Unix programe tools

Unix
Programming
Tools
By Parlante, Zelenski, and many others Copyright ©1998-2001, Stanford University
Introduction
This article explains the overall edit-compile-link-debug programming cycle and
introduces several common Unix programming tools -- gcc, make, gdb, emacs, and the
Unix shell. The goal is to describe the major features and typcial uses of the tools and
show how they fit together with enough detail for simple projects. We've used a version
of this article at Stanford to help students get started with Unix.
Contents
Introduction — the compile-link process 1
The gcc compiler/linker 2
The make project utility 5
The gdb debugger 8
The emacs editor 13
Summary of Unix shell commands 15
This is document #107, Unix Programming Tools, in the Stanford CS Education Library.
This and other free educational materials are available at http://cslibrary.stanford.edu/.
This document is free to be used, reproduced, or sold so long as it is intact and
unchanged.
Other Resources
This article is an introduction — for more detailed information about a particular tool, see
the tool's man pages and xinfo entries. Also, O'Reilly & Associates publishes a pretty
good set of references for many Unix related tools (the books with animal pictures on the
cover). For basic coverage of the C programming language, see CS Education Library
#101, (http://cslibrary.stanford.edu/101/).
The Compile Process
Before going into detail about the individual tools themselves, it is useful to review the
overall process that goes into building an executable program. After the source text files
have been edited, there are two steps in the build process: compiling and linking. Each
source file (foo.c) is compiled into an object file (foo.o). Each object file contain a system
dependent, compiled representation of the program as described in its source file.
Typically the file name of an object module is the same as the source file that produced it,
but with a ".o" file extension — "main.c" is compiled to produce "main.o". The .o file
will include references, known as symbols, to functions, variables, etc. that the code
needs. The individual object files are then linked together to produce a single executable
file which the system loader can use when the program is actually run. The link step will
2
also bring in library object files that contain the definitions of library functions like
printf() and malloc(). The overall process looks like this...
main.c module1.c module2.c
main.o module1.o module2.o
program
library
functions
C compiler
Linker
Section 1 — gcc
The following discussion is about the gcc compiler, a product of the open-source GNU
project (www.gnu.org). Using gcc has several advantages— it tends to be pretty up-todate
and reliable, it's available on a variety of platforms, and of course it's free and opensource.
Gcc can compile C, C , and objective-C. Gcc is actually both a compiler and a
linker. For simple problems, a single call to gcc will perform the entire compile-link
operation. For example, for small projects you might use a command like the following
which compiles and links together three .c files to create an executable named "program".
gcc main.c module1.c module2.c -o program
The above line equivalently could be re-written to separate out the three compilation

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