How to hide your Linux command line history
Aug 17, 2024 am 07:34 AM
If you are a Linux command line user, sometimes you may not want certain commands to be recorded in your command line history. There could be many reasons, for example, you hold a certain position in a company and you have certain privileges that you don't want others to abuse. Or maybe there are some particularly important commands that you don't want to execute by mistake while browsing the history list.
However, is there a way to control which commands go into the history list and which don't? Or in other words, can we enable incognito mode like a browser in a Linux terminal? The answer is yes, and depending on the specific goals you want, there are many ways to achieve it. In this article, we’ll discuss some proven methods.
Note: All commands appearing in this article have been tested under Ubuntu.
The first two methods have been described in a previous article. If you already know this, you can skip this part. However, if you don't understand it, it is recommended to read it carefully.
Yes, you read that right. By inserting a space before the command, the command will be ignored by the shell, which means it will not appear in the history. But this method has a prerequisite. It will only work if your environment variable HISTCONTROL is set to "ignorespace" or "ignoreboth". In most cases, this is the default value.
So, like the following command (here [space] means entering a space):
[space]echo "this is a top secret"
If you have previously executed the following command to set environment variables, the above command will not appear in the history.
export HISTCONTROL = ignorespace
The screenshot below is an example of this approach.
The fourth "echo" command is not recorded in the history because there is a space in front of it.
If you want to disable all history for a session, you can simply clear the value of the environment variable HISTSIZE before starting command line work. Execute the following command to clear its value:
export HISTSIZE=0
HISTSIZE indicates the number of commands (number of lines) that can be saved in the history list of a bash session. By default it is set to a non-zero value, for example on my computer it is 1000.
So the above mentioned command sets its value to 0, with the result that nothing will be stored in the history until you close the terminal. Remember that you also cannot see previously executed commands by pressing the up arrow key or running the history command.
This can be seen as another implementation of the solution proposed in the previous part. The only difference is to execute this command after you have finished all your work. The following is the command just mentioned:
history -cw
As mentioned just now, this has the same effect as the HISTSIZE method.
While the previously described methods (2 and 3) will serve the purpose, they can clear the entire history, and in many cases some may not be what we expect. Sometimes you may want to save the history until you started working on the command line. For such needs, you start executing the following commands before working:
[space]set +o history
Note: [space] means space. And because of the spaces, the command itself is not logged either.
The above command will temporarily disable the history function, which means that all operations you perform after this command will not be recorded in the history, but everything before this command will be recorded in the history list as is.
To re-enable the history function, execute the following command:
[Space]set -o history
It will restore the environment to its original state, that is, you have completed your work, and the commands after executing the above command will appear in the history.
現(xiàn)在假設(shè)歷史記錄中已經(jīng)包含了一些你不希望記錄的命令。這種情況下我們?cè)趺崔k？很簡單。直接動(dòng)手刪除它們。通過下面的命令來刪除：
history | grep "part of command you want to remove"
上面的命令會(huì)輸出歷史記錄中匹配的命令，每一條前面會(huì)有個(gè)數(shù)字。
一旦你找到你想刪除的命令，執(zhí)行下面的命令，從歷史記錄中刪除那個(gè)指定的項(xiàng)：
history -d [num]
下面是這個(gè)例子的截圖。
第二個(gè) ‘echo’命令被成功的刪除了。
（如果你不希望上述命令本身也被記錄進(jìn)歷史中，你可以在上述命令前加個(gè)空格）
同樣的，你可以使用向上的箭頭一直往回翻看歷史記錄。當(dāng)你發(fā)現(xiàn)你感興趣的命令出現(xiàn)在終端上時(shí)，按下 “Ctrl + U”清除整行，也會(huì)從歷史記錄中刪除它。
有多種不同的方法可以操作 Linux 命令行歷史來滿足你的需求。然而請(qǐng)記住，從歷史中隱藏或者刪除命令通常不是一個(gè)好習(xí)慣，盡管本質(zhì)上這并沒有錯(cuò)。但是你必須知道你在做什么，以及可能產(chǎn)生的后果。
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