bash HISTSIZE vs. HISTFILESIZE?

Question

What is the difference in HISTSIZE vs. HISTFILESIZE?

They are used to extend bash history beyond the default 500 lines.

There seems to

Answer 1

Building on top of what arturomp have said and in an effort to make it a bit clearer.

Assumming you have 2000-something long history..

~$ history
    1  sdf
    2  fghdfgjf
    3  fghfghdf
   ..  ..
 2027  78
 2028  57
 2029  yu45u

You can cut down what you are shown with HISTSIZE

~$ HISTSIZE=5
~$ history
 2026  546
 2027  78
 2028  56
 2029  yu45u
 2030  HISTSIZE=5

Now, no matter how many commands you type, only the last 5 will be recorded.

~$ ABC
~$ GGH
~$ GSDHFG
~$ JFDR
~$ ABSDDS
~$ AHFGHFD


~$ history
    1  sdf
    2  fghdfgjf
    3  fghfghdf
   ..  ..
 2028  56
 2029  yu45u
 2030  HISTSIZE=5
 2031  GGH
 2032  GSDHFG
 2033  JFDR
 2034  ABSDDS
 2035  AHFGHFD

We can clearly see that our first command ("ABC") is not in the history since only the last 5 commands were recorded.

Now, the total history is stored in a file (.bash_history) and you can alter how long this file gets with the HISTFILESIZE. For example with a 2033 HISTFILESIZE, in my case I would have this:

~$ history
    1  fghfghdf
    2  gegege
    3  gege
   ..  ..
 2028  HISTSIZE=5
 2029  GGH
 2030  GSDHFG
 2031  JFDR
 2032  ABSDDS
 2033  AHFGHFD