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19.3 Command History

No value for GDBN can keep track of the commands you type during your debugging sessions, so that you can be certain of precisely what happened. Use these commands to manage the No value for GDBN command history facility.

No value for GDBN uses the GNU History library, a part of the Readline package, to provide the history facility. @xref{Using History Interactively}, for the detailed description of the History library.

To issue a command to No value for GDBN without affecting certain aspects of the state which is seen by users, prefix it with ‘server ’ (see section The Server Prefix). This means that this command will not affect the command history, nor will it affect No value for GDBN's notion of which command to repeat if <RET> is pressed on a line by itself.

The server prefix does not affect the recording of values into the value history; to print a value without recording it into the value history, use the output command instead of the print command.

Here is the description of No value for GDBN commands related to command history.

set history filename fname

Set the name of the No value for GDBN command history file to fname. This is the file where No value for GDBN reads an initial command history list, and where it writes the command history from this session when it exits. You can access this list through history expansion or through the history command editing characters listed below. This file defaults to the value of the environment variable GDBHISTFILE, or to ‘./.gdb_history’ (‘./_gdb_history’ on MS-DOS) if this variable is not set.

set history save
set history save on

Record command history in a file, whose name may be specified with the set history filename command. By default, this option is disabled.

set history save off

Stop recording command history in a file.

set history size size

Set the number of commands which No value for GDBN keeps in its history list. This defaults to the value of the environment variable HISTSIZE, or to 256 if this variable is not set.

History expansion assigns special meaning to the character !. @xref{Event Designators}, for more details.

Since ! is also the logical not operator in C, history expansion is off by default. If you decide to enable history expansion with the set history expansion on command, you may sometimes need to follow ! (when it is used as logical not, in an expression) with a space or a tab to prevent it from being expanded. The readline history facilities do not attempt substitution on the strings != and !(, even when history expansion is enabled.

The commands to control history expansion are:

set history expansion on
set history expansion

Enable history expansion. History expansion is off by default.

set history expansion off

Disable history expansion.

show history
show history filename
show history save
show history size
show history expansion

These commands display the state of the No value for GDBN history parameters. show history by itself displays all four states.

show commands

Display the last ten commands in the command history.

show commands n

Print ten commands centered on command number n.

show commands +

Print ten commands just after the commands last printed.

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