A user-defined command is a sequence of gdb commands to
which you assign a new name as a command. This is done with the
define command. User commands may accept an unlimited number of arguments
separated by whitespace. Arguments are accessed within the user command
$arg0...$argN. A trivial example:
define adder print $arg0 + $arg1 + $arg2 end
To execute the command use:
adder 1 2 3
This defines the command
adder, which prints the sum of
its three arguments. Note the arguments are text substitutions, so they may
reference variables, use complex expressions, or even perform inferior
$argc may be used to find out how many arguments have
define adder if $argc == 2 print $arg0 + $arg1 end if $argc == 3 print $arg0 + $arg1 + $arg2 end end
Combining with the
eval command (see eval) makes it easier
to process a variable number of arguments:
define adder set $i = 0 set $sum = 0 while $i < $argc eval "set $sum = $sum + $arg%d", $i set $i = $i + 1 end print $sum end
The definition of the command is made up of other gdb command lines,
which are given following the
define command. The end of these
commands is marked by a line containing
help. The command commandname must already be defined. This command reads lines of documentation just as
definereads the lines of the command definition, ending with
end. After the
documentcommand is finished,
helpon command commandname displays the documentation you have written.
You may use the
document command again to change the
documentation of a command. Redefining the command with
does not change the documentation.
max-user-call-depthcontrols how many recursion levels are allowed in user-defined commands before gdb suspects an infinite recursion and aborts the command. This does not apply to user-defined python commands.
In addition to the above commands, user-defined commands frequently use control flow commands, described in Command Files.
When user-defined commands are executed, the commands of the definition are not printed. An error in any command stops execution of the user-defined command.
If used interactively, commands that would ask for confirmation proceed without asking when used inside a user-defined command. Many gdb commands that normally print messages to say what they are doing omit the messages when used in a user-defined command.