DOCSLIB.ORG

1 More Unix Commands Unix User Settings Makefile Core Dump GDB More C Preprocessor Extern Keyword in C

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
1 More Unix Commands Unix User Settings Makefile Core Dump GDB More C Preprocessor Extern Keyword in C Redirection • Command > file More Unix Commands Redirects command output to a file Unix User Settings If file already created, then overwrites the file Makefile ¾ >> use to append Core Dump E.g. ls > dump.txt GDB More C Preprocessor • Command < file Extern keyword in C Command is run and its input is taken from file (instead of stdin) See example: redirection.c CIT 593 a.out < inputfile > outputfile CIT593 2 grep Shell Variables • Search text within a file • Predefined Variables examples HOME ¾ Contains user home directory path • grep searchterm filename/directorypath PATH ¾ Contains all the search paths for your shell Can use regular expression terms such (*), (.), (\) SHELL • E.g. grep world* filename ¾ Tells which is your default shell • In order use these variables you need to put $ sign in Prints lines containing all words starting with world front of the variable name. E.g. in file echo $HOME -> prints your home directory path (even if you • E. g. grep world** are not in yyy)our home directory) ¾ echo is shell command to print Prints lines containing all words starting with world ¾ If you do not put the $ sign then it will just print “HOME” in files within the directory – \ before $HOME will just print home (so \ removes special meaning from a single character) CIT593 3 CIT593 4 1 .cshrc or .bashsrc file Customizing .cshrc Example • Are files for customizing shells # if you want to add directories to your search path, add them before # the "." in the line below. For example, .cshsrc for csh or tcsh shell # # set path = ( $path ~ ~/bin ~/scripts . ) .bashrc for bash shell set path = ($path /usr/java/jdk1.5.0/bin .) • These files contains commands, variable # to be automatically logged out after 30min of inactivity: definitions and aliases used any time the type # set autologout=(30) shell is run. unset autologout When one logs in, for e. g. C shell starts by reading #####DIANA######## the .cshrc file, and sets up any variables and if ($?prompt) set prompt = "palsetia%c04:“ aliases alias c clear alias p pine CIT593 5 CIT593 6 After editing .cshrc/.bashrc Core Dump • At the prompt type: source .cshrc • A core dump is the name often given to the recorded state of the working memory of a computer program This will allow the changes to take place effectively at a specific time generally when the program that has terminated abnormally Otherwise, the changes will take place next time you login ¾ Because .cshrc script is executed once i.e. • Is a simply a binary file with the sequence of bytes or executed when user logs in words containing the memory image of a particular process. • Name of file is “core” without any extensions and the file appears in the current working directory CIT593 7 CIT593 8 2 Core Dump (contd..) Core Dump (contd..) Abnormal Program Termination Issue with core file Often buffer overflows, where a programmer allocates too Core file is often very large and takes up a lot of disk space little memory for incoming or computed data One can avoid exceeding the disk quota with a large core file Access to null pointers, a common coding error when an by limiting the core dump size unassigned memory reference variable is accessed Uses of core dump csh/tcsh shell A runtime error such as “Segmentation Fault” does not limit coredumpsize 0 describe as to where does the problem lie limit coredumpsize 10240 # Limit core dumps to Core dump can help reveal where the fault is occurring 10 megs ¾ Programmer can try to interpret the file but needs enough knowledge of structure of the programs memory use unlimit coredumpsize # Allow unlimited-sized ¾ Special Programs such as GDB debugger or dump coredumps analyzers can relieve the programmer from reading core file which is in hex bytes CIT593 9 CIT593 10 make Example: makefile (with targets) make is a compilation tool #is a comment COMPILER=gcc make compiles, assembles, and links your source LIBS=-lm #needed to compile Math.h files OPTIONS=-Wall Think of it as the lcs file in PennSim simulator NAME1= hypo tenuse command The file you write is called “makefile” without any NAME2=main file extensions NAME3= hypo ¾ makefile is read by program make all: Then at prompt type : make targetname $(COMPILER) $(LIBS) $(OPTIONS) $(NAME1).c $(NAME2).c -o $(NAME3) # To remove executable or .o files generated # Type: make clean clean: rm -f $(NAME3) CIT593 11 CIT593 12 3 makefile: Rule Syntax makefile: Rule Syntax (contd..) A rule tells make two things: • The targets are named sections (like a LABEL) to tell make what to execute when the targets are out of date There can be more than one target how to update them when necessary. When use make, specify the target you want ¾ If targetname is not provided, then the make executes In general, a rule looks like this: the first target in the file targets : prerequisites The command lines start with a tab character (‘\t’) The first command may appear on the line after the <‘\t’>command prerequisites, with a tab character, or may appear on the same line, with a semicolon You may split a long line by inserting a backslash followed ... or like this: by a newline ¾ But this is not required, as make places no limit on the targets : prerequisites ; command command ... length of a line in a makefile CIT593 13 CIT593 14 Makefile (prerequites and commands) GDB Debugger #is a comment GDB stands for GNU Debugger COMPILER=gcc LIBS=-lm #needed to compile Math.h GDB is a Unix terminal debugger, which can OPTIONS=-Wall prerequisites execute your program in a sandbox and allow you NAME1=hypotenuse to analyze it during runtime NAME2=main NAME3= hypo Most helpful to catch segmentation fault error ¾ all: hypotenuse.c main.c hypotenuse.h Can pin-point exactly where in your code it $(COMPILER) $(LIBS) $(OPTIONS) $(NAME1).c $(NAME2).c -o $(NAME3) happening # To remove executable or .o files generated Follow the GDB tutorial on how to use GDB tool # Type: make clean clean: If any of the prerequisites are rm -f $(NAME3) missing make will not execute the target command CIT593 15 CIT593 16 4 More Preprocessor: #ifdef Example #ifdef MACRO #define DEBUG //#define DEBUG controlled text int main() { int main() { #endif int x; int x; .. .. #ifdef DEBUG #ifdef DEBUG The block is called conditional group printf(“The value of x printf(“The value of x The controlled text will be included in the %d\n”, x); %d\n”, x); output of the preprocessor if and only if #endif #endif MACRO is defined …. …. } Conditional succeeds if MACRO is designed. Print statement is Print statement is not executed as DEBUG } executed as DEBUG is defined is not defined CIT593 17 CIT593 18 More Preprocessor: #ifndef Example #ifndef MACRO #ifndef EXTENDED controlled text #define MAX_LEN 50 #endif #else #define MAX_LEN 75 Checks whether a macro is define or not #endif If macro is not define then the lines of code immediately following the condition are If EXTENDED is not defined then MAX_ LEN is passed on the compiler defined to be 50 else is defined to be 75 CIT593 19 CIT593 20 5 Another Example with ifndef Extern in C Note that scope of global variable is limited to the file it is declared in. //In packets_main.c #include “packets.h” The keyword “extern” in C indicates the existence of global variable or function that is defined in another file #ifndef TEST _ MAIN Ifil1In file1.c int main(){ int x = 1; //global (declared outside of all functions) … In file2.c } extern int x; //tells the compiler to look for definition of x elsewhere #endif int main(){ Allows for testing with different main than the users main printf(“%d\n”,x); x++; E. g. packets. h will define the macro TEST_ MAIN printf(“%d\n”,x); Allows other implemented functions in packets_main.c to be still } accessed by another program with giving compiler errors of multiple definitions of mains. If you forget to put extern it will still work as the linker will resolve the reference across multiple files, however the intent then is unclear and can lead to error prone in case of typos. CIT593 21 CIT593 22 6.
Load more

Recommended publications
  • Introduction to Debugging the Freebsd Kernel
    Introduction to Debugging the FreeBSD Kernel John H. Baldwin Yahoo!, Inc. Atlanta, GA 30327 [email protected], http://people.FreeBSD.org/˜jhb Abstract used either directly by the user or indirectly via other tools such as kgdb [3]. Just like every other piece of software, the The Kernel Debugging chapter of the FreeBSD kernel has bugs. Debugging a ker- FreeBSD Developer’s Handbook [4] covers nel is a bit different from debugging a user- several details already such as entering DDB, land program as there is nothing underneath configuring a system to save kernel crash the kernel to provide debugging facilities such dumps, and invoking kgdb on a crash dump. as ptrace() or procfs. This paper will give a This paper will not cover these topics. In- brief overview of some of the tools available stead, it will demonstrate some ways to use for investigating bugs in the FreeBSD kernel. FreeBSD’s kernel debugging tools to investi- It will cover the in-kernel debugger DDB and gate bugs. the external debugger kgdb which is used to perform post-mortem analysis on kernel crash dumps. 2 Kernel Crash Messages 1 Introduction The first debugging service the FreeBSD kernel provides is the messages the kernel prints on the console when the kernel crashes. When a userland application encounters a When the kernel encounters an invalid condi- bug the operating system provides services for tion (such as an assertion failure or a memory investigating the bug. For example, a kernel protection violation) it halts execution of the may save a copy of the a process’ memory current thread and enters a “panic” state also image on disk as a core dump.
    [Show full text]
  • Process and Memory Management Commands
    Process and Memory Management Commands This chapter describes the Cisco IOS XR software commands used to manage processes and memory. For more information about using the process and memory management commands to perform troubleshooting tasks, see Cisco ASR 9000 Series Aggregation Services Router Getting Started Guide. • clear context, on page 2 • dumpcore, on page 3 • exception coresize, on page 6 • exception filepath, on page 8 • exception pakmem, on page 12 • exception sparse, on page 14 • exception sprsize, on page 16 • follow, on page 18 • monitor threads, on page 25 • process, on page 29 • process core, on page 32 • process mandatory, on page 34 • show context, on page 36 • show dll, on page 39 • show exception, on page 42 • show memory, on page 44 • show memory compare, on page 47 • show memory heap, on page 50 • show processes, on page 54 Process and Memory Management Commands 1 Process and Memory Management Commands clear context clear context To clear core dump context information, use the clear context command in the appropriate mode. clear context location {node-id | all} Syntax Description location{node-id | all} (Optional) Clears core dump context information for a specified node. The node-id argument is expressed in the rack/slot/module notation. Use the all keyword to indicate all nodes. Command Default No default behavior or values Command Modes Administration EXEC EXEC mode Command History Release Modification Release 3.7.2 This command was introduced. Release 3.9.0 No modification. Usage Guidelines To use this command, you must be in a user group associated with a task group that includes appropriate task IDs.
    [Show full text]
  • Red Hat Enterprise Linux 6 Developer Guide
    Red Hat Enterprise Linux 6 Developer Guide An introduction to application development tools in Red Hat Enterprise Linux 6 Dave Brolley William Cohen Roland Grunberg Aldy Hernandez Karsten Hopp Jakub Jelinek Developer Guide Jeff Johnston Benjamin Kosnik Aleksander Kurtakov Chris Moller Phil Muldoon Andrew Overholt Charley Wang Kent Sebastian Red Hat Enterprise Linux 6 Developer Guide An introduction to application development tools in Red Hat Enterprise Linux 6 Edition 0 Author Dave Brolley [email protected] Author William Cohen [email protected] Author Roland Grunberg [email protected] Author Aldy Hernandez [email protected] Author Karsten Hopp [email protected] Author Jakub Jelinek [email protected] Author Jeff Johnston [email protected] Author Benjamin Kosnik [email protected] Author Aleksander Kurtakov [email protected] Author Chris Moller [email protected] Author Phil Muldoon [email protected] Author Andrew Overholt [email protected] Author Charley Wang [email protected] Author Kent Sebastian [email protected] Editor Don Domingo [email protected] Editor Jacquelynn East [email protected] Copyright © 2010 Red Hat, Inc. and others. The text of and illustrations in this document are licensed by Red Hat under a Creative Commons Attribution–Share Alike 3.0 Unported license ("CC-BY-SA"). An explanation of CC-BY-SA is available at http://creativecommons.org/licenses/by-sa/3.0/. In accordance with CC-BY-SA, if you distribute this document or an adaptation of it, you must provide the URL for the original version. Red Hat, as the licensor of this document, waives the right to enforce, and agrees not to assert, Section 4d of CC-BY-SA to the fullest extent permitted by applicable law.
    [Show full text]
  • Winappdbg Documentation Release 1.6
    WinAppDbg Documentation Release 1.6 Mario Vilas Aug 28, 2019 Contents 1 Introduction 1 2 Programming Guide 3 i ii CHAPTER 1 Introduction The WinAppDbg python module allows developers to quickly code instrumentation scripts in Python under a Win- dows environment. It uses ctypes to wrap many Win32 API calls related to debugging, and provides a powerful abstraction layer to manipulate threads, libraries and processes, attach your script as a debugger, trace execution, hook API calls, handle events in your debugee and set breakpoints of different kinds (code, hardware and memory). Additionally it has no native code at all, making it easier to maintain or modify than other debuggers on Windows. The intended audience are QA engineers and software security auditors wishing to test or fuzz Windows applications with quickly coded Python scripts. Several ready to use tools are shipped and can be used for this purposes. Current features also include disassembling x86/x64 native code, debugging multiple processes simultaneously and produce a detailed log of application crashes, useful for fuzzing and automated testing. Here is a list of software projects that use WinAppDbg in alphabetical order: • Heappie! is a heap analysis tool geared towards exploit writing. It allows you to visualize the heap layout during the heap spray or heap massaging stage in your exploits. The original version uses vtrace but here’s a patch to use WinAppDbg instead. The patch also adds 64 bit support. • PyPeElf is an open source GUI executable file analyzer for Windows and Linux released under the BSD license. • python-haystack is a heap analysis framework, focused on classic C structure matching.
    [Show full text]
  • Post Mortem Crash Analysis
    Post Mortem Crash Analysis Johan Heander & Magnus Malmborn January 14, 2007 Abstract To improve the quality and reliability of embedded systems it is important to gather information about errors in units already sold and deployed. To achieve this, a system for transmitting error information from the customer back to the developers is needed, and the developers must also have a set of tools to analyze the error reports. The purpose of this master thesis was to develop a fully functioning demon- stration system for collection, transmission and interpretation of error reports from Axis network cameras using the Linux operating system. The system has been shown to handle both kernel and application errors and conducts automatic analysis of received data. It also uses standard HTTP protocol for all network transfers making it easy to use even on firewalled net- works. i ii Acknowledgement We would like to thank our LTH supervisor Jonas Skeppstedt for all he has taught us about computer science in general and operating systems and the C programming language in particular. We would also like to thank Mikael Starvik at Axis Communications for quickly providing us with all hardware and information we needed to complete this thesis, and for providing us with support during our implementation and writing. Finally we thank all the developers working at Axis Communications, many of whom have provided input and reflections on our work. iii iv Contents 1 Introduction 1 1.1 Problem description . 1 1.2 Problem analysis . 1 2 Background 3 2.1 Kernel crashes . 3 2.2 User space crashes .
    [Show full text]
  • Using the GNU Debugger (Gdb) a Debugger Is a Very Useful Tool for Finding Bugs in a Program
    Using the GNU debugger (gdb) A debugger is a very useful tool for finding bugs in a program. You can interact with a program while it is running, start and stop it whenever, inspect the current values of variables and modify them, etc. If your program runs and crashes, it will produce a ‘core dump’. You can also use a debugger to look at the core dump and give you extra information about where the crash happened and what triggered it. Some debuggers (including recent versions of gdb) can also go backwards through your code: you run your code forwards in time to the point of an error, and then go backwards looking at the values of the key variables until you get to the start of the error. This can be slow but useful sometimes! To use a debugger effectively, you need to get the compiler to put extra ‘symbol’ information into the binary, otherwise all it will contain is machine code level – it is much more useful to have the actual variable names you used. To do this, you use: gfortran –g –O0 mycode.f90 –o mybinary where ‘-g’ is the compiler option to include extra symbols, -O0 is no optimization so the code is compiled exactly as written, and the output binary is called ’mybinary’. If the source files and executable file is in the same directory, then you can run the binary through the debugger by simply doing: gdb ./mybinary This will then put you into an interactive debugging session. Most commands can be shortened (eg ‘b’ instead of ‘break’) and pressing ‘enter’ will repeat the last command.
    [Show full text]
  • Bringing GNU Emacs to Native Code
    Bringing GNU Emacs to Native Code Andrea Corallo Luca Nassi Nicola Manca [email protected] [email protected] [email protected] CNR-SPIN Genoa, Italy ABSTRACT such a long-standing project. Although this makes it didactic, some Emacs Lisp (Elisp) is the Lisp dialect used by the Emacs text editor limitations prevent the current implementation of Emacs Lisp to family. GNU Emacs can currently execute Elisp code either inter- be appealing for broader use. In this context, performance issues preted or byte-interpreted after it has been compiled to byte-code. represent the main bottleneck, which can be broken down in three In this work we discuss the implementation of an optimizing com- main sub-problems: piler approach for Elisp targeting native code. The native compiler • lack of true multi-threading support, employs the byte-compiler’s internal representation as input and • garbage collection speed, exploits libgccjit to achieve code generation using the GNU Com- • code execution speed. piler Collection (GCC) infrastructure. Generated executables are From now on we will focus on the last of these issues, which con- stored as binary files and can be loaded and unloaded dynamically. stitutes the topic of this work. Most of the functionality of the compiler is written in Elisp itself, The current implementation traditionally approaches the prob- including several optimization passes, paired with a C back-end lem of code execution speed in two ways: to interface with the GNU Emacs core and libgccjit. Though still a work in progress, our implementation is able to bootstrap a func- • Implementing a large number of performance-sensitive prim- tional Emacs and compile all lexically scoped Elisp files, including itive functions (also known as subr) in C.
    [Show full text]
  • A.5.1. Linux Programming and the GNU Toolchain
    Making the Transition to Linux A Guide to the Linux Command Line Interface for Students Joshua Glatt Making the Transition to Linux: A Guide to the Linux Command Line Interface for Students Joshua Glatt Copyright © 2008 Joshua Glatt Revision History Revision 1.31 14 Sept 2008 jg Various small but useful changes, preparing to revise section on vi Revision 1.30 10 Sept 2008 jg Revised further reading and suggestions, other revisions Revision 1.20 27 Aug 2008 jg Revised first chapter, other revisions Revision 1.10 20 Aug 2008 jg First major revision Revision 1.00 11 Aug 2008 jg First official release (w00t) Revision 0.95 06 Aug 2008 jg Second beta release Revision 0.90 01 Aug 2008 jg First beta release License This document is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License [http:// creativecommons.org/licenses/by-nc-sa/3.0/us/]. Legal Notice This document is distributed in the hope that it will be useful, but it is provided “as is” without express or implied warranty of any kind; without even the implied warranties of merchantability or fitness for a particular purpose. Although the author makes every effort to make this document as complete and as accurate as possible, the author assumes no responsibility for errors or omissions, nor does the author assume any liability whatsoever for incidental or consequential damages in connection with or arising out of the use of the information contained in this document. The author provides links to external websites for informational purposes only and is not responsible for the content of those websites.
    [Show full text]
  • The Glib/GTK+ Development Platform
    The GLib/GTK+ Development Platform A Getting Started Guide Version 0.8 Sébastien Wilmet March 29, 2019 Contents 1 Introduction 3 1.1 License . 3 1.2 Financial Support . 3 1.3 Todo List for this Book and a Quick 2019 Update . 4 1.4 What is GLib and GTK+? . 4 1.5 The GNOME Desktop . 5 1.6 Prerequisites . 6 1.7 Why and When Using the C Language? . 7 1.7.1 Separate the Backend from the Frontend . 7 1.7.2 Other Aspects to Keep in Mind . 8 1.8 Learning Path . 9 1.9 The Development Environment . 10 1.10 Acknowledgments . 10 I GLib, the Core Library 11 2 GLib, the Core Library 12 2.1 Basics . 13 2.1.1 Type Definitions . 13 2.1.2 Frequently Used Macros . 13 2.1.3 Debugging Macros . 14 2.1.4 Memory . 16 2.1.5 String Handling . 18 2.2 Data Structures . 20 2.2.1 Lists . 20 2.2.2 Trees . 24 2.2.3 Hash Tables . 29 2.3 The Main Event Loop . 31 2.4 Other Features . 33 II Object-Oriented Programming in C 35 3 Semi-Object-Oriented Programming in C 37 3.1 Header Example . 37 3.1.1 Project Namespace . 37 3.1.2 Class Namespace . 39 3.1.3 Lowercase, Uppercase or CamelCase? . 39 3.1.4 Include Guard . 39 3.1.5 C++ Support . 39 1 3.1.6 #include . 39 3.1.7 Type Definition . 40 3.1.8 Object Constructor . 40 3.1.9 Object Destructor .
    [Show full text]
  • Linux Core Dumps
    Linux Core Dumps Kevin Grigorenko [email protected] Many Interactions with Core Dumps systemd-coredump abrtd Process Crashes Ack! 4GB File! Most Interactions with Core Dumps Poof! Process Crashes systemd-coredump Nobody abrtd Looks core kdump not Poof! Kernel configured Crashes So what? ● Crashes are problems! – May be symptoms of security vulnerabilities – May be application bugs ● Data corruption ● Memory leaks – A hard crash kills outstanding work – Without automatic process restarts, crashes lead to service unavailability ● With restarts, a hacker may continue trying. ● We shouldn't be scared of core dumps. – When a dog poops inside the house, we don't just `rm -f $poo` or let it pile up, we try to figure out why or how to avoid it again. What is a core dump? ● It's just a file that contains virtual memory contents, register values, and other meta-data. – User land core dump: Represents state of a particular process (e.g. from crash) – Kernel core dump: Represents state of the kernel (e.g. from panic) and process data ● ELF-formatted file (like a program) User Land User Land Crash core Process 1 Process N Kernel Panic vmcore What is Virtual Memory? ● Virtual Memory is an abstraction over physical memory (RAM/swap) – Simplifies programming – User land: process isolation – Kernel/processor translate virtual address references to physical memory locations 64-bit Process Virtual 8GB RAM Address Space (16EB) (Example) 0 0 16 8 EB GB How much virtual memory is used? ● Use `ps` or similar tools to query user process virtual memory usage (in KB): – $ ps -o pid,vsz,rss -p 14062 PID VSZ RSS 14062 44648 42508 Process 1 Virtual 8GB RAM Memory Usage (VSZ) (Example) 0 0 Resident Page 1 Resident Page 2 16 8 EB GB Process 2 How much virtual memory is used? ● Virtual memory is broken up into virtual memory areas (VMAs), the sum of which equal VSZ and may be printed with: – $ cat /proc/${PID}/smaps 00400000-0040b000 r-xp 00000000 fd:02 22151273 /bin/cat Size: 44 kB Rss: 20 kB Pss: 12 kB..
    [Show full text]
  • The Complete Freebsd
    The Complete FreeBSD® If you find errors in this book, please report them to Greg Lehey <grog@Free- BSD.org> for inclusion in the errata list. The Complete FreeBSD® Fourth Edition Tenth anniversary version, 24 February 2006 Greg Lehey The Complete FreeBSD® by Greg Lehey <[email protected]> Copyright © 1996, 1997, 1999, 2002, 2003, 2006 by Greg Lehey. This book is licensed under the Creative Commons “Attribution-NonCommercial-ShareAlike 2.5” license. The full text is located at http://creativecommons.org/licenses/by-nc-sa/2.5/legalcode. You are free: • to copy, distribute, display, and perform the work • to make derivative works under the following conditions: • Attribution. You must attribute the work in the manner specified by the author or licensor. • Noncommercial. You may not use this work for commercial purposes. This clause is modified from the original by the provision: You may use this book for commercial purposes if you pay me the sum of USD 20 per copy printed (whether sold or not). You must also agree to allow inspection of printing records and other material necessary to confirm the royalty sums. The purpose of this clause is to make it attractive to negotiate sensible royalties before printing. • Share Alike. If you alter, transform, or build upon this work, you may distribute the resulting work only under a license identical to this one. • For any reuse or distribution, you must make clear to others the license terms of this work. • Any of these conditions can be waived if you get permission from the copyright holder. Your fair use and other rights are in no way affected by the above.
    [Show full text]
  • GDB Tutorial a Walkthrough with Examples
    GDB Tutorial A Walkthrough with Examples CMSC 212 - Spring 2009 Last modified March 22, 2009 GDB Tutorial What is gdb? “GNU Debugger” A debugger for several languages, including C and C++ It allows you to inspect what the program is doing at a certain point during execution. Errors like segmentation faults may be easier to find with the help of gdb. http://sourceware.org/gdb/current/onlinedocs/gdb toc.html - online manual GDB Tutorial Additional step when compiling program Normally, you would compile a program like: gcc [flags] <source files> -o <output file> For example: gcc -Wall -Werror -ansi -pedantic-errors prog1.c -o prog1.x Now you add a -g option to enable built-in debugging support (which gdb needs): gcc [other flags] -g <source files> -o <output file> For example: gcc -Wall -Werror -ansi -pedantic-errors -g prog1.c -o prog1.x GDB Tutorial Starting up gdb Just try “gdb” or “gdb prog1.x.” You’ll get a prompt that looks like this: (gdb) If you didn’t specify a program to debug, you’ll have to load it in now: (gdb) file prog1.x Here, prog1.x is the program you want to load, and “file” is the command to load it. GDB Tutorial Before we go any further gdb has an interactive shell, much like the one you use as soon as you log into the linux grace machines. It can recall history with the arrow keys, auto-complete words (most of the time) with the TAB key, and has other nice features. Tip If you’re ever confused about a command or just want more information, use the “help” command, with or without an argument: (gdb) help [command] You should get a nice description and maybe some more useful tidbits.
    [Show full text]