Is there any way to keep a command from being added to your history?

Question

Is there any way to keep a command from being added to your history? I have a command that I want to keep out of my history file, and I really don't care to have it there when I search the history stored in memory, though that's less of a concern. Is there any way to prevent this, or do I just have to go back and edit my history file.

update: I didn't realize this might be shell-specific. My shell is zsh. You're welcome to answer for other shells so people know how to do this in their shell.

Answer 1

In ZSH:

First set HIST_IGNORE_SPACE in your profile and then prefix the commands you don't want stored with a space.

From the man page, the following 3 options can be used to say that certain lines shouldn't go into the history at all

• HIST_IGNORE_SPACE don't store commands prefixed with a space
• HIST_NO_STORE don't store history (fc -l) command
  
• HIST_NO_FUNCTIONS don't store function definitions
  

Answer 2

If you're running the command over and over and your shell is bash, the HISTIGNORE variable will do this. Lets say you have secret.server.com that you ssh to, FTP files to, etc. that you don't want any line that mentions secret.server.com saved:

HISTIGNORE="*secret.server.com*"

You can list multiple patterns with a colon separating them. Make sure sure you include a * if needed since in the below example, 'fortune' would be excluded, but 'fortune -l' would included':

HISTIGNORE="*secret.server.com*:ytalk*:fortune"

With HISTIGNORE set, nothing matching the patterns you list will be saved to .bash_history and even the up arrow key, which normally recalls your previous command, won't work if it matches your pattern.

Answer 3

In bash, use the HISTCONTROL variable.

Set it to HISTCONTROL=ignorespace (or HISTCONTROL=ignoreboth). From now, when you begin a line with a space and it will not be saved in the history. This avoids to include the not-to-be-disclosed-command in some configuration file.

Even like that it happens to forget to add the space and then want to go back. To delete one entry in the history, use history -d <index>, with index the number found with the history command (first column).

Answer 4

The easiest way for a one-off is

$ $SHELL
$$ unset HISTFILE
$$ secret-command
$$ exit
$

where $ represents the prompt of the initial shell and $$ represents the prompt of the subshell. This works in bash and zsh; in ksh you need HISTFILE=/notwritable instead. Note that what matters is the value of HISTFILE when the history file is written, not when the command is run. Bash, ksh and zsh write to the history file when they exit (zsh can do it more often depending on configuration).

Alternatively, you can get bash or zsh to ignore lines matching certain patterns (this is already covered by other answers).

Another possibility in zsh is

% fc -p
% secret-command
% fc -P

fc -p pushes the current history list onto a stack and starts a new one that isn't associated with a save file. fc -P pops that unsaved history list off the stack and forgets about it altogether.

While a process is running, the command and its arguments (and on some systems its environment as well) will show up in the process table (ps output). Root can see past commands in the system accounting database, and can do more logging without your control. And there'll probably be all kinds of forensic evidence that can show roughly what command you ran (such as file modification times). So you don't get privacy against determined eavesdroppers.