and type -<userinput>make</userinput>, the following happens:</para> - -<procedure> -<step><para>A check is made to see if the source code for this port is -already on the system.</para></step> - -<step><para>If it isn't, an FTP connection to the URL in -<symbol>MASTER_SITES</symbol> is set up to download the -source.</para></step> - -<step><para>The checksum for the source is calculated and compared it with -one for a known, good, copy of the source. This is to make sure that -the source was not corrupted while in transit.</para></step> - -<step><para>Any changes required to make the source work on FreeBSD are -applied—this is known as <firstterm>patching</firstterm>.</para></step> - -<step><para>Any special configuration needed for the source is done. -(Many Unix program distributions try to work out which version of -Unix they are being compiled on and which optional Unix features are -present—this is where they are given the information in the -FreeBSD ports scenario).</para></step> - -<step><para>The source code for the program is compiled. In effect, -we change to the directory where the source was unpacked and do -<command>make</command>—the program's own make file has the -necessary information to build the program.</para></step> - -<step><para>We now have a compiled version of the program. If we -wish, we can test it now; when we feel confident about the program, -we can type <userinput>make install</userinput>. This will cause the -program and any supporting files it needs to be copied into the -correct location; an entry is also made into a <database>package -database</database>, so that the port can easily be uninstalled later -if we change our mind about it.</para></step> - -</procedure> - -<para>Now I think you'll agree that's rather impressive for a four -line script!</para> - -<para>The secret lies in the last line, which tells -<command>make</command> to look in the system makefile called -<filename>bsd.port.mk</filename>. It's easy to overlook this line, -but this is where all the clever stuff comes from—someone has -written a makefile that tells <command>make</command> to do all the -things above (plus a couple of other things I didn't mention, -including handling any errors that may occur) and anyone can get -access to that just by putting a single line in their own make -file!</para> - -<para>If you want to have a look at these system makefiles, they're -in <filename>/usr/share/mk</filename>, but it's probably best to wait -until you've had a bit of practice with makefiles, as they are very -complicated (and if you do look at them, make sure you have a flask -of strong coffee handy!)</para> - -</sect1> - -<sect1> -<title>More advanced uses of <command>make</command></title> - -<para><command>Make</command> is a very powerful tool, and can do much -more than the simple example above shows. Unfortunately, there are -several different versions of <command>make</command>, and they all -differ considerably. The best way to learn what they can do is -probably to read the documentation—hopefully this introduction will -have given you a base from which you can do this.</para> - -<para>The version of make that comes with FreeBSD is the <application>Berkeley -make</application>; there is a tutorial for it in -<filename>/usr/share/doc/psd/12.make</filename>. To view it, do -<screen>$ <userinput>zmore paper.ascii.gz</userinput></screen> -in that directory.</para> - -<para>Many applications in the ports use <application>GNU -make</application>, which has a very good set of <quote>info</quote> -pages. If you have installed any of these ports, <application>GNU -make</application> will automatically have been installed as -<command>gmake</command>. It's also available as a port and package -in its own right.</para> - -<para>To view the info pages for <application>GNU make</application>, -you will have to edit the <filename>dir</filename> file in the -<filename>/usr/local/info</filename> directory to add an entry for -it. This involves adding a line like -<programlisting> * Make: (make). The GNU Make utility.</programlisting> -to the file. Once you have done this, you can type -<userinput>info</userinput> and then select -<guimenuitem>make</guimenuitem> from the menu (or in -<application>Emacs</application>, do <userinput>C-h -i</userinput>).</para> - -</sect1> -</chapter> - -<chapter id="debugging"> -<title>Debugging</title> - -<sect1> -<title>The Debugger</title> - -<para>The debugger that comes with FreeBSD is called -<command>gdb</command> (<application>GNU -debugger</application>). You start it up by typing -<screen>$ <userinput>gdb <replaceable>progname</replaceable></userinput></screen> -although most people prefer to run it inside -<application>Emacs</application>. You can do this by: -<screen><userinput>M-x gdb RET <replaceable>progname</replaceable> RET</userinput></screen></para> - -<para>Using a debugger allows you to run the program under more -controlled circumstances. Typically, you can step through the program -a line at a time, inspect the value of variables, change them, tell -the debugger to run up to a certain point and then stop, and so on. -You can even attach to a program that's already running, or load a -core file to investigate why the program crashed. It's even possible -to debug the kernel, though that's a little trickier than the user -applications we'll be discussing in this section.</para> - -<para><command>gdb</command> has quite good on-line help, as well as -a set of info pages, so this section will concentrate on a few of the -basic commands.</para> - -<para>Finally, if you find its text-based command-prompt style -off-putting, there's a graphical front-end for it <ulink -URL="../../ports/devel.html">xxgdb</ulink> -in the ports collection.</para> - -<para>This section is intended to be an introduction to using -<command>gdb</command> and does not cover specialised topics such as -debugging the kernel.</para> - -</sect1> - -<sect1> -<title>Running a program in the debugger</title> - -<para>You'll need to have compiled the program with the -<option>-g</option> option to get the most out of using -<command>gdb</command>. It will work without, but you'll only see the -name of the function you're in, instead of the source code. If you -see a line like: -<screen>… (no debugging symbols found) …</screen>when -<command>gdb</command> starts up, you'll know that the program wasn't -compiled with the <option>-g</option> option.</para> - -<para>At the <command>gdb</command> prompt, type <userinput>break -main</userinput>. This will tell the debugger to skip over the -preliminary set-up code in the program and start at the beginning of -your code. Now type <userinput>run</userinput> to start the -program—it will start at the beginning of the set-up code and -then get stopped by the debugger when it calls -<function>main()</function>. (If you've ever wondered where -<function>main()</function> gets called from, now you know!).</para> - -<para>You can now step through the program, a line at a time, by -pressing <command>n</command>. If you get to a function call, you can -step into it by pressing <command>s</command>. Once you're in a -function call, you can return from stepping into a function call by -pressing <command>f</command>. You can also use <command>up</command> and -<command>down</command> to take a quick look at the caller.</para> - -<para>Here's a simple example of how to spot a mistake in a program -with <command>gdb</command>. This is our program (with a deliberate -mistake): -<programlisting>#include <stdio.h> - -int bazz(int anint); - -main() { - int i; - - printf("This is my program\n"); - bazz(i); - return 0; -} - -int bazz(int anint) { - printf("You gave me %d\n", anint); - return anint; -}</programlisting> -</para> - -<para>This program sets <symbol>i</symbol> to be <literal>5</literal> -and passes it to a function <function>bazz()</function> which prints -out the number we gave it.</para> - -<para>When we compile and run the program we get -<screen>$ <userinput>cc -g -o temp temp.c</userinput> -$ <userinput>./temp</userinput> -This is my program -anint = 4231</screen></para> - -<para>That wasn't what we expected! Time to see what's going -on!<screen>$ <userinput>gdb temp</userinput> -GDB is free software and you are welcome to distribute copies of it - under certain conditions; type "show copying" to see the conditions. -There is absolutely no warranty for GDB; type "show warranty" for details. -GDB 4.13 (i386-unknown-freebsd), Copyright 1994 Free Software Foundation, Inc. -(gdb) <userinput>break main</> <lineannotation>Skip the set-up code</> -Breakpoint 1 at 0x160f: file temp.c, line 9. <lineannotation><command>gdb</command> puts breakpoint at <function>main()</></> -(gdb) <userinput>run</> <lineannotation>Run as far as <function>main()</></> -Starting program: /home/james/tmp/temp <lineannotation>Program starts running</> - -Breakpoint 1, main () at temp.c:9 <lineannotation><command>gdb</command> stops at <function>main()</></> -(gdb) <userinput>n</> <lineannotation>Go to next line</> -This is my program <lineannotation>Program prints out</> -(gdb) <userinput>s</> <lineannotation>step into <function>bazz()</></> -bazz (anint=4231) at temp.c:17 <lineannotation><command>gdb</command> displays stack frame</> -(gdb)</screen></para> - - -<para>Hang on a minute! How did <symbol>anint</symbol> get to be -<literal>4231</literal>? Didn't we set it to be <literal>5</literal> -in <function>main()</function>? Let's move up to -<function>main()</function> and have a look.</para> - -<para><screen>(gdb) <userinput>up</> <lineannotation>Move up call stack</> -#1 0x1625 in main () at temp.c:11 <lineannotation><command>gdb</command> displays stack frame</> -(gdb) <userinput>p i</> <lineannotation>Show us the value of <symbol>i</></> -$1 = 4231 <lineannotation><command>gdb</command> displays <literal>4231</></></screen> -Oh dear! Looking at the code, we forgot to initialise -<symbol>i</symbol>. We meant to put -<programlisting><lineannotation>…</> -main() { - int i; - - i = 5; - printf("This is my program\n"); -<lineannotation>&hellip</></programlisting> -but we left the <literal>i=5;</literal> line out. As we didn't -initialise <symbol>i</symbol>, it had whatever number happened to be -in that area of memory when the program ran, which in this case -happened to be <literal>4231</literal>.</para> - -<note><para><command>gdb</command> displays the stack frame -every time we go into or out of a function, even if we're using -<command>up</command> and <command>down</command> to move around the -call stack. This shows the name of the function and the values of -its arguments, which helps us keep track of where we are and what's -going on. (The stack is a storage area where the program stores -information about the arguments passed to functions and where to go -when it returns from a function call).</para></note> - -</sect1> - -<sect1> -<title>Examining a core file</title> - -<para>A core file is basically a file which contains the complete -state of the process when it crashed. In <quote>the good old -days</quote>, programmers had to print out hex listings of core files -and sweat over machine code manuals, but now life is a bit easier. -Incidentally, under FreeBSD and other 4.4BSD systems, a core file is -called <filename><replaceable>progname</>.core</> instead of just -<filename>core</filename>, to make it clearer which program a core -file belongs to.</para> - -<para>To examine a core file, start up <command>gdb</command> in the -usual way. Instead of typing <command>break</command> or -<command>run</command>, type -<screen>(gdb) <userinput>core <replaceable>progname</replaceable>.core</userinput></screen> -If you're not in the same directory as the core file, you'll have to -do <userinput>dir /path/to/core/file</userinput> first.</para> - -<para>You should see something like this: -<screen>$ <userinput>gdb a.out</userinput> -GDB is free software and you are welcome to distribute copies of it - under certain conditions; type "show copying" to see the conditions. -There is absolutely no warranty for GDB; type "show warranty" for details. -GDB 4.13 (i386-unknown-freebsd), Copyright 1994 Free Software Foundation, Inc. -(gdb) <userinput>core a.out.core</userinput> -Core was generated by `a.out'. -Program terminated with signal 11, Segmentation fault. -Cannot access memory at address 0x7020796d. -#0 0x164a in bazz (anint=0x5) at temp.c:17 -(gdb)</screen></para> - -<para>In this case, the program was called -<filename>a.out</filename>, so the core file is called -<filename>a.out.core</filename>. We can see that the program crashed -due to trying to access an area in memory that was not available to -it in a function called <function>bazz</function>.</para> - -<para>Sometimes it's useful to be able to see how a function was -called, as the problem could have occurred a long way up the call -stack in a complex program. The <command>bt</command> command causes -<command>gdb</command> to print out a back-trace of the call -stack: -<screen>(gdb) <userinput>bt</userinput> -#0 0x164a in bazz (anint=0x5) at temp.c:17 -#1 0xefbfd888 in end () -#2 0x162c in main () at temp.c:11 -(gdb)</screen>The <function>end()</function> function is called when -a program crashes; in this case, the <function>bazz()</function> -function was called from <function>main()</function>.</para> - -</sect1> - -<sect1> -<title>Attaching to a running program</title> - -<para>One of the neatest features about <command>gdb</command> is -that it can attach to a program that's already running. Of course, -that assumes you have sufficient permissions to do so. A common -problem is when you are stepping through a program that forks, and -you want to trace the child, but the debugger will only let you trace -the parent.</para> - -<para>What you do is start up another <command>gdb</command>, use -<command>ps</command> to find the process ID for the child, and -do<screen>(gdb) <userinput>attach <replaceable>pid</replaceable></userinput></screen> -in <command>gdb</command>, and then debug as usual.</para> - -<para><quote>That's all very well,</quote> you're probably thinking, -<quote>but by the time I've done that, the child process will be over -the hill and far away</quote>. Fear not, gentle reader, here's how to -do it (courtesy of the <command>gdb</command> info pages): -<screen><lineannotation>&hellip</lineannotation> -if ((pid = fork()) < 0) /* _Always_ check this */ - error(); -else if (pid == 0) { /* child */ - int PauseMode = 1; - - while (PauseMode) - sleep(10); /* Wait until someone attaches to us */ - <lineannotation>&hellip</lineannotation> -} else { /* parent */ - <lineannotation>&hellip</lineannotation></screen> -Now all you have to do is attach to the child, set -<symbol>PauseMode</symbol> to <literal>0</literal>, and -wait for the <function>sleep()</function> call to return!</para> - -</sect1> -</chapter> - -<chapter id="emacs"> -<title>Using Emacs as a Development Environment</title> - -<sect1> -<title>Emacs</title> - -<para>Unfortunately, Unix systems don't come with the kind of -everything-you-ever-wanted-and-lots-more-you-didn't-in-one-gigantic-package -integrated development environments that other systems -have.<footnote><para>At least, not unless you pay out very large sums -of money.</para></footnote> However, it is possible to set up your -own environment. It may not be as pretty, and it may not be quite as -integrated, but you can set it up the way you want it. And it's free. -And you have the source to it.</para> - -<para>The key to it all is Emacs. Now there are some people who -loathe it, but many who love it. If you're one of the former, I'm -afraid this section will hold little of interest to you. Also, you'll -need a fair amount of memory to run it—I'd recommend 8MB in -text mode and 16MB in X as the bare minimum to get reasonable -performance.</para> - -<para>Emacs is basically a highly customisable editor—indeed, -it has been customised to the point where it's more like an operating -system than an editor! Many developers and sysadmins do in fact -spend practically all their time working inside Emacs, leaving it -only to log out.</para> - -<para>It's impossible even to summarise everything Emacs can do here, but -here are some of the features of interest to developers: -<itemizedlist> - -<listitem><para>Very powerful editor, allowing search-and-replace on -both strings and regular expressions (patterns), jumping to start/end -of block expression, etc, etc.</para></listitem> - -<listitem><para>Pull-down menus and online help.</para></listitem> - -<listitem><para>Language-dependent syntax highlighting and -indentation.</para></listitem> - -<listitem><para>Completely customisable.</para></listitem> - -<listitem><para>You can compile and debug programs within -Emacs.</para></listitem> - -<listitem><para>On a compilation error, you can jump to the offending -line of source code.</para></listitem> - -<listitem><para>Friendly-ish front-end to the <command>info</command> -program used for reading GNU hypertext documentation, including the -documentation on Emacs itself.</para></listitem> - -<listitem><para>Friendly front-end to <command>gdb</command>, -allowing you to look at the source code as you step through your -program.</para></listitem> - -<listitem><para>You can read Usenet news and mail while your program -is compiling.</para></listitem> - -</itemizedlist>And doubtless many more that I've overlooked.</para> - -<para>Emacs can be installed on FreeBSD using <ulink -URL="../../ports/editors.html">the Emacs -port</ulink>.</para> - -<para>Once it's installed, start it up and do <userinput>C-h -t</userinput> to read an Emacs tutorial—that means hold down -the <keycap>control</keycap> key, press <keycap>h</keycap>, let go of -the <keycap>control</keycap> key, and then press <keycap>t</keycap>. -(Alternatively, you can you use the mouse to select <guimenuitem>Emacs -Tutorial</guimenuitem> from the <guimenu>Help</guimenu> menu).</para> - -<para>Although Emacs does have menus, it's well worth learning the -key bindings, as it's much quicker when you're editing something to -press a couple of keys than to try and find the mouse and then click -on the right place. And, when you're talking to seasoned Emacs users, -you'll find they often casually throw around expressions like -<quote><literal>M-x replace-s RET foo RET bar RET</literal></quote> -so it's useful to know what they mean. And in any case, Emacs has far -too many useful functions for them to all fit on the menu -bars.</para> - -<para>Fortunately, it's quite easy to pick up the key-bindings, as -they're displayed next to the menu item. My advice is to use the -menu item for, say, opening a file until you understand how it works -and feel confident with it, then try doing C-x C-f. When you're happy -with that, move on to another menu command.</para> - -<para>If you can't remember what a particular combination of keys -does, select <guimenuitem>Describe Key</guimenuitem> from the -<guimenu>Help</guimenu> menu and type it in—Emacs will tell you -what it does. You can also use the <guimenuitem>Command -Apropos</guimenuitem> menu item to find out all the commands which -contain a particular word in them, with the key binding next to -it.</para> - -<para>By the way, the expression above means hold down the -<keysym>Meta</keysym> key, press <keysym>x</keysym>, release the -<keysym>Meta</keysym> key, type <userinput>replace-s</userinput> -(short for <literal>replace-string</literal>—another feature of -Emacs is that you can abbreviate commands), press the -<keysym>return</keysym> key, type <userinput>foo</userinput> (the -string you want replaced), press the <keysym>return</keysym> key, -type bar (the string you want to replace <literal>foo</literal> with) -and press <keysym>return</keysym> again. Emacs will then do the -search-and-replace operation you've just requested.</para> - -<para>If you're wondering what on earth the <keysym>Meta</keysym> key -is, it's a special key that many Unix workstations have. -Unfortunately, PC's don't have one, so it's usually the -<keycap>alt</keycap> key (or if you're unlucky, the <keysym>escape</keysym> -key).</para> - -<para>Oh, and to get out of Emacs, do <command>C-x C-c</command> -(that means hold down the <keysym>control</keysym> key, press -<keysym>c</keysym>, press <keysym>x</keysym> and release the -<keysym>control</keysym> key). If you have any unsaved files open, -Emacs will ask you if you want to save them. (Ignore the bit in the -documentation where it says <command>C-z</command> is the usual way -to leave Emacs—that leaves Emacs hanging around in the -background, and is only really useful if you're on a system which -doesn't have virtual terminals).</para> - -</sect1> - -<sect1> -<title>Configuring Emacs</title> - -<para>Emacs does many wonderful things; some of them are built in, -some of them need to be configured.</para> - -<para>Instead of using a proprietary macro language for -configuration, Emacs uses a version of Lisp specially adapted for -editors, known as Emacs Lisp. This can be quite useful if you want to -go on and learn something like Common Lisp, as it's considerably -smaller than Common Lisp (although still quite big!).</para> - -<para>The best way to learn Emacs Lisp is to download the <ulink -URL="ftp://prep.ai.mit.edu:pub/gnu/elisp-manual-19-2.4.tar.gz">Emacs -Tutorial</ulink></para> - -<para>However, there's no need to actually know any Lisp to get -started with configuring Emacs, as I've included a sample -<filename>.emacs</filename> file, which should be enough to get you -started. Just copy it into your home directory and restart Emacs if -it's already running; it will read the commands from the file and -(hopefully) give you a useful basic setup.</para> - -</sect1> - -<sect1> -<title>A sample <filename>.emacs</filename> file</title> - -<para>Unfortunately, there's far too much here to explain it in detail; -however there are one or two points worth mentioning.</para> - -<para> -<itemizedlist> - -<listitem><para>Everything beginning with a <literal>;</> is a -comment and is ignored by Emacs.</para></listitem> - -<listitem><para>In the first line, the -<literal>-*- Emacs-Lisp -*-</literal> is so that we can -edit the <filename>.emacs</filename> file itself within Emacs and get -all the fancy features for editing Emacs Lisp. Emacs usually tries to -guess this based on the filename, and may not get it right for -<filename>.emacs</filename>. </para></listitem> - -<listitem><para>The <keysym>tab</keysym> key is bound to an -indentation function in some modes, so when you press the tab key, it -will indent the current line of code. If you want to put a -<token>tab</token> character in whatever you're writing, hold the -<keysym>control</keysym> key down while you're pressing the -<keysym>tab</keysym> key.</para></listitem> - -<listitem><para>This file supports syntax highlighting for C, C++, -Perl, Lisp and Scheme, by guessing the language from the -filename.</para></listitem> - -<listitem><para>Emacs already has a pre-defined function called -<function>next-error</function>. In a compilation output window, this -allows you to move from one compilation error to the next by doing -<command>M-n</command>; we define a complementary function, -<function>previous-error</function>, that allows you to go to a -previous error by doing <command>M-p</command>. The nicest feature of -all is that <command>C-c C-c</command> will open up the source file -in which the error occurred and jump to the appropriate -line.</para></listitem> - -<listitem><para> We enable Emacs's ability to act as a server, so -that if you're doing something outside Emacs and you want to edit a -file, you can just type in -<screen>$ <userinput>emacsclient <replaceable>filename</replaceable></userinput></screen> -and then you can edit the file in your Emacs!<footnote><para>Many -Emacs users set their <systemitem -class=environvar>EDITOR</systemitem> environment to -<literal>emacsclient</literal> so this happens every time they need -to edit a file.</para></footnote></para></listitem> - -</itemizedlist> -</para> - -<example> -<title>A sample <filename>.emacs</filename> file</title> -<screen>;; -*-Emacs-Lisp-*- - -;; This file is designed to be re-evaled; use the variable first-time -;; to avoid any problems with this. -(defvar first-time t - "Flag signifying this is the first time that .emacs has been evaled") - -;; Meta -(global-set-key "\M- " 'set-mark-command) -(global-set-key "\M-\C-h" 'backward-kill-word) -(global-set-key "\M-\C-r" 'query-replace) -(global-set-key "\M-r" 'replace-string) -(global-set-key "\M-g" 'goto-line) -(global-set-key "\M-h" 'help-command) - -;; Function keys -(global-set-key [f1] 'manual-entry) -(global-set-key [f2] 'info) -(global-set-key [f3] 'repeat-complex-command) -(global-set-key [f4] 'advertised-undo) -(global-set-key [f5] 'eval-current-buffer) -(global-set-key [f6] 'buffer-menu) -(global-set-key [f7] 'other-window) -(global-set-key [f8] 'find-file) -(global-set-key [f9] 'save-buffer) -(global-set-key [f10] 'next-error) -(global-set-key [f11] 'compile) -(global-set-key [f12] 'grep) -(global-set-key [C-f1] 'compile) -(global-set-key [C-f2] 'grep) -(global-set-key [C-f3] 'next-error) -(global-set-key [C-f4] 'previous-error) -(global-set-key [C-f5] 'display-faces) -(global-set-key [C-f8] 'dired) -(global-set-key [C-f10] 'kill-compilation) - -;; Keypad bindings -(global-set-key [up] "\C-p") -(global-set-key [down] "\C-n") -(global-set-key [left] "\C-b") -(global-set-key [right] "\C-f") -(global-set-key [home] "\C-a") -(global-set-key [end] "\C-e") -(global-set-key [prior] "\M-v") -(global-set-key [next] "\C-v") -(global-set-key [C-up] "\M-\C-b") -(global-set-key [C-down] "\M-\C-f") -(global-set-key [C-left] "\M-b") -(global-set-key [C-right] "\M-f") -(global-set-key [C-home] "\M-<") -(global-set-key [C-end] "\M->") -(global-set-key [C-prior] "\M-<") -(global-set-key [C-next] "\M->") - -;; Mouse -(global-set-key [mouse-3] 'imenu) - -;; Misc -(global-set-key [C-tab] "\C-q\t") ; Control tab quotes a tab. -(setq backup-by-copying-when-mismatch t) - -;; Treat 'y' or <CR> as yes, 'n' as no. -(fset 'yes-or-no-p 'y-or-n-p) - (define-key query-replace-map [return] 'act) - (define-key query-replace-map [?\C-m] 'act) - -;; Load packages -(require 'desktop) -(require 'tar-mode) - -;; Pretty diff mode -(autoload 'ediff-buffers "ediff" "Intelligent Emacs interface to diff" t) -(autoload 'ediff-files "ediff" "Intelligent Emacs interface to diff" t) -(autoload 'ediff-files-remote "ediff" - "Intelligent Emacs interface to diff") </screen> - -<screen>(if first-time - (setq auto-mode-alist - (append '(("\\.cpp$" . c++-mode) - ("\\.hpp$" . c++-mode) - ("\\.lsp$" . lisp-mode) - ("\\.scm$" . scheme-mode) - ("\\.pl$" . perl-mode) - ) auto-mode-alist))) - -;; Auto font lock mode -(defvar font-lock-auto-mode-list - (list 'c-mode 'c++-mode 'c++-c-mode 'emacs-lisp-mode 'lisp-mode 'perl-mode 'scheme-mode) - "List of modes to always start in font-lock-mode") - -(defvar font-lock-mode-keyword-alist - '((c++-c-mode . c-font-lock-keywords) - (perl-mode . perl-font-lock-keywords)) - "Associations between modes and keywords") - -(defun font-lock-auto-mode-select () - "Automatically select font-lock-mode if the current major mode is -in font-lock-auto-mode-list" - (if (memq major-mode font-lock-auto-mode-list) - (progn - (font-lock-mode t)) - ) - ) - -(global-set-key [M-f1] 'font-lock-fontify-buffer) - -;; New dabbrev stuff -;(require 'new-dabbrev) -(setq dabbrev-always-check-other-buffers t) -(setq dabbrev-abbrev-char-regexp "\\sw\\|\\s_") -(add-hook 'emacs-lisp-mode-hook - '(lambda () - (set (make-local-variable 'dabbrev-case-fold-search) nil) - (set (make-local-variable 'dabbrev-case-replace) nil))) -(add-hook 'c-mode-hook - '(lambda () - (set (make-local-variable 'dabbrev-case-fold-search) nil) - (set (make-local-variable 'dabbrev-case-replace) nil))) -(add-hook 'text-mode-hook - '(lambda () - (set (make-local-variable 'dabbrev-case-fold-search) t) - (set (make-local-variable 'dabbrev-case-replace) t))) - -;; C++ and C mode... -(defun my-c++-mode-hook () - (setq tab-width 4) - (define-key c++-mode-map "\C-m" 'reindent-then-newline-and-indent) - (define-key c++-mode-map "\C-ce" 'c-comment-edit) - (setq c++-auto-hungry-initial-state 'none) - (setq c++-delete-function 'backward-delete-char) - (setq c++-tab-always-indent t) - (setq c-indent-level 4) - (setq c-continued-statement-offset 4) - (setq c++-empty-arglist-indent 4)) - -(defun my-c-mode-hook () - (setq tab-width 4) - (define-key c-mode-map "\C-m" 'reindent-then-newline-and-indent) - (define-key c-mode-map "\C-ce" 'c-comment-edit) - (setq c-auto-hungry-initial-state 'none) - (setq c-delete-function 'backward-delete-char) - (setq c-tab-always-indent t) -;; BSD-ish indentation style - (setq c-indent-level 4) - (setq c-continued-statement-offset 4) - (setq c-brace-offset -4) - (setq c-argdecl-indent 0) - (setq c-label-offset -4)) - -;; Perl mode -(defun my-perl-mode-hook () - (setq tab-width 4) - (define-key c++-mode-map "\C-m" 'reindent-then-newline-and-indent) - (setq perl-indent-level 4) - (setq perl-continued-statement-offset 4)) - -;; Scheme mode... -(defun my-scheme-mode-hook () - (define-key scheme-mode-map "\C-m" 'reindent-then-newline-and-indent)) - -;; Emacs-Lisp mode... -(defun my-lisp-mode-hook () - (define-key lisp-mode-map "\C-m" 'reindent-then-newline-and-indent) - (define-key lisp-mode-map "\C-i" 'lisp-indent-line) - (define-key lisp-mode-map "\C-j" 'eval-print-last-sexp)) - -;; Add all of the hooks... -(add-hook 'c++-mode-hook 'my-c++-mode-hook) -(add-hook 'c-mode-hook 'my-c-mode-hook) -(add-hook 'scheme-mode-hook 'my-scheme-mode-hook) -(add-hook 'emacs-lisp-mode-hook 'my-lisp-mode-hook) -(add-hook 'lisp-mode-hook 'my-lisp-mode-hook) -(add-hook 'perl-mode-hook 'my-perl-mode-hook) - -;; Complement to next-error -(defun previous-error (n) - "Visit previous compilation error message and corresponding source code." - (interactive "p") - (next-error (- n)))</screen> - -<screen>;; Misc... -(transient-mark-mode 1) -(setq mark-even-if-inactive t) -(setq visible-bell nil) -(setq next-line-add-newlines nil) -(setq compile-command "make") -(setq suggest-key-bindings nil) -(put 'eval-expression 'disabled nil) -(put 'narrow-to-region 'disabled nil) -(put 'set-goal-column 'disabled nil) - -;; Elisp archive searching -(autoload 'format-lisp-code-directory "lispdir" nil t) -(autoload 'lisp-dir-apropos "lispdir" nil t) -(autoload 'lisp-dir-retrieve "lispdir" nil t) -(autoload 'lisp-dir-verify "lispdir" nil t) - -;; Font lock mode -(defun my-make-face (face colour &optional bold) - "Create a face from a colour and optionally make it bold" - (make-face face) - (copy-face 'default face) - (set-face-foreground face colour) - (if bold (make-face-bold face)) - ) - -(if (eq window-system 'x) - (progn - (my-make-face 'blue "blue") - (my-make-face 'red "red") - (my-make-face 'green "dark green") - (setq font-lock-comment-face 'blue) - (setq font-lock-string-face 'bold) - (setq font-lock-type-face 'bold) - (setq font-lock-keyword-face 'bold) - (setq font-lock-function-name-face 'red) - (setq font-lock-doc-string-face 'green) - (add-hook 'find-file-hooks 'font-lock-auto-mode-select) - - (setq baud-rate 1000000) - (global-set-key "\C-cmm" 'menu-bar-mode) - (global-set-key "\C-cms" 'scroll-bar-mode) - (global-set-key [backspace] 'backward-delete-char) - ; (global-set-key [delete] 'delete-char) - (standard-display-european t) - (load-library "iso-transl"))) - -;; X11 or PC using direct screen writes -(if window-system - (progn - ;; (global-set-key [M-f1] 'hilit-repaint-command) - ;; (global-set-key [M-f2] [?\C-u M-f1]) - (setq hilit-mode-enable-list - '(not text-mode c-mode c++-mode emacs-lisp-mode lisp-mode - scheme-mode) - hilit-auto-highlight nil - hilit-auto-rehighlight 'visible - hilit-inhibit-hooks nil - hilit-inhibit-rebinding t) - (require 'hilit19) - (require 'paren)) - (setq baud-rate 2400) ; For slow serial connections - ) - -;; TTY type terminal -(if (and (not window-system) - (not (equal system-type 'ms-dos))) - (progn - (if first-time - (progn - (keyboard-translate ?\C-h ?\C-?) - (keyboard-translate ?\C-? ?\C-h))))) - -;; Under UNIX -(if (not (equal system-type 'ms-dos)) - (progn - (if first-time - (server-start)))) - -;; Add any face changes here -(add-hook 'term-setup-hook 'my-term-setup-hook) -(defun my-term-setup-hook () - (if (eq window-system 'pc) - (progn -;; (set-face-background 'default "red") - ))) - -;; Restore the "desktop" - do this as late as possible -(if first-time - (progn - (desktop-load-default) - (desktop-read))) - -;; Indicate that this file has been read at least once -(setq first-time nil) - -;; No need to debug anything now -(setq debug-on-error nil) - -;; All done -(message "All done, %s%s" (user-login-name) ".") -</screen> -</example> - -</sect1> - -<sect1> -<title>Extending the Range of Languages Emacs Understands</title> - -<para>Now, this is all very well if you only want to program in the -languages already catered for in the <filename>.emacs</filename> file -(C, C++, Perl, Lisp and Scheme), but what happens if a new language -called <quote>whizbang</quote> comes out, full of exciting -features?</para> - -<para>The first thing to do is find out if whizbang -comes with any files that tell Emacs about the language. These -usually end in <filename>.el</filename>, short for <quote>Emacs -Lisp</quote>. For example, if whizbang is a FreeBSD -port, we can locate these files by doing -<screen>$ <userinput>find /usr/ports/lang/whizbang -name "*.el" -print</userinput></screen> -and install them by copying them into the Emacs site Lisp directory. On -FreeBSD 2.1.0-RELEASE, this is -<filename>/usr/local/share/emacs/site-lisp</filename>.</para> - -<para>So for example, if the output from the find command was -<screen>/usr/ports/lang/whizbang/work/misc/whizbang.el</screen> -we would do -<screen>$ <userinput>cp /usr/ports/lang/whizbang/work/misc/whizbang.el /usr/local/share/emacs/site-lisp</userinput></screen> -</para> - -<para>Next, we need to decide what extension whizbang source files -have. Let's say for the sake of argument that they all end in -<filename>.wiz</filename>. We need to add an entry to our -<filename>.emacs</filename> file to make sure Emacs will be able to -use the information in <filename>whizbang.el</filename>.</para> - -<para>Find the <symbol>auto-mode-alist entry</symbol> in -<filename>.emacs</filename> and add a line for whizbang, such -as: -<programlisting><lineannotation>…</> -("\\.lsp$" . lisp-mode) -("\\.wiz$" . whizbang-mode) -("\\.scm$" . scheme-mode) -<lineannotation>…</></programlisting> -This means that Emacs will automatically go into -<function>whizbang-mode</function> when you edit a file ending in -<filename>.wiz</filename>.</para> - -<para>Just below this, you'll find the -<symbol>font-lock-auto-mode-list</symbol> entry. Add -<function>whizbang-mode</function> to it like so: -<programlisting>;; Auto font lock mode -(defvar font-lock-auto-mode-list - (list 'c-mode 'c++-mode 'c++-c-mode 'emacs-lisp-mode 'whizbang-mode 'lisp-mode 'perl-mode 'scheme-mode) - "List of modes to always start in font-lock-mode")</programlisting> -This means that Emacs will always enable -<function>font-lock-mode</function> (ie syntax highlighting) when -editing a <filename>.wiz</filename> file.</para> - -<para>And that's all that's needed. If there's anything else you want -done automatically when you open up a <filename>.wiz</filename> file, -you can add a <function>whizbang-mode hook</function> (see -<function>my-scheme-mode-hook</function> for a simple example that -adds <function>auto-indent</function>).</para> - -</sect1> -</chapter> - -<chapter> -<title>Further Reading</title> - -<itemizedlist> -<listitem><para>Brian Harvey and Matthew Wright -<emphasis>Simply Scheme</emphasis> -MIT 1994.<!-- <br> --> -ISBN 0-262-08226-8</para></listitem> - -<listitem><para>Randall Schwartz -<emphasis>Learning Perl</emphasis> -O'Reilly 1993<!-- <br> --> -ISBN 1-56592-042-2</para></listitem> - -<listitem><para>Patrick Henry Winston and Berthold Klaus Paul Horn -<emphasis>Lisp (3rd Edition)</emphasis> -Addison-Wesley 1989<!-- <br> --> -ISBN 0-201-08319-1</para></listitem> - -<listitem><para>Brian W. Kernighan and Rob Pike -<emphasis>The Unix Programming Environment</emphasis> -Prentice-Hall 1984<!-- <br> --> -ISBN 0-13-937681-X</para></listitem> - -<listitem><para>Brian W. Kernighan and Dennis M. Ritchie -<emphasis>The C Programming Language (2nd Edition)</emphasis> -Prentice-Hall 1988<!-- <br> --> -ISBN 0-13-110362-8</para></listitem> - -<listitem><para>Bjarne Stroustrup -<emphasis>The C++ Programming Language</emphasis> -Addison-Wesley 1991<!-- <br> --> -ISBN 0-201-53992-6</para></listitem> - -<listitem><para>W. Richard Stevens -<emphasis>Advanced Programming in the Unix Environment</emphasis> -Addison-Wesley 1992<!-- <br> --> -ISBN 0-201-56317-7</para></listitem> - -<listitem><para>W. Richard Stevens -<emphasis>Unix Network Programming</emphasis> -Prentice-Hall 1990<!-- <br> --> -ISBN 0-13-949876-1</para></listitem> - -</itemizedlist> - -</chapter> -</book> |