Command history

The history builtin command can be used to display the command history:

to display the entire command history, type history ;
if you're only interested in the last N entries, type history | tail -N.

Its behavior can be changed via various local variables (see Variables below).

Ion's history file is located by default in $HOME/.local/share/ion/history.

Unlike other shells, Ion by default saves repeated commands only once:

# echo "Hello, world!"
Hello, world!
# true
# true
# false
# history
echo "Hello, world!"
true
false

The REPL provides the following useful shortcuts for history searching:

Ctrl + s => forward search history ;
Ctrl + r => reverse search history ;
Ctrl + f => accept autosuggestion ;
Ctrl + u => delete content ;
Ctrl + c => interrupt command .

Variables

The following local variables can be used to modify Ion's history behavior:

HISTFILE

The file into which the history should be saved. At Ion' startup, the history will be read from this file, and when it exits, the session's history will be appended to this file.

Default value: $HOME/.local/share/ion/history

HISTFILE_ENABLED

Whether the history should be read from/written into the file specified by HISTFILE.

Default value: 1

A value of 1 means yes, everything else means no.

HISTFILE_SIZE

The maximum number of lines kept in the history file when flushed from memory.

Default value: 100000

It is useless to set this to a higher value than HISTORY_SIZE. Ideally, those variables would have the same value, since this would otherwise result in loss of information on history write to disk, which might not be worth it given the nowadays cheap hardware space.

(Currently ignored)

HISTORY_IGNORE

Which commands should not be saved in the history.

Default value: [ no_such_command whitespace duplicates ]

Each element of the array can take one of the following options:

all
All commands are ignored, nothing will be saved in the history.
no_such_command
Commands which return NO_SUCH_COMMAND will not be saved in the history.
whitespace
Commands which start with a whitespace character will not be saved in the history.
regex:xxx
Where xxx is treated as a regular expression. Commands which match this regular expression will not be saved in the history.
duplicates
All preceding duplicate commands are removed/ignored from the history after a matching command is entered.

Specifying an empty array, means that all commands will be saved.

Notes

You can specify as many elements as you want.
Any invalid elements will be silently ignored. They will still be present in the array though.
You can also specify as many regular expressions as you want (each as a separate element).
However, note that any command that matches at least one element will be ignored.
(Currently, ) there is no way to specify commands which should always be saved.
When specifying regex:-elements, it is suggested to surround them with single-quotes (')
As all variables, HISTORY_IGNORE is not saved between sessions. It is suggested to set it via ions init file.

The let HISTORY_IGNORE = [ .. ] command itself is not effected except if the assignment command starts with a whitespace and the whitespace element is specified in this assignment.

See the following example:

# echo @HISTORY_IGNORE

# let HISTORY_IGNORE = [ all ] # saved
# let HISTORY_IGNORE = [ whitespace ] # saved
#  true # ignored
# let HISTORY_IGNORE = [  ] # saved
#  let HISTORY_IGNORE = [ whitespace ] # ignored
# history
echo @HISTORY_IGNORE
let HISTORY_IGNORE = [ all ] # saved
let HISTORY_IGNORE = [ whitespace ] # saved
let HISTORY_IGNORE = [  ] # saved

Examples

# let HISTORY_IGNORE = [ no_such_command ]
# true # saved
#  true # saved
# false # saved
# trulse # ignored

# let HISTORY_IGNORE = [ 'regex:.*' ] # behaves like 'all'
# true # ignored
#  true # ignored
# false # ignored
# trulse # ignored

Tip

I like to add regex:#ignore$ to my HISTORY_IGNORE. That way, whenever I want to ignore a command on the fly, I just need to add #ignore to the end of the line.

HISTORY_SIZE

The maximum number of lines contained in the command history in-memory.

Default value: 1000

Ideally, this value should be the same as HISTFILE_SIZE (see HISTFILE_SIZE for details).

(Currently ignored)

HISTORY_TIMESTAMP

Whether a corresponding timestamp should be recorded along with each command.

The timestamp is indicated with a # and is unformatted as the seconds since the unix epoch.

Default value: 0

Possible values are 0 (disabled) and 1 (enabled).

Ion Documentation