Command history

General

  • Ions history can be found at $HOME/.local/share/ion/history
  • The history builtin can be used to display the entire command history
    • If you're only interested in the last X entries, use history | tail -n X
  • The histories' behavior can be changed via various local variables (see section Variables)
  • Unlike other shells, ion saves repeated commands only once:
# echo "Hello, world!"
Hello, world!
# true
# true
# false
# history
echo "Hello, world!"
true
false

Variables

The following local variables can be used to modify Ions history behavior:

HISTORY_SIZE

Determines how many entries of the history are kept in memory. Default value is 1000. Ideally, this value should be the same as HISTFILE_SIZE

HISTORY_IGNORE

Specifies which commands should NOT be saved in the history. This is an array and defaults to an empty array, meaning that all commands will be saved. 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.

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

Tips

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.

HISTFILE_ENABLED

Specifies whether the history should be read from/written into the file specified by HISTFILE. A value of 1 means yes, everything else means no. Defaults to 1.

HISTFILE

The file into which the history should be saved. At the launch of ion the history will be read from this file and when ion exits, the history of the session will be appended into the file. Defaults to $HOME/.local/share/ion/history

HISTFILE_SIZE

Specifies how many commands should be saved in HISTFILE at most. Ideally, this should have the same value as HISTORY_SIZE. Defaults to 100000.

HISTORY_TIMESTAMP

Specifies 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. This feature is disabled by default and can be enabled by executing the following command: let HISTORY_TIMESTAMP = 1.