2 Getting In and Out of GDB

This chapter discusses how to start GDB, and exit out of it. The essentials are:

•type '(gdb)' to start GDB.

•type quit or C-dto exit.

2.1Invoking GDB

Invoke GDB by running the program (gdb). Once started, GDB reads commands from the terminal until you tell it to exit.

You can also run (gdb) with a variety of arguments and options, to specify more of your debugging environment at the outset.

The command-line options described here are designed to cover a variety of situations; in some environments, some of these options may effectively be unavailable.

The most usual way to start GDB is with one argument, specifying an executable program:

(gdb) program

You can also start with both an executable program and a core file specified:

(gdb) program core

You can, instead, specify a process ID as a second argument, if you want to debug a running process:

(gdb) program 1234

would attach GDB to process 1234 (unless you also have a file named '1234'; GDB does check for a core file first).

Taking advantage of the second command-line argument requires a fairly complete operating system; when you use GDB as a remote debugger attached to a bare board, there may not be any notion of “process”, and there is often no way to get a core dump. GDB will warn you if it is unable to attach or to read core dumps.

You can run (gdb) without printing the front material, which describes GDB's non-warranty, by specifying -silent:

gdb -silent

You can further control how GDB starts up by using command-line options. GDB itself can remind you of the options available.

Type

(gdb) -help

to display all available options and briefly describe their use ('(gdb)-h' is a shorter equivalent).

2.1 Invoking GDB 25