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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.
Making Variable Value Changes Permanent
When you change an environment variable, that change only occurs in that
particular environment; in this case, that environment is the bash shell
session. This means that when you close the terminal, any changes you
made are lost, with values set back to their defaults. If you want to make the
changes permanent, you need to use the
export
command. This command
will
export the new value from your current environment (the bash shell) to
any new forked child processes. This allows the new process to inherit the
exported variables.
Variables are strings, so if you run on the cautious side, it isn’t a bad
idea to save the contents of a variable to a text file before you modify it.
For example, since we’re about to change the
PS1
variable, which controls
the information you display in the prompt, first run the following com-
mand to save the existing values to a text file in the current user’s home
directory:
kali >
echo $HISTSIZE> ~/valueofHISTSIZE.txt
This way, you can always undo your changes. If you want to be even
more cautious and create a text file with all the current settings, you can
save the output of the
set
command to a text file with a command like
this one:
kali >
set> ~/valueofALLon01012019.txt
After you’ve changed a variable, as we did in Listing 7-1, you can make
the change permanent by entering
export
and then the name of the variable
you changed, as shown here:
kali >
export HISTSIZE
Now the
HISTSIZE
variable will still be set to 0 in this environment and
will no longer store your commands. If you want to reset the
HISTSIZE
vari-
able to 1,000, simply enter this:
kali >
