Filtering for Particular Variables Although using
set
with
more
gives more manageable results than looking
through the huge chunk of variable names you get with
set
alone, it can still
be rather tedious if you’re looking for a particular variable. Instead, you can
use the filtering command
grep
to find your variable of interest.
Let’s use the variable
HISTSIZE
as an example. This variable contains
the maximum number of commands your command history file will store.
These commands are any ones you’ve previously typed into your command
prompt in this session and can be recalled with your up- and down-arrow
keys. Note that
HISTSIZE
doesn’t store the commands themselves, just the
number of them that can be stored.
Pipe your
set
output with
grep
to find the
HISTSIZE
variable, like so:
kali >set | grep HISTSIZE HISTSIZE=1000
As you can see, this command finds the variable
HISTSIZE
and displays
its value. The default value of this variable is probably set to
1000
on your
system. This indicates that the terminal will store your last 1,000 commands
by default.
Changing Variable Values for a Session Now let’s see how to change a variable’s value. As noted, the
HISTSIZE
variable
contains the value of the number of commands to store in the history file.
Sometimes, you won’t want your system to save past commands—perhaps
because you don’t want to leave any evidence of your activity on your own
system or a target system. In that case, you can set the
HISTSIZE
variable to
0
so the system won’t store any of your past commands. Because this variable
has a single value, to change it, you assign it a new value in the familiar way
shown in Listing 7-1.
kali >HISTSIZE=0 Listing 7-1: Changing the value of HISTSIZE
74 Chapter 7
Now, when you try to use the up- and down-arrow keys to recall your
commands, nothing happens because the system no longer stores them.
This is stealthy, although it can be inconvenient.
