| 1 | .\" Copyright 1991, 1999 Free Software Foundation, Inc. |
| 2 | .\" See section COPYING for conditions for redistribution |
| 3 | .\" $Id$ |
| 4 | .TH gdb 1 "4nov1991" "GNU Tools" "GNU Tools" |
| 5 | .SH NAME |
| 6 | gdb \- The GNU Debugger |
| 7 | .SH SYNOPSIS |
| 8 | .na |
| 9 | .TP |
| 10 | .B gdb |
| 11 | .RB "[\|" \-help "\|]" |
| 12 | .RB "[\|" \-nx "\|]" |
| 13 | .RB "[\|" \-q "\|]" |
| 14 | .RB "[\|" \-batch "\|]" |
| 15 | .RB "[\|" \-cd=\c |
| 16 | .I dir\c |
| 17 | \|] |
| 18 | .RB "[\|" \-f "\|]" |
| 19 | .RB "[\|" "\-b\ "\c |
| 20 | .IR bps "\|]" |
| 21 | .RB "[\|" "\-tty="\c |
| 22 | .IR dev "\|]" |
| 23 | .RB "[\|" "\-s "\c |
| 24 | .I symfile\c |
| 25 | \&\|] |
| 26 | .RB "[\|" "\-e "\c |
| 27 | .I prog\c |
| 28 | \&\|] |
| 29 | .RB "[\|" "\-se "\c |
| 30 | .I prog\c |
| 31 | \&\|] |
| 32 | .RB "[\|" "\-c "\c |
| 33 | .I core\c |
| 34 | \&\|] |
| 35 | .RB "[\|" "\-x "\c |
| 36 | .I cmds\c |
| 37 | \&\|] |
| 38 | .RB "[\|" "\-d "\c |
| 39 | .I dir\c |
| 40 | \&\|] |
| 41 | .RB "[\|" \c |
| 42 | .I prog\c |
| 43 | .RB "[\|" \c |
| 44 | .IR core \||\| procID\c |
| 45 | \&\|]\&\|] |
| 46 | .ad b |
| 47 | .SH DESCRIPTION |
| 48 | The purpose of a debugger such as GDB is to allow you to see what is |
| 49 | going on ``inside'' another program while it executes\(em\&or what another |
| 50 | program was doing at the moment it crashed. |
| 51 | |
| 52 | GDB can do four main kinds of things (plus other things in support of |
| 53 | these) to help you catch bugs in the act: |
| 54 | |
| 55 | .TP |
| 56 | \ \ \ \(bu |
| 57 | Start your program, specifying anything that might affect its behavior. |
| 58 | |
| 59 | .TP |
| 60 | \ \ \ \(bu |
| 61 | Make your program stop on specified conditions. |
| 62 | |
| 63 | .TP |
| 64 | \ \ \ \(bu |
| 65 | Examine what has happened, when your program has stopped. |
| 66 | |
| 67 | .TP |
| 68 | \ \ \ \(bu |
| 69 | Change things in your program, so you can experiment with correcting the |
| 70 | effects of one bug and go on to learn about another. |
| 71 | .PP |
| 72 | |
| 73 | You can use GDB to debug programs written in C, C++, and Modula-2. |
| 74 | Fortran support will be added when a GNU Fortran compiler is ready. |
| 75 | |
| 76 | GDB is invoked with the shell command \c |
| 77 | .B gdb\c |
| 78 | \&. Once started, it reads |
| 79 | commands from the terminal until you tell it to exit with the GDB |
| 80 | command \c |
| 81 | .B quit\c |
| 82 | \&. You can get online help from \c |
| 83 | .B gdb\c |
| 84 | \& itself |
| 85 | by using the command \c |
| 86 | .B help\c |
| 87 | \&. |
| 88 | |
| 89 | You can run \c |
| 90 | .B gdb\c |
| 91 | \& with no arguments or options; but the most |
| 92 | usual way to start GDB is with one argument or two, specifying an |
| 93 | executable program as the argument: |
| 94 | .sp |
| 95 | .br |
| 96 | gdb\ program |
| 97 | .br |
| 98 | .sp |
| 99 | |
| 100 | You can also start with both an executable program and a core file specified: |
| 101 | .sp |
| 102 | .br |
| 103 | gdb\ program\ core |
| 104 | .br |
| 105 | .sp |
| 106 | |
| 107 | You can, instead, specify a process ID as a second argument, if you want |
| 108 | to debug a running process: |
| 109 | .sp |
| 110 | .br |
| 111 | gdb\ program\ 1234 |
| 112 | .br |
| 113 | .sp |
| 114 | |
| 115 | would attach GDB to process \c |
| 116 | .B 1234\c |
| 117 | \& (unless you also have a file |
| 118 | named `\|\c |
| 119 | .B 1234\c |
| 120 | \&\|'; GDB does check for a core file first). |
| 121 | |
| 122 | Here are some of the most frequently needed GDB commands: |
| 123 | .TP |
| 124 | .B break \fR[\|\fIfile\fB:\fR\|]\fIfunction |
| 125 | \& |
| 126 | Set a breakpoint at \c |
| 127 | .I function\c |
| 128 | \& (in \c |
| 129 | .I file\c |
| 130 | \&). |
| 131 | .TP |
| 132 | .B run \fR[\|\fIarglist\fR\|] |
| 133 | Start your program (with \c |
| 134 | .I arglist\c |
| 135 | \&, if specified). |
| 136 | .TP |
| 137 | .B bt |
| 138 | Backtrace: display the program stack. |
| 139 | .TP |
| 140 | .BI print " expr"\c |
| 141 | \& |
| 142 | Display the value of an expression. |
| 143 | .TP |
| 144 | .B c |
| 145 | Continue running your program (after stopping, e.g. at a breakpoint). |
| 146 | .TP |
| 147 | .B next |
| 148 | Execute next program line (after stopping); step \c |
| 149 | .I over\c |
| 150 | \& any |
| 151 | function calls in the line. |
| 152 | .TP |
| 153 | .B step |
| 154 | Execute next program line (after stopping); step \c |
| 155 | .I into\c |
| 156 | \& any |
| 157 | function calls in the line. |
| 158 | .TP |
| 159 | .B help \fR[\|\fIname\fR\|] |
| 160 | Show information about GDB command \c |
| 161 | .I name\c |
| 162 | \&, or general information |
| 163 | about using GDB. |
| 164 | .TP |
| 165 | .B quit |
| 166 | Exit from GDB. |
| 167 | .PP |
| 168 | For full details on GDB, see \c |
| 169 | .I |
| 170 | Using GDB: A Guide to the GNU Source-Level Debugger\c |
| 171 | \&, by Richard M. Stallman and Roland H. Pesch. The same text is available online |
| 172 | as the \c |
| 173 | .B gdb\c |
| 174 | \& entry in the \c |
| 175 | .B info\c |
| 176 | \& program. |
| 177 | .SH OPTIONS |
| 178 | Any arguments other than options specify an executable |
| 179 | file and core file (or process ID); that is, the first argument |
| 180 | encountered with no |
| 181 | associated option flag is equivalent to a `\|\c |
| 182 | .B \-se\c |
| 183 | \&\|' option, and the |
| 184 | second, if any, is equivalent to a `\|\c |
| 185 | .B \-c\c |
| 186 | \&\|' option if it's the name of a file. Many options have |
| 187 | both long and short forms; both are shown here. The long forms are also |
| 188 | recognized if you truncate them, so long as enough of the option is |
| 189 | present to be unambiguous. (If you prefer, you can flag option |
| 190 | arguments with `\|\c |
| 191 | .B +\c |
| 192 | \&\|' rather than `\|\c |
| 193 | .B \-\c |
| 194 | \&\|', though we illustrate the |
| 195 | more usual convention.) |
| 196 | |
| 197 | All the options and command line arguments you give are processed |
| 198 | in sequential order. The order makes a difference when the |
| 199 | `\|\c |
| 200 | .B \-x\c |
| 201 | \&\|' option is used. |
| 202 | |
| 203 | .TP |
| 204 | .B \-help |
| 205 | .TP |
| 206 | .B \-h |
| 207 | List all options, with brief explanations. |
| 208 | |
| 209 | .TP |
| 210 | .BI "\-symbols=" "file"\c |
| 211 | .TP |
| 212 | .BI "\-s " "file"\c |
| 213 | \& |
| 214 | Read symbol table from file \c |
| 215 | .I file\c |
| 216 | \&. |
| 217 | |
| 218 | .TP |
| 219 | .B \-write |
| 220 | Enable writing into executable and core files. |
| 221 | |
| 222 | .TP |
| 223 | .BI "\-exec=" "file"\c |
| 224 | .TP |
| 225 | .BI "\-e " "file"\c |
| 226 | \& |
| 227 | Use file \c |
| 228 | .I file\c |
| 229 | \& as the executable file to execute when |
| 230 | appropriate, and for examining pure data in conjunction with a core |
| 231 | dump. |
| 232 | |
| 233 | .TP |
| 234 | .BI "\-se=" "file"\c |
| 235 | \& |
| 236 | Read symbol table from file \c |
| 237 | .I file\c |
| 238 | \& and use it as the executable |
| 239 | file. |
| 240 | |
| 241 | .TP |
| 242 | .BI "\-core=" "file"\c |
| 243 | .TP |
| 244 | .BI "\-c " "file"\c |
| 245 | \& |
| 246 | Use file \c |
| 247 | .I file\c |
| 248 | \& as a core dump to examine. |
| 249 | |
| 250 | .TP |
| 251 | .BI "\-command=" "file"\c |
| 252 | .TP |
| 253 | .BI "\-x " "file"\c |
| 254 | \& |
| 255 | Execute GDB commands from file \c |
| 256 | .I file\c |
| 257 | \&. |
| 258 | |
| 259 | .TP |
| 260 | .BI "\-directory=" "directory"\c |
| 261 | .TP |
| 262 | .BI "\-d " "directory"\c |
| 263 | \& |
| 264 | Add \c |
| 265 | .I directory\c |
| 266 | \& to the path to search for source files. |
| 267 | .PP |
| 268 | |
| 269 | .TP |
| 270 | .B \-nx |
| 271 | .TP |
| 272 | .B \-n |
| 273 | Do not execute commands from any `\|\c |
| 274 | .B .gdbinit\c |
| 275 | \&\|' initialization files. |
| 276 | Normally, the commands in these files are executed after all the |
| 277 | command options and arguments have been processed. |
| 278 | |
| 279 | |
| 280 | .TP |
| 281 | .B \-quiet |
| 282 | .TP |
| 283 | .B \-q |
| 284 | ``Quiet''. Do not print the introductory and copyright messages. These |
| 285 | messages are also suppressed in batch mode. |
| 286 | |
| 287 | .TP |
| 288 | .B \-batch |
| 289 | Run in batch mode. Exit with status \c |
| 290 | .B 0\c |
| 291 | \& after processing all the command |
| 292 | files specified with `\|\c |
| 293 | .B \-x\c |
| 294 | \&\|' (and `\|\c |
| 295 | .B .gdbinit\c |
| 296 | \&\|', if not inhibited). |
| 297 | Exit with nonzero status if an error occurs in executing the GDB |
| 298 | commands in the command files. |
| 299 | |
| 300 | Batch mode may be useful for running GDB as a filter, for example to |
| 301 | download and run a program on another computer; in order to make this |
| 302 | more useful, the message |
| 303 | .sp |
| 304 | .br |
| 305 | Program\ exited\ normally. |
| 306 | .br |
| 307 | .sp |
| 308 | |
| 309 | (which is ordinarily issued whenever a program running under GDB control |
| 310 | terminates) is not issued when running in batch mode. |
| 311 | |
| 312 | .TP |
| 313 | .BI "\-cd=" "directory"\c |
| 314 | \& |
| 315 | Run GDB using \c |
| 316 | .I directory\c |
| 317 | \& as its working directory, |
| 318 | instead of the current directory. |
| 319 | |
| 320 | .TP |
| 321 | .B \-fullname |
| 322 | .TP |
| 323 | .B \-f |
| 324 | Emacs sets this option when it runs GDB as a subprocess. It tells GDB |
| 325 | to output the full file name and line number in a standard, |
| 326 | recognizable fashion each time a stack frame is displayed (which |
| 327 | includes each time the program stops). This recognizable format looks |
| 328 | like two `\|\c |
| 329 | .B \032\c |
| 330 | \&\|' characters, followed by the file name, line number |
| 331 | and character position separated by colons, and a newline. The |
| 332 | Emacs-to-GDB interface program uses the two `\|\c |
| 333 | .B \032\c |
| 334 | \&\|' characters as |
| 335 | a signal to display the source code for the frame. |
| 336 | |
| 337 | .TP |
| 338 | .BI "\-b " "bps"\c |
| 339 | \& |
| 340 | Set the line speed (baud rate or bits per second) of any serial |
| 341 | interface used by GDB for remote debugging. |
| 342 | |
| 343 | .TP |
| 344 | .BI "\-tty=" "device"\c |
| 345 | \& |
| 346 | Run using \c |
| 347 | .I device\c |
| 348 | \& for your program's standard input and output. |
| 349 | .PP |
| 350 | |
| 351 | .SH "SEE ALSO" |
| 352 | .RB "`\|" gdb "\|'" |
| 353 | entry in |
| 354 | .B info\c |
| 355 | \&; |
| 356 | .I |
| 357 | Using GDB: A Guide to the GNU Source-Level Debugger\c |
| 358 | , Richard M. Stallman and Roland H. Pesch, July 1991. |
| 359 | .SH COPYING |
| 360 | Copyright (c) 1991 Free Software Foundation, Inc. |
| 361 | .PP |
| 362 | Permission is granted to make and distribute verbatim copies of |
| 363 | this manual provided the copyright notice and this permission notice |
| 364 | are preserved on all copies. |
| 365 | .PP |
| 366 | Permission is granted to copy and distribute modified versions of this |
| 367 | manual under the conditions for verbatim copying, provided that the |
| 368 | entire resulting derived work is distributed under the terms of a |
| 369 | permission notice identical to this one. |
| 370 | .PP |
| 371 | Permission is granted to copy and distribute translations of this |
| 372 | manual into another language, under the above conditions for modified |
| 373 | versions, except that this permission notice may be included in |
| 374 | translations approved by the Free Software Foundation instead of in |
| 375 | the original English. |