2.1 Invoking 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 or use option -p, if you want to debug a running process:

gdb program 1234
gdb -p 1234

would attach GDB to process 1234. With option -p you can omit the program filename.

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 optionally have gdb pass any arguments after the executable file to the inferior using --args. This option stops option processing.

gdb --args gcc -O2 -c foo.c

This will cause gdb to debug gcc, and to set gcc’s command-line arguments (see Arguments) to ‘-O2 -c foo.c’.

You can run gdb without printing the front material, which describes GDB’s non-warranty, by specifying --silent (or -q/--quiet):

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).

All options and command line arguments you give are processed in sequential order. The order makes a difference when the ‘-x’ option is used.