diff --git a/zh_TW.Big5/books/developers-handbook/tools/chapter.sgml b/zh_TW.Big5/books/developers-handbook/tools/chapter.sgml index 7508065173..7792645293 100644 --- a/zh_TW.Big5/books/developers-handbook/tools/chapter.sgml +++ b/zh_TW.Big5/books/developers-handbook/tools/chapter.sgml @@ -1,2366 +1,2234 @@ James Raynard Contributed by Murray Stokely - Programming Tools - Synopsis + 程式開發工具 + 概敘 - This chapter 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 - not attempt to describe coding in any - detail. Most of the chapter assumes little or no previous - programming knowledge, although it is hoped that most - programmers will find something of value in it. + + 本章將介紹如何使用一些 FreeBSD 所提供的程式開發工具(programing tools)， + 本章所介紹的工具程式在其他版本的 &unix; 上也可使用， + 在此 並不會 嘗試描述寫程式時的每個細節， + 本章大部分篇幅都是假設你以前沒有或只有少數的寫程式經驗， + 不過，還是希望大多數的程式開發人員都能從中重新得到一些啟發。 + - Introduction - - 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 sed and 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 &posix; and - 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. - - However, all this power can be rather overwhelming at first - if you have 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. - - 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! + 簡介 + + + FreeBSD 提供一個非常棒的開發環境， + 比如說像是 C、C++、Fortran 和 assembler(組合語言)的編譯器(compiler), + 在 FreeBSD 中都已經包含在基本的系統中了 + 更別提 Perl 和其他標準 &unix; 工具，像是sed 以及 awk， + 如果你還是覺得不夠，FreeBSD在 Ports collection 中還提供其他的編譯器和直譯器(interpreter), + FreeBSD 相容許多標準，像是 &posix; 和 ANSI C， + 當然還有它所繼承的 BSD 傳統。 + 所以在 FreeBSD 上寫的程式不需修改或頂多稍微修改，就可以在許多平台上編譯、執行。 + + + + 無論如何，就算你從來沒在 &unix; 平台上寫過程式，也可以徹底感受到FreeBSD 令人無法抗拒的迷人魔力。 + 本章的目標就是協助你快速上手，而暫時不需深入太多進階主題， + 並且講解一些基礎概念，以讓你可以瞭解我們在講些什麼。 + + + + 本章內容並不要求你得有程式開發經驗，或者你只有一點點的經驗而已。 + 不過，我們假設你已經會 &unix; 系統的基本操作， + 而且更重要的是，請保持樂於學習的心態！ + - Introduction to Programming - - 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 - commands as they are usually called. One way - uses an interpreter, the other a - 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. + Programming 概念 + + + 簡單的說，程式只是一堆指令的集合體；而這些指令是用來告訴電腦應該要作那些事情。 + 有時候，指令的執行取決於前一個指令的結果而定。 + 本章將會告訴你有 2 個主要的方法，讓你可以對電腦下達這些指示(instruction) 或 命令(commands)。 + 第一個方法就是 直譯器(interpreter)， + 而第二個方法是 編譯器(compiler)。 + 由於對於電腦而言，人類語言的語意過於模糊而太難理解， + 因此命令(commands)就常會以一種(或多種)程式語言寫成，用來指示電腦所要執行的特定動作為何。 + - Interpreters - - 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. - - 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. - - 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 (sh, csh) is itself an - interpreter, and many people do in fact write shell - scripts to help with various - 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. + 直譯器 + + + 使用直譯器時，所使用的程式語言就像變成一個會和你互動的環境。 + 當在命令提示列上打上命令時，直譯器會即時執行該命令。 + 在比較複雜的程式中，可以把所有想下達的命令統統輸入到某檔案裡面去， + 然後呼叫直譯器去讀取該檔案，並且執行你寫在這個檔案中的指令。 + 如果所下的指令有錯誤產生，大多數的直譯器會進入偵錯模式(debugger)， + 並且顯示相關錯誤訊息，以便對程式除錯。 + + + + 這種方式好處在於：可以立刻看到指令的執行結果，以及錯誤也可迅速修正。 + 相對的，最大的壞處便是當你想把你寫的程式分享給其他人時，這些人必須要有跟你一樣的直譯器。 + 而且別忘了，他們也要會使用直譯器直譯程式才行。 + 當然使用者也不希望不小心按錯鍵，就進入偵錯模式而不知所措。 + 就執行效率而言，直譯器會使用到很多的記憶體， + 而且這類直譯式程式，通常並不會比編譯器所編譯的程式的更有效率。 + + + + 筆者個人認為，如果你之前沒有學過任何程式語言，最好先學學習直譯式語言(interpreted languages)， + 像是 Lisp，Smalltalk，Perl 和 Basic 都是，&unix; 的 shell 像是 sh 和 csh + 它們本身就是直譯器，事實上，很多人都在它們自己機器上撰寫各式的 shell script， + 來順利完成各項 housekeeping(維護) 任務。 + &unix; 使用哲學之一就是提供大量的小工具， + 並使用 shell script 來組合運用這些小工具，以便工作更有效率。 - Interpreters available with FreeBSD + FreeBSD 提供的直譯器 - Here is a list of interpreters that are available from - the &os; Ports Collection, with a brief discussion of - some of the more popular interpreted languages. - - Instructions on how to get and install applications - from the Ports Collection can be found in the - - Ports section of the handbook. + + 下面這邊有份 &os; Ports Collection 所提供的直譯器清單，還有討論一些比較受歡迎的直譯式語言 + + 至於如何使用 Ports Collection 安裝的說明，可參閱 FreeBSD Handbook 中的 + Ports章節。 BASIC - 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, - BASIC has been the first programming - language for many programmers. It is also the foundation - for Visual Basic. - - The Bywater Basic Interpreter can be found in the - Ports Collection as - lang/bwbasic - and the Phil Cockroft's Basic Interpreter - (formerly Rabbit Basic) is available as - lang/pbasic. + BASIC 是 Beginner's ALL-purpose Symbolic Instruction Code 的縮寫。 + BASIC 於 1950 年代開始發展，最初開發這套語言的目的是為了教導當時的大學學生如何寫程式。 + 到了 1980，BASIC已經是很多 programmer 第一個學習的程式語言了。 + 此外，BASIC 也是 Visual Basic 的基礎。 + + FreeBSD Ports Collection 也有收錄相關的 BASIC 直譯器。 + Bywater Basic 直譯器放在 lang/bwbasic。 + 而 Phil Cockroft's Basic 直譯器(早期也叫 Rabbit Basic)放在 lang/pbasic。 Lisp - A language that was developed in the late 1950s as - an alternative to the number-crunching - 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 List Processing. - Very popular in AI (Artificial Intelligence) - circles. - - Lisp is an extremely powerful and sophisticated - language, but can be rather large and unwieldy. - - Various implementations of Lisp that can run on &unix; - systems are available in the Ports Collection for &os;. - GNU Common Lisp can be found as - lang/gcl. CLISP - by Bruno Haible and Michael Stoll is available as - lang/clisp. - For CMUCL, which includes a highly-optimizing compiler too, or - simpler Lisp implementations like SLisp, which implements most - of the Common Lisp constructs in a few hundred lines of C code, - lang/cmucl and - lang/slisp are available - respectively. + LISP 是在 1950 年代開始發展的一個直譯式語言，而且 LISP 就是一種 + number-crunching languages(迅速進行大量運算的程式語言)，在當時算是一個普遍的程式語言。 + LISP 的表達不是基於數字(numbers)，而是基於表(lists)。 + 而最能表示出 LISP 特色的地方就在於： LISP 是 List Processing 的縮寫。 + 在人工智慧(Artificial Intelligence, AI)領域上 LISP 的各式應用非常普遍。 + + LISP 是非常強悍且複雜的程式語言，但是缺點是程式碼會非常大而且難以操作。 + + 絕大部分的 LISP 直譯器都可以在 &unix; 系統上運作，當然 &os; 的 Ports Collection 也有收錄。 + GNU Common Lisp 收錄在 lang/gcl， + Bruno Haible 和 Michael Stoll 的 CLISP 收錄在 lang/clisp + ，此外 CMUCL(包含一個已經最佳化的編譯器)， + 以及其他簡化版的 LISP 直譯器(比如以 C 語言寫的 SLisp，只用幾百行程式碼就實作大多數 Common Lisp 的功能) + 則是分別收錄在 lang/cmucl 以及 + lang/slisp。 + Perl - Very popular with system administrators for writing - scripts; also often used on World Wide Web servers for - writing CGI scripts. - - Perl is available in the Ports Collection as - lang/perl5 for all - &os; releases, and is installed as /usr/bin/perl - in the base system 4.X releases. + 對系統管理者而言，最愛用 perl 來撰寫 scripts 以管理主機， + 同時也經常用來寫 WWW 主機上的 CGI Script 程式。 + + Perl 在 Ports Collection 內的 lang/perl5。 + 而 &os; 4.X 則是把 Perl 裝在 /usr/bin/perl。 Scheme - 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. - - Scheme is available from the Ports Collection as - lang/elk for the - Elk Scheme Interpreter. The MIT Scheme Interpreter - can be found in - lang/mit-scheme - and the SCM Scheme Interpreter in - lang/scm. + Scheme 是 LISP 的另一分支，Scheme 的特點就是比 Common LISP 還要簡潔有力。 + 由於 Scheme 簡單，所以很多大學拿來當作第一堂程式語言教學教材。 + 而且對於研究人員來說也可以快速的開發他們所需要的程式。 + + + Scheme 收錄在 lang/elk， + Elk Scheme 直譯器(由麻省理工學院所發展的 Scheme 直譯器)收錄在 + lang/mit-scheme， + SCM Scheme Interpreter 收錄在 lang/scm。 Icon - Icon is a high-level language with extensive - facilities for processing strings and structures. - The version of Icon for &os; can be found in the - Ports Collection as - lang/icon. + Icon 屬高階程式語言，Icon 具有強大的字串(String)和結構(Structure)處理能力。 + &os; Ports Collection 所收錄的 Icon 直譯器版本則是放在 + lang/icon。 Logo - Logo is a language that is easy to learn, and has - been used as an introductory programming language in - various courses. It is an excellent tool to work with - when teaching programming in small ages, as it makes the - creation of elaborate geometric shapes an easy task even - for very small children. - - The lastest version of Logo for &os; is available from - the Ports Collection in - lang/logo. + Logo 是種容易學習的程式語言，最常在一些教學課程中被拿來當作開頭範例。 + 如果要給小朋友開始上程式語言課的話，Logo 是相當不錯的選擇。 + 因為，即使對小朋友來說，要用 Logo 來秀出複雜多邊形圖形是相當輕鬆容易的。 + + Logo 在 &os; Ports Collection 的最新版則是放在 lang/logo。 Python - Python is an Object-Oriented, interpreted language. - Its advocates argue that it is one of the best languages - to start programming with, since it is relatively easy - to start with, but is not limited in comparison to other - popular interpreted languages that are used for the - development of large, complex applications (Perl and - Tcl are two other languages that are popular for such tasks). - - The latest version of Python is available from the - Ports Collection in - lang/python. + Python 是物件導向的直譯式語言， + Python 的擁護者總是宣稱 Python 是最好入門的程式語言。 + 雖然 Python 可以很簡單的開始，但是不代表它就會輸給其他直譯式語言(像是 Perl 和 Tcl)， + 事實證明 Python 也可以拿來開發大型、複雜的應用程式。 + + + &os; Ports Collection 收錄在 lang/python。 Ruby - Ruby is an interpreter, pure object-oriented programming - language. It has become widely popular because of its easy - to understand syntax, flexibility when writing code, and the - ability to easily develop and maintain large, complex - programs. - - Ruby is available from the Ports Collection as - lang/ruby18. + Ruby 是純物件導向的直譯式語言。 + Ruby 目前非常流行，原因在於他易懂的程式語法結構，在撰寫程式時的彈性， + 以及天生具有輕易的發展維護大型專案的能力。 + + &os; Ports Collection 收錄在 lang/ruby8。 Tcl and Tk - Tcl is an embeddable, interpreted language, that has - become widely used and became popular mostly because of its portability to many - platforms. It can be used both for quickly writing - small, prototype applications, or (when combined with - Tk, a GUI toolkit) fully-fledged, featureful - programs. - - Various versions of Tcl are available as ports - for &os;. The latest version, Tcl 8.4, can be found in - lang/tcl84. + Tcl 是內嵌式的直譯式語言，讓 Tcl 可以如此廣泛運用的原因是 Tcl 的移植性。 + Tcl 也可以快速發展一個簡單但是具有雛型的程式或者具有完整功能的程式。 + + Tcl 許多的版本都可在 &os; 上運作，而最新的 Tcl 版本為 Tcl 8.4， + &os; Ports Collection 收錄在 lang/tcl84。 - Compilers - - 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. + 編譯器 + 編譯器和直譯器兩者相比的話，有些不同，首先就是必須先把程式碼統統寫入到檔案裡面， + 然後必須執行編譯器來試著編譯程式，如果編譯器不接受所寫的程式，那就必須一直修改程式， + 直到編譯器接受且把你的程式編譯成執行檔。 + 此外，也可以在提示命令列，或在除錯器中執行你編譯好的程式看看它是否可以運作。 - If you run it in the shell, you may get a core - dump. + 如果在提示命令列下執行，那麼有可能會產生 core dump。 - 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 is also useful if you need to write very efficient - code, as the compiler can take its time and optimize the code, - which would not be acceptable in an interpreter. Moreover, - 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. - - 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. FreeBSD does not include Pascal - support in the base system, but both GNU Pascal Compiler (GPC) - and the Free Pascal Compiler - are available in the ports collection as - lang/gpc and - lang/fpc. - - As the edit-compile-run-debug cycle is rather tedious when - using separate programs, many commercial compiler makers have - produced Integrated Development Environments - (IDEs for short). FreeBSD does not include - an IDE in the base system, but devel/kdevelop is - available in the ports tree and many use - Emacs for this purpose. Using - Emacs as an IDE is discussed in - . + 很明顯的，使用編譯器並不像直譯器般可以馬上得到結果。 + 不管如何，編譯器允許你作很多直譯器不可能或者是很難達到的事情。 + 例如：撰寫和作業系統密切互動的程式，甚至是你自己寫的作業系統！ + 當你想要寫出高效率的程式時，編譯器便派上用場了。 + 編譯器可以在編譯時順便最佳化你的程式，但是直譯器卻不行。 + 而編譯器與直譯器最大的差別在於：當你想把你寫好的程式拿到另外一台機器上跑時， + 你只要將編譯器編譯出來的可執行檔，拿到新機器上便可以執行， + 而直譯器則必須要求新機器上，必須要有跟另一台機器上相同的直譯器， + 才能組譯執行你的程式！ + + + 編譯式的程式語言包含 Pascal、C 和 C++， + C 和 C++ 不是一個親和力十足的語言，但是很適合具有經驗的 Programmer。 + Pascal 其實是一個設計用來教學用的程式語言，而且也很適合用來入門， + &os; 預設並沒有把 Pascal 整合進 base system 中， + 但是 GNU Pascal Compiler 和 Free Pascal Compiler 都可分別在 + lang/gpc 和 lang/fpc 中找到。 + + 如果你用不同的程式來寫編譯式程式，那麼不斷地編輯-編譯-執行-除錯的這個循環肯定會很煩人， + 為了更簡化、方便程式開發流程，很多商業編譯器廠商開始發展所謂的 IDE(Integrated Development Environments) 開發環境， + FreeBSD 預設並沒有把 IDE 整合進 base system 中，但是你可透過 devel/kdevelop 安裝 kdevelop + 或使用 Emacs 來體驗 IDE 開發環境。 + 在後面的 專題將介紹，如何以 Emacs 來作為 IDE 開發環境。 - Compiling with <command>cc</command> + 用 <command>cc</command> 來編譯程式 - 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 cc or 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. + 本章範例只有針對 GNU C compiler 和 GNU C++ compiler 作說明， + 這兩個在 FreeBSD base system 中就有了， + 直接打 cc 或 gcc 就可以執行。 + 至於，如何用直譯器產生程式的說明，通常可在直譯器的文件或線上文件找到說明，因此不再贅述。 - Once you have 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. + 當你寫完你的傑作後，接下來便是讓這個程式可以在 FreeBSD 上執行， + 通常這些要一些步驟才能完成，有些步驟則需要不同程式來完成。 - Pre-process your source code to remove comments and do - other tricks like expanding macros in C. + 預先處理(Pre-process)你的程式碼，移除程式內的註解，和其他技巧， + 像是 expanding(擴大) C 的 marco。 - Check the syntax of your code to see if you have obeyed - the rules of the language. If you have not, it will - complain! + 確認你的程式語法是否確實遵照 C/C++ 的規定，如果沒有符合的話，編譯器會出現警告。 - Convert the source code into assembly - language—this is very close to machine code, but still - understandable by humans. Allegedly. - + 將原始碼轉成組合語言 — 它跟機器語言(machine code)非常相近，但仍在人類可理解的範圍內(據說應該是這樣)。 - To be strictly accurate, cc converts the - source code into its own, machine-independent - p-code instead of assembly language at - this stage. + 嚴格說起來，在這個階段 cc 並不是真的把原始程式轉成組合語言， + 而是轉為 machine-independent 的 p-code。 - Convert the assembly language into machine - code—yep, we are talking bits and bytes, ones and - zeros here. + 把組合語言轉成機器語言 — 是的，這裡說的機器語言就是常提到的 bit 和 byte，也就是 1 和 0。 - 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. + 確認程式中用到的函式呼叫、全域變數是否正確，舉例來說：如若呼叫了不存在的函式，編譯器會顯示警告。 - If you are trying to produce an executable from several - source code files, work out how to fit them all - together. + 如果程式是由程式碼檔案來編譯，編譯器會整合起來。 - Work out how to produce something that the system's - run-time loader will be able to load into memory and - run. + 編譯器會負責產生東西，讓系統上的 run-time loader 可以把程式載入記憶體內執行。 - Finally, write the executable on the filesystem. + 最後會把編譯完的執行檔存在硬碟上。 - The word compiling is often used to refer to - just steps 1 to 4—the others are referred to as - linking. Sometimes step 1 is referred to as - pre-processing and steps 3-4 as - assembling. - - Fortunately, almost all this detail is hidden from you, as - cc is a front end that manages calling all these - programs with the right arguments for you; simply typing + 通常 編譯(compiling) 是指第 1 到第 4 個步驟。 + — 其他步驟則稱為 連結(linking)， + 有時候步驟 1 也可以是指 預先處理(pre-processing)， + 而步驟 3 到步驟 4 則是 組譯(assembling)。 + 幸運的是，你可以不用理會以上細節，編譯器都會自動完成。 + 因為 cc 只是是個前端程式(front end)，它會依照正確的參數來呼叫相關程式幫你處理。 + 只需打： &prompt.user; cc foobar.c - will cause foobar.c to be compiled by all the - steps above. If you have more than one file to compile, just do - something like + 上述指令會把 foobar.c 開始編譯，並完成上述動作。 + 如果你有許多檔案需要編譯，那請打類似下列指令即可： &prompt.user; cc foo.c bar.c - 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. - + 記住語法錯誤檢查就是 — 純粹檢查語法錯誤與否， + 而不會幫你檢測任何邏輯錯誤，比如：無限迴圈，或是排序方式想用 binary sort 卻弄成 bubble sort。 - In case you did not know, a binary sort is an efficient - way of sorting things into order and a bubble sort - is not. + 剛所說的 binary sort 和 bubble sort 問題， + 在已排序好的序列中，binary sort 搜索效率會比 bubble sort 好。 - There are lots and lots of options for cc, which - are all in the manual page. Here are a few of the most important - ones, with examples of how to use them. + cc 有非常多的選項，都可透過線上手冊來查。 + 下面只提一些必要且重要的選項，以作為例子。 - + - The output name of the file. If you do not use this - option, cc will produce an executable called - a.out. + 編譯後的執行檔檔名，如果沒有使用這選項的話， + 編譯好的程式預設檔名將會是 a.out - The reasons for this are buried in the mists of - history. + 至於 的原因，則是一團歷史迷霧了。 - &prompt.user; cc foobar.c executable is a.out -&prompt.user; cc -o foobar foobar.c executable is foobar + &prompt.user; cc foobar.c 執行檔就是 a.out +&prompt.user; cc -o foobar foobar.c 執行檔就是 foobar - 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 Makefile. + 使用 時，只會編譯原始碼，而不作連結(linking)。 + 當只想確認語法是否正確或使用 Makefile 來編譯程式時，這個選項非常有用。 - &prompt.user; cc -c foobar.c + + &prompt.user; cc -c foobar.c - This will produce an object file (not an - executable) called foobar.o. This - can be linked together with other object files into an - executable. + 這會產生叫做 foobar 的 object file(非執行檔)。 + 這檔可以與其他的 object file 連結在一起，而成執行檔。 - 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 - very useful; the disadvantage is that - all this extra information makes the program much bigger. - Normally, you compile with while you - are developing a program and then compile a release - version without when you are - satisfied it works properly. + + 將會把一些給 gdb 用的除錯訊息包進去執行檔裡面，所謂的除錯訊息例如： + 程式在第幾行出錯、那個程式第幾行做什麼函式呼叫等等。除錯資訊非常好用。 + 但缺點就是：對於程式來說，額外的除錯訊息會讓編譯出來的程式比較肥些。 + 的適用時機在於：當程式還在開發時使用就好， + 而當你要釋出你的 發行版本(release version) + 或者確認程式可運作正常的話，就不必用 這選項了。 &prompt.user; cc -g foobar.c - This will produce a debug version of the - program. - + 這動作會產生有含除錯訊息的執行檔。 - Note, we did not use the flag - to specify the executable name, so we will get an - executable called a.out. - Producing a debug version called - foobar is left as an exercise for - the reader! + 請注意，因為上例沒用 以指定執行檔名稱， + 所以執行檔會是 a.out 這檔。 + 那麼，要如何產生 foobar 的執行檔並內含除錯訊息， + 這就留待看倌們練習一下囉。 - Create an optimized version of the executable. The - compiler performs various clever tricks to try to produce - an executable that runs faster than normal. You can add a - number after the to specify a higher - level of optimization, but this often exposes bugs in the - compiler's optimizer. For instance, the version of - cc that comes with the 2.1.0 release of - FreeBSD is known to produce bad code with the - option in some circumstances. - - Optimization is usually only turned on when compiling - a release version. + 會產生最佳化的執行檔， + 編譯器會使用一些技巧，來讓程式可以跑的比未經最佳化的程式還快， + 你可以在大寫 O 後面加上數字來指明你想要的最佳化層級。 + 但是最佳化還是會有一些錯誤，舉例來說在當在 FreeBSD 2.10 release 中使用 cc + 並且指定 時，在某些情形下會產生錯誤的執行檔。 + + 只有當要釋出發行版本、或者加速程式時，才需要使用最佳化選項。 + &prompt.user; cc -O -o foobar foobar.c - This will produce an optimized version of - foobar. + 這會產生 foobar 執行檔的最佳化版本。 - The following three flags will force cc - to check that your code complies to the relevant international - standard, often referred to as the ANSI - standard, though strictly speaking it is an - ISO standard. + + 以下三個參數將會強迫 cc 確認程式碼是否符合一些國際標準的規範， + 也就是通常說的 ANSI 標準， + 而 ANSI 嚴格來講屬 ISO 標準。 + - Enable all the warnings which the authors of - cc believe are worthwhile. Despite the - name, it will not enable all the warnings - cc is capable of. + 顯示 cc 維護者所認為值得注意的所有警告訊息。 + 不過這名字可能會造成誤解，事實上它並未完全顯示 cc 所能注意到的各項警告訊息。 - Turn off most, but not all, of the - non-ANSI C features provided by - cc. Despite the name, it does not - guarantee strictly that your code will comply to the - standard. + 關閉 cc 特有的某些特殊非 ANSI C 標準功能。 + 不過這名字可能會造成誤解，事實上它並不保證你的程式會完全符合 ANSI 標準。 - Turn off all - cc's non-ANSI C - features. + 全面關閉 cc 所特有的非 ANSI C 標準功能。 - Without these flags, cc 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 portable - code. + 除了這些參數，cc 還允許你使用一些額外的參數取代標準參數，有些額外參數非常有用， + 但是實際上並不是所有的編譯器都有提供這些參數。 + 照標準來寫程式的最主要目的就是，希望你寫出來的程式可以在所有編譯器上編譯、執行無誤， + 當程式可以達成上述目的時，就稱為 portable code(移植性良好的程式碼)。 - Generally, you should try to make your code as portable as - possible, as otherwise you may have to completely rewrite the - program later to get it to work somewhere else—and who - knows what you may be using in a few years time? + 一般來說，在撰寫程式時就應要注意『移植性』。 + 否則。當想把程式拿到另外一台機器上跑的時候，就可能得需要重寫程式。 &prompt.user; cc -Wall -ansi -pedantic -o foobar foobar.c - This will produce an executable foobar - after checking foobar.c for standard - compliance. + 上述指令會確認 foobar.c 內的語法是否符合標準， + 並且產生名為 foobar 的執行檔。 - Specify a function library to be used at link time. - - 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. - - The rule is that if the library is called - libsomething.a, - you give cc the argument - . - For example, the math library is - libm.a, so you give - cc the argument . - A common gotcha with the math library is - that it has to be the last library on the command - line. + 告訴 gcc 在連結(linking)程式時你需要用到的函式庫名稱。 + + 最常見的情況就是，當你在程式中使用了 C 數學函式庫， + 跟其他作業平台不一樣的是，這些數學函式都不在標準函式庫(library)中， + 因此編譯器並不知道這函式庫名稱，你必須告訴編譯器要加上它才行。 + + 這規則很簡單，如果有個函式庫叫做 libsomething/a， + 就必須在編譯時加上參數 才行。 + 舉例來說，數學函式庫叫做 libm.a， + 所以你必須給 cc 的參數就是 。 + 一般情況下，通常會把這參數必須放在指令的最後。 + &prompt.user; cc -o foobar foobar.c -lm - This will link the math library functions into - foobar. - - If you are compiling C++ code, you need to add - , or if - you are using FreeBSD 2.2 or later, to the command line - argument to link the C++ library functions. - Alternatively, you can run c++ instead - of cc, which does this for you. - c++ can also be invoked as - g++ on FreeBSD. + 上面這指令會讓 gcc 跟數學函式庫作連結，以便你的程式可以呼叫函式庫內含的數學函式。 + + 如果你正在編譯的程式是 C++ 程式碼，你還必須額外指定 或者是 + 。 + 如果你的 FreeBSD 是 2.2(含)以後版本， + 你可以用指令 c++ 來取代 cc。 + 在 FreeBSD 上 c++ 也可以用 g++ 取代。 + &prompt.user; cc -o foobar foobar.cc -lg++ For FreeBSD 2.1.6 and earlier &prompt.user; cc -o foobar foobar.cc -lstdc++ For FreeBSD 2.2 and later &prompt.user; c++ -o foobar foobar.cc Each of these will both produce an executable foobar from the C++ source file foobar.cc. Note that, on &unix; systems, C++ source files traditionally end in .C, .cxx or .cc, rather than the &ms-dos; style .cpp (which was already used for something else). gcc 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 .cpp with impunity! Common <command>cc</command> Queries and Problems I am trying to write a program which uses the sin() function and I get an error like this. What does it mean? /var/tmp/cc0143941.o: Undefined symbol `_sin' referenced from text segment When using mathematical functions like sin(), you have to tell cc to link in the math library, like so: &prompt.user; cc -o foobar foobar.c -lm All right, I wrote this simple program to practice using . All it does is raise 2.1 to the power of 6. #include <stdio.h> int main() { float f; f = pow(2.1, 6); printf("2.1 ^ 6 = %f\n", f); return 0; } and I compiled it as: &prompt.user; cc temp.c -lm like you said I should, but I get this when I run it: &prompt.user; ./a.out 2.1 ^ 6 = 1023.000000 This is not the right answer! What is going on? 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 int, which is definitely not what you want here. So how do I fix this? The prototypes for the mathematical functions are in math.h. If you include this file, the compiler will be able to find the prototype and it will stop doing strange things to your calculation! #include <math.h> #include <stdio.h> int main() { ... After recompiling it as you did before, run it: &prompt.user; ./a.out 2.1 ^ 6 = 85.766121 If you are using any of the mathematical functions, always include math.h and remember to link in the math library. I compiled a file called foobar.c and I cannot find an executable called foobar. Where has it gone? Remember, cc will call the executable a.out unless you tell it differently. Use the option: &prompt.user; cc -o foobar foobar.c OK, I have an executable called foobar, I can see it when I run ls, but when I type in foobar at the command prompt it tells me there is no such file. Why can it not find it? Unlike &ms-dos;, &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 ./foobar, which means run the file called foobar in the current directory, or change your PATH environment variable so that it looks something like bin:/usr/bin:/usr/local/bin:. The dot at the end means look in the current directory if it is not in any of the others. I called my executable test, but nothing happens when I run it. What is going on? Most &unix; systems have a program called test in /usr/bin and the shell is picking that one up before it gets to checking the current directory. Either type: &prompt.user; ./test or choose a better name for your program! I compiled my program and it seemed to run all right at first, then there was an error and it said something about core dumped. What does that mean? The name core dump 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 core, which the programmer could then pore over to find out what went wrong. Fascinating stuff, but what I am supposed to do now? Use gdb to analyze the core (see ). When my program dumped core, it said something about a segmentation fault. What is that? 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. Common causes for this are: Trying to write to a NULL pointer, eg char *foo = NULL; strcpy(foo, "bang!"); Using a pointer that has not been initialized, eg char *foo; strcpy(foo, "bang!"); The pointer will have some random value that, with luck, will point into an area of memory that is not available to your program and the kernel will kill your program before it can do any damage. If you are unlucky, it will point somewhere inside your own program and corrupt one of your data structures, causing the program to fail mysteriously. Trying to access past the end of an array, eg int bar[20]; bar[27] = 6; Trying to store something in read-only memory, eg char *foo = "My string"; strcpy(foo, "bang!"); &unix; compilers often put string literals like "My string" into read-only areas of memory. Doing naughty things with malloc() and free(), eg char bar[80]; free(bar); or char *foo = malloc(27); free(foo); free(foo); 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. Sometimes when I get a core dump it says bus error. It says in my &unix; book that this means a hardware problem, but the computer still seems to be working. Is this true? 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 should not have. 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 is an error? Yes, just go to another console or xterm, do &prompt.user; ps to find out the process ID of your program, and do &prompt.user; kill -ABRT pid where pid is the process ID you looked up. This is useful if your program has got stuck in an infinite loop, for instance. If your program happens to trap SIGABRT, there are several other signals which have a similar effect. Alternatively, you can create a core dump from inside your program, by calling the abort() function. See the manual page of &man.abort.3; to learn more. If you want to create a core dump from outside your program, but do not want the process to terminate, you can use the gcore program. See the manual page of &man.gcore.1; for more information. Make What is <command>make</command>? When you are working on a simple program with only one or two source files, typing in &prompt.user; cc file1.c file2.c is not too bad, but it quickly becomes very tedious when there are several files—and it can take a while to compile, too. 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: &prompt.user; cc file1.o file2.o … file37.c … if we had changed file37.c, but not any of the others, since the last time we compiled. This may speed up the compilation quite a bit, but does not solve the typing problem. 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. What happens if we have hundreds of source files lying about? What if we are working in a team with other people who forget to tell us when they have changed one of their source files that we use? 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 is a bit too complicated for the shell. This program is called make. It reads in a file, called a makefile, that tells it how different files depend on each other, and works out which files need to be re-compiled and which ones do not. For example, a rule could say something like if fromboz.o is older than fromboz.c, that means someone must have changed fromboz.c, so it needs to be re-compiled. The makefile also has rules telling make how to re-compile the source file, making it a much more powerful tool. Makefiles are typically kept in the same directory as the source they apply to, and can be called makefile, Makefile or MAKEFILE. Most programmers use the name Makefile, as this puts it near the top of a directory listing, where it can easily be seen. They do not use the MAKEFILE form as block capitals are often used for documentation files like README. Example of using <command>make</command> Here is a very simple make file: foo: foo.c cc -o foo foo.c It consists of two lines, a dependency line and a creation line. The dependency line here consists of the name of the program (known as the target), followed by a colon, then whitespace, then the name of the source file. When make reads this line, it looks to see if foo exists; if it exists, it compares the time foo was last modified to the time foo.c was last modified. If foo does not exist, or is older than foo.c, it then looks at the creation line to find out what to do. In other words, this is the rule for working out when foo.c needs to be re-compiled. The creation line starts with a tab (press the tab key) and then the command you would type to create foo if you were doing it at a command prompt. If foo is out of date, or does not exist, make then executes this command to create it. In other words, this is the rule which tells make how to re-compile foo.c. So, when you type make, it will make sure that foo is up to date with respect to your latest changes to foo.c. This principle can be extended to Makefiles with hundreds of targets—in fact, on FreeBSD, it is possible to compile the entire operating system just by typing make world in the appropriate directory! Another useful property of makefiles is that the targets do not have to be programs. For instance, we could have a make file that looks like this: foo: foo.c cc -o foo foo.c install: cp foo /home/me We can tell make which target we want to make by typing: &prompt.user; make target make will then only look at that target and ignore any others. For example, if we type make foo with the makefile above, make will ignore the install target. If we just type make on its own, make will always look at the first target and then stop without looking at any others. So if we typed make here, it will just go to the foo target, re-compile foo if necessary, and then stop without going on to the install target. Notice that the install target does not 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 make install. In this case, it will copy foo 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. This is a slightly confusing subject to try to explain. If you do not quite understand how make works, the best thing to do is to write a simple program like hello world 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 touch command is very useful here—it changes the date on a file without you having to edit it. Make and include-files C code often starts with a list of files to include, for example stdio.h. Some of these files are system-include files, some of them are from the project you are now working on: #include <stdio.h> #include "foo.h" int main(.... To make sure that this file is recompiled the moment foo.h is changed, you have to add it in your Makefile: foo: foo.c foo.h The moment your project is getting bigger and you have more and more own include-files to maintain, it will be a pain to keep track of all include files and the files which are depending on it. If you change an include-file but forget to recompile all the files which are depending on it, the results will be devastating. gcc has an option to analyze your files and to produce a list of include-files and their dependencies: . If you add this to your Makefile: depend: gcc -E -MM *.c > .depend and run make depend, the file .depend will appear with a list of object-files, C-files and the include-files: foo.o: foo.c foo.h If you change foo.h, next time you run make all files depending on foo.h will be recompiled. Do not forget to run make depend each time you add an include-file to one of your files. FreeBSD Makefiles 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 is the essential part of a typical ports Makefile: MASTER_SITES= ftp://freefall.cdrom.com/pub/FreeBSD/LOCAL_PORTS/ DISTFILES= scheme-microcode+dist-7.3-freebsd.tgz .include <bsd.port.mk> Now, if we go to the directory for this port and type make, the following happens: A check is made to see if the source code for this port is already on the system. If it is not, an FTP connection to the URL in MASTER_SITES is set up to download the source. 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. Any changes required to make the source work on FreeBSD are applied—this is known as patching. 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). The source code for the program is compiled. In effect, we change to the directory where the source was unpacked and do make—the program's own make file has the necessary information to build the program. 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 make install. 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 package database, so that the port can easily be uninstalled later if we change our mind about it. Now I think you will agree that is rather impressive for a four line script! The secret lies in the last line, which tells make to look in the system makefile called bsd.port.mk. It is easy to overlook this line, but this is where all the clever stuff comes from—someone has written a makefile that tells make to do all the things above (plus a couple of other things I did not 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! If you want to have a look at these system makefiles, they are in /usr/share/mk, but it is probably best to wait until you have 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!) More advanced uses of <command>make</command> Make is a very powerful tool, and can do much more than the simple example above shows. Unfortunately, there are several different versions of make, 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. The version of make that comes with FreeBSD is the Berkeley make; there is a tutorial for it in /usr/share/doc/psd/12.make. To view it, do &prompt.user; zmore paper.ascii.gz in that directory. Many applications in the ports use GNU make, which has a very good set of info pages. If you have installed any of these ports, GNU make will automatically have been installed as gmake. It is also available as a port and package in its own right. To view the info pages for GNU make, you will have to edit the dir file in the /usr/local/info directory to add an entry for it. This involves adding a line like * Make: (make). The GNU Make utility. to the file. Once you have done this, you can type info and then select make from the menu (or in Emacs, do C-h i). Debugging The Debugger The debugger that comes with FreeBSD is called gdb (GNU debugger). You start it up by typing &prompt.user; gdb progname although most people prefer to run it inside Emacs. You can do this by: M-x gdb RET progname RET 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 is already running, or load a core file to investigate why the program crashed. It is even possible to debug the kernel, though that is a little trickier than the user applications we will be discussing in this section. gdb 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. Finally, if you find its text-based command-prompt style off-putting, there is a graphical front-end for it (xxgdb) in the ports collection. This section is intended to be an introduction to using gdb and does not cover specialized topics such as debugging the kernel. Running a program in the debugger You will need to have compiled the program with the option to get the most out of using gdb. It will work without, but you will only see the name of the function you are in, instead of the source code. If you see a line like: … (no debugging symbols found) … when gdb starts up, you will know that the program was not compiled with the option. At the gdb prompt, type break main. 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 run 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 main(). (If you have ever wondered where main() gets called from, now you know!). You can now step through the program, a line at a time, by pressing n. If you get to a function call, you can step into it by pressing s. Once you are in a function call, you can return from stepping into a function call by pressing f. You can also use up and down to take a quick look at the caller. Here is a simple example of how to spot a mistake in a program with gdb. This is our program (with a deliberate mistake): #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; } This program sets i to be 5 and passes it to a function bazz() which prints out the number we gave it. When we compile and run the program we get &prompt.user; cc -g -o temp temp.c &prompt.user; ./temp This is my program anint = 4231 That was not what we expected! Time to see what is going on! &prompt.user; gdb temp 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) break main Skip the set-up code Breakpoint 1 at 0x160f: file temp.c, line 9. gdb puts breakpoint at main() (gdb) run Run as far as main() Starting program: /home/james/tmp/temp Program starts running Breakpoint 1, main () at temp.c:9 gdb stops at main() (gdb) n Go to next line This is my program Program prints out (gdb) s step into bazz() bazz (anint=4231) at temp.c:17 gdb displays stack frame (gdb) Hang on a minute! How did anint get to be 4231? Did we not we set it to be 5 in main()? Let's move up to main() and have a look. (gdb) up Move up call stack #1 0x1625 in main () at temp.c:11 gdb displays stack frame (gdb) p i Show us the value of i $1 = 4231 gdb displays 4231 Oh dear! Looking at the code, we forgot to initialize i. We meant to put … main() { int i; i = 5; printf("This is my program\n"); … but we left the i=5; line out. As we did not initialize i, it had whatever number happened to be in that area of memory when the program ran, which in this case happened to be 4231. gdb displays the stack frame every time we go into or out of a function, even if we are using up and down 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 is 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). Examining a core file A core file is basically a file which contains the complete state of the process when it crashed. In the good old days, 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 progname.core instead of just core, to make it clearer which program a core file belongs to. To examine a core file, start up gdb in the usual way. Instead of typing break or run, type (gdb) core progname.core If you are not in the same directory as the core file, you will have to do dir /path/to/core/file first. You should see something like this: &prompt.user; gdb a.out 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) core a.out.core 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) In this case, the program was called a.out, so the core file is called a.out.core. 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 bazz. Sometimes it is 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 bt command causes gdb to print out a back-trace of the call stack: (gdb) bt #0 0x164a in bazz (anint=0x5) at temp.c:17 #1 0xefbfd888 in end () #2 0x162c in main () at temp.c:11 (gdb) The end() function is called when a program crashes; in this case, the bazz() function was called from main(). Attaching to a running program One of the neatest features about gdb is that it can attach to a program that is 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. What you do is start up another gdb, use ps to find the process ID for the child, and do (gdb) attach pid in gdb, and then debug as usual. That is all very well, you are probably thinking, but by the time I have done that, the child process will be over the hill and far away. Fear not, gentle reader, here is how to do it (courtesy of the gdb info pages): … 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 */ … } else { /* parent */ … Now all you have to do is attach to the child, set PauseMode to 0, and wait for the sleep() call to return! Using Emacs as a Development Environment Emacs Unfortunately, &unix; systems do not come with the kind of everything-you-ever-wanted-and-lots-more-you-did-not-in-one-gigantic-package integrated development environments that other systems have. Some powerful, free IDEs now exist, such as KDevelop in the ports collection. 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 is free. And you have the source to it. The key to it all is Emacs. Now there are some people who loathe it, but many who love it. If you are one of the former, I am afraid this section will hold little of interest to you. Also, you will need a fair amount of memory to run it—I would recommend 8MB in text mode and 16MB in X as the bare minimum to get reasonable performance. Emacs is basically a highly customizable editor—indeed, it has been customized to the point where it is 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. It is impossible even to summarize everything Emacs can do here, but here are some of the features of interest to developers: Very powerful editor, allowing search-and-replace on both strings and regular expressions (patterns), jumping to start/end of block expression, etc, etc. Pull-down menus and online help. Language-dependent syntax highlighting and indentation. Completely customizable. You can compile and debug programs within Emacs. On a compilation error, you can jump to the offending line of source code. Friendly-ish front-end to the info program used for reading GNU hypertext documentation, including the documentation on Emacs itself. Friendly front-end to gdb, allowing you to look at the source code as you step through your program. You can read Usenet news and mail while your program is compiling. And doubtless many more that I have overlooked. Emacs can be installed on FreeBSD using the Emacs port. Once it is installed, start it up and do C-h t to read an Emacs tutorial—that means hold down the control key, press h, let go of the control key, and then press t. (Alternatively, you can you use the mouse to select Emacs Tutorial from the Help menu). Although Emacs does have menus, it is well worth learning the key bindings, as it is much quicker when you are editing something to press a couple of keys than to try to find the mouse and then click on the right place. And, when you are talking to seasoned Emacs users, you will find they often casually throw around expressions like M-x replace-s RET foo RET bar RET so it is 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. Fortunately, it is quite easy to pick up the key-bindings, as they are 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 are happy with that, move on to another menu command. If you can not remember what a particular combination of keys does, select Describe Key from the Help menu and type it in—Emacs will tell you what it does. You can also use the Command Apropos menu item to find out all the commands which contain a particular word in them, with the key binding next to it. By the way, the expression above means hold down the Meta key, press x, release the Meta key, type replace-s (short for replace-string—another feature of Emacs is that you can abbreviate commands), press the return key, type foo (the string you want replaced), press the return key, type bar (the string you want to replace foo with) and press return again. Emacs will then do the search-and-replace operation you have just requested. If you are wondering what on earth the Meta key is, it is a special key that many &unix; workstations have. Unfortunately, PC's do not have one, so it is usually the alt key (or if you are unlucky, the escape key). Oh, and to get out of Emacs, do C-x C-c (that means hold down the control key, press x, press c and release the control 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 C-z is the usual way to leave Emacs—that leaves Emacs hanging around in the background, and is only really useful if you are on a system which does not have virtual terminals). Configuring Emacs Emacs does many wonderful things; some of them are built in, some of them need to be configured. Instead of using a proprietary macro language for configuration, Emacs uses a version of Lisp specially adapted for editors, known as Emacs Lisp. Working with Emacs Lisp can be quite helpful if you want to go on and learn something like Common Lisp. Emacs Lisp has many features of Common Lisp, although it is considerably smaller (and thus easier to master). The best way to learn Emacs Lisp is to download the Emacs Tutorial However, there is no need to actually know any Lisp to get started with configuring Emacs, as I have included a sample .emacs file, which should be enough to get you started. Just copy it into your home directory and restart Emacs if it is already running; it will read the commands from the file and (hopefully) give you a useful basic setup. A sample <filename>.emacs</filename> file Unfortunately, there is far too much here to explain it in detail; however there are one or two points worth mentioning. Everything beginning with a ; is a comment and is ignored by Emacs. In the first line, the -*- Emacs-Lisp -*- is so that we can edit the .emacs 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 .emacs. The tab 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 tab character in whatever you are writing, hold the control key down while you are pressing the tab key. This file supports syntax highlighting for C, C++, Perl, Lisp and Scheme, by guessing the language from the filename. Emacs already has a pre-defined function called next-error. In a compilation output window, this allows you to move from one compilation error to the next by doing M-n; we define a complementary function, previous-error, that allows you to go to a previous error by doing M-p. The nicest feature of all is that C-c C-c will open up the source file in which the error occurred and jump to the appropriate line. We enable Emacs's ability to act as a server, so that if you are doing something outside Emacs and you want to edit a file, you can just type in &prompt.user; emacsclient filename and then you can edit the file in your Emacs! Many Emacs users set their EDITOR environment to emacsclient so this happens every time they need to edit a file. A sample <filename>.emacs</filename> file ;; -*-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") (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))) ;; 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) (if (>= emacs-major-version 21) (setq show-trailing-whitespace t)) ;; 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 color &optional bold) "Create a face from a color and optionally make it bold" (make-face face) (copy-face 'default face) (set-face-foreground face color) (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) ".") Extending the Range of Languages Emacs Understands Now, this is all very well if you only want to program in the languages already catered for in the .emacs file (C, C++, Perl, Lisp and Scheme), but what happens if a new language called whizbang comes out, full of exciting features? The first thing to do is find out if whizbang comes with any files that tell Emacs about the language. These usually end in .el, short for Emacs Lisp. For example, if whizbang is a FreeBSD port, we can locate these files by doing &prompt.user; find /usr/ports/lang/whizbang -name "*.el" -print and install them by copying them into the Emacs site Lisp directory. On FreeBSD 2.1.0-RELEASE, this is /usr/local/share/emacs/site-lisp. So for example, if the output from the find command was /usr/ports/lang/whizbang/work/misc/whizbang.el we would do &prompt.root; cp /usr/ports/lang/whizbang/work/misc/whizbang.el /usr/local/share/emacs/site-lisp Next, we need to decide what extension whizbang source files have. Let's say for the sake of argument that they all end in .wiz. We need to add an entry to our .emacs file to make sure Emacs will be able to use the information in whizbang.el. Find the auto-mode-alist entry in .emacs and add a line for whizbang, such as: … ("\\.lsp$" . lisp-mode) ("\\.wiz$" . whizbang-mode) ("\\.scm$" . scheme-mode) … This means that Emacs will automatically go into whizbang-mode when you edit a file ending in .wiz. Just below this, you will find the font-lock-auto-mode-list entry. Add whizbang-mode to it like so: ;; 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") This means that Emacs will always enable font-lock-mode (ie syntax highlighting) when editing a .wiz file. And that is all that is needed. If there is anything else you want done automatically when you open up a .wiz file, you can add a whizbang-mode hook (see my-scheme-mode-hook for a simple example that adds auto-indent). Further Reading For information about setting up a development environment for contributing fixes to FreeBSD itself, please see &man.development.7;. Brian Harvey and Matthew Wright Simply Scheme MIT 1994. ISBN 0-262-08226-8 Randall Schwartz Learning Perl O'Reilly 1993 ISBN 1-56592-042-2 Patrick Henry Winston and Berthold Klaus Paul Horn Lisp (3rd Edition) Addison-Wesley 1989 ISBN 0-201-08319-1 Brian W. Kernighan and Rob Pike The Unix Programming Environment Prentice-Hall 1984 ISBN 0-13-937681-X Brian W. Kernighan and Dennis M. Ritchie The C Programming Language (2nd Edition) Prentice-Hall 1988 ISBN 0-13-110362-8 Bjarne Stroustrup The C++ Programming Language Addison-Wesley 1991 ISBN 0-201-53992-6 W. Richard Stevens Advanced Programming in the Unix Environment Addison-Wesley 1992 ISBN 0-201-56317-7 W. Richard Stevens Unix Network Programming Prentice-Hall 1990 ISBN 0-13-949876-1