1GDB(1) GNU Development Tools GDB(1)
2
6 gdb - The GNU Debugger
7
9 gdb [-help] [-nh] [-nx] [-q] [-batch] [-cd=dir] [-f] [-b bps]
10 [-tty=dev] [-s symfile] [-e prog] [-se prog] [-c core] [-p procID]
11 [-x cmds] [-d dir] [prog|prog procID|prog core]
12
14 The purpose of a debugger such as GDB is to allow you to see what is
15 going on "inside" another program while it executes -- or what another
16 program was doing at the moment it crashed.
17 GDB can do four main kinds of things (plus other things in support of
19 these) to help you catch bugs in the act:
20 · Start your program, specifying anything that might affect its
22 behavior.
23 · Make your program stop on specified conditions.
25 · Examine what has happened, when your program has stopped.
27 · Change things in your program, so you can experiment with
29 correcting the effects of one bug and go on to learn about another.
30 You can use GDB to debug programs written in C, C@t{++}, Fortran and
32 Modula-2.
33 GDB is invoked with the shell command "gdb". Once started, it reads
35 commands from the terminal until you tell it to exit with the GDB
36 command "quit". You can get online help from GDB itself by using the
37 command "help".
38 You can run "gdb" with no arguments or options; but the most usual way
40 to start GDB is with one argument or two, specifying an executable
41 program as the argument:
42 gdb program
44 You can also start with both an executable program and a core file
46 specified:
47 gdb program core
49 You can, instead, specify a process ID as a second argument or use
51 option "-p", if you want to debug a running process:
52 gdb program 1234
54 gdb -p 1234
55 would attach GDB to process 1234. With option -p you can omit the
57 program filename.
58 Here are some of the most frequently needed GDB commands:
60 break [file:]function
62 Set a breakpoint at function (in file).
63 run [arglist]
65 Start your program (with arglist, if specified).
66 bt Backtrace: display the program stack.
68 print expr
70 Display the value of an expression.
71 c Continue running your program (after stopping, e.g. at a
73 breakpoint).
74 next
76 Execute next program line (after stopping); step over any function
77 calls in the line.
78 edit [file:]function
80 look at the program line where it is presently stopped.
81 list [file:]function
83 type the text of the program in the vicinity of where it is
84 presently stopped.
85 step
87 Execute next program line (after stopping); step into any function
88 calls in the line.
89 help [name]
91 Show information about GDB command name, or general information
92 about using GDB.
93 quit
95 Exit from GDB.
96 For full details on GDB, see Using GDB: A Guide to the GNU Source-Level
98 Debugger, by Richard M. Stallman and Roland H. Pesch. The same text is
99 available online as the "gdb" entry in the "info" program.
100
102 Any arguments other than options specify an executable file and core
103 file (or process ID); that is, the first argument encountered with no
104 associated option flag is equivalent to a -se option, and the second,
105 if any, is equivalent to a -c option if it's the name of a file. Many
106 options have both long and short forms; both are shown here. The long
107 forms are also recognized if you truncate them, so long as enough of
108 the option is present to be unambiguous. (If you prefer, you can flag
109 option arguments with + rather than -, though we illustrate the more
110 usual convention.)
111 All the options and command line arguments you give are processed in
113 sequential order. The order makes a difference when the -x option is
114 used.
115 -help
117 -h List all options, with brief explanations.
118 -symbols=file
120 -s file
121 Read symbol table from file file.
122 -write
124 Enable writing into executable and core files.
125 -exec=file
127 -e file
128 Use file file as the executable file to execute when appropriate,
129 and for examining pure data in conjunction with a core dump.
130 -se=file
132 Read symbol table from file file and use it as the executable file.
133 -core=file
135 -c file
136 Use file file as a core dump to examine.
137 -command=file
139 -x file
140 Execute GDB commands from file file.
141 -ex command
143 Execute given GDB command.
144 -directory=directory
146 -d directory
147 Add directory to the path to search for source files.
148 -nh Do not execute commands from ~/.gdbinit.
150 -nx
152 -n Do not execute commands from any .gdbinit initialization files.
153 -quiet
155 -q "Quiet". Do not print the introductory and copyright messages.
156 These messages are also suppressed in batch mode.
157 -batch
159 Run in batch mode. Exit with status 0 after processing all the
160 command files specified with -x (and .gdbinit, if not inhibited).
161 Exit with nonzero status if an error occurs in executing the GDB
162 commands in the command files.
163 Batch mode may be useful for running GDB as a filter, for example
165 to download and run a program on another computer; in order to make
166 this more useful, the message
167 Program exited normally.
169 (which is ordinarily issued whenever a program running under GDB
171 control terminates) is not issued when running in batch mode.
172 -cd=directory
174 Run GDB using directory as its working directory, instead of the
175 current directory.
176 -fullname
178 -f Emacs sets this option when it runs GDB as a subprocess. It tells
179 GDB to output the full file name and line number in a standard,
180 recognizable fashion each time a stack frame is displayed (which
181 includes each time the program stops). This recognizable format
182 looks like two \032 characters, followed by the file name, line
183 number and character position separated by colons, and a newline.
184 The Emacs-to-GDB interface program uses the two \032 characters as
185 a signal to display the source code for the frame.
186 -b bps
188 Set the line speed (baud rate or bits per second) of any serial
189 interface used by GDB for remote debugging.
190 -tty=device
192 Run using device for your program's standard input and output.
193
195 The full documentation for GDB is maintained as a Texinfo manual. If
196 the "info" and "gdb" programs and GDB's Texinfo documentation are
197 properly installed at your site, the command
198 info gdb
200 should give you access to the complete manual.
202 Using GDB: A Guide to the GNU Source-Level Debugger, Richard M.
204 Stallman and Roland H. Pesch, July 1991.
205
207 Copyright (c) 1988-2019 Free Software Foundation, Inc.
208 Permission is granted to copy, distribute and/or modify this document
210 under the terms of the GNU Free Documentation License, Version 1.3 or
211 any later version published by the Free Software Foundation; with the
212 Invariant Sections being "Free Software" and "Free Software Needs Free
213 Documentation", with the Front-Cover Texts being "A GNU Manual," and
214 with the Back-Cover Texts as in (a) below.
215 (a) The FSF's Back-Cover Text is: "You are free to copy and modify this
217 GNU Manual. Buying copies from GNU Press supports the FSF in
218 developing GNU and promoting software freedom."
219gdb-Fedora 8.3.50.20190824-25.fc312019-11-21 GDB(1)