Linux - Shell History
zzh@ZZHPC:~$ cat .bash_history
zzh@ZZHPC:~$ echo $HISTFILESIZE ## in file
2000
zzh@ZZHPC:~$ echo $HISTSIZE ## in memory
1000
zzh@ZZHPC:~$ cat .bash_history
zzh@ZZHPC:~$ echo $HISTFILESIZE ## in file
2000
zzh@ZZHPC:~$ echo $HISTSIZE ## in memory
1000