clear history from shell

[Tom H]

On Mon, May 16, 2016 at 3:57 PM, Karl Auer <kauer at biplane.com.au> wrote:
> On Mon, 2016-05-16 at 13:18 +0100, Grizzly wrote:
>>
>> I have a simple script,
>>
>> #!/bin/sh
>> history -c && history -w && exit
>>
>> each part was tested manually and the whole line has also been
>> tested, but once I run the script it returns
>>
>> "3: Scripts/myclean.sh: history: not found"
>
> You changed the shell from bash (or dash) to sh in the first line of
> your script. Change it to /bin/bash and your script will run.

sh is dash by default in Ubuntu and, you're right, it dosen't have the
bash "history" builtin. Changing the shebang will fix the problem.

I don't use this command so I looked it up:

$ help history
history: history [-c] [-d offset] [n] or history -anrw [filename] or
history -ps arg [arg...]
 Display or manipulate the history list.

 Display the history list with line numbers, prefixing each modified
 entry with a `*'. An argument of N lists only the last N entries.

 Options:
 -c clear the history list by deleting all of the entries
 -d offset delete the history entry at offset OFFSET.
 -a append history lines from this session to the history file
 -n read all history lines not already read from the history file
 -r read the history file and append the contents to the history
  list
 -w write the current history to the history file
  and append them to the history list
 -p perform history expansion on each ARG and display the result
  without storing it in the history list
 -s append the ARGs to the history list as a single entry

 If FILENAME is given, it is used as the history file. Otherwise,
 if $HISTFILE has a value, that is used, else ~/.bash_history.

 If the $HISTTIMEFORMAT variable is set and not null, its value is used
 as a format string for strftime(3) to print the time stamp associated
 with each displayed history entry. No time stamps are printed otherwise.

 Exit Status:
 Returns success unless an invalid option is given or an error occurs.

Is "history -w" necessary?