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How to enable timestamp in Linux History command

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<span style="color: #990000; font-family: verdana, geneva, sans-serif; font-size: large;"><span style="line-height: 26px;"><b><u>Enable timestamp in Linux History command</u></b></span></span><br />
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhc2QOOlsakpRCX3e3p71jw2KEK5nTzWbXpJOPsemKvg18bx_voXfdYvWO1_O7S07v3oXpH8MF6gn0tRlk9XOcVnO4AC5vqdxW6qROhAIXXGarle9Ih2qExtca6rqhJqRtPYKXWCDDAi8a0/s1600/linux-command_www.hackthesec.co.in.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="297" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhc2QOOlsakpRCX3e3p71jw2KEK5nTzWbXpJOPsemKvg18bx_voXfdYvWO1_O7S07v3oXpH8MF6gn0tRlk9XOcVnO4AC5vqdxW6qROhAIXXGarle9Ih2qExtca6rqhJqRtPYKXWCDDAi8a0/s320/linux-command_www.hackthesec.co.in.jpg" width="320" /></a><span style="color: #333333; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px; line-height: 26px;">The Bash history feature is an invaluable tool which allows users to recall commands previously entered into their shell with relative ease. This makes it easy to enter repeated commands and keep track of what was done on a system. By default, however, a user is unable to see whenthese commands were actually entered. When auditing a system, it can sometimes be useful to see this type of information, for example when trying to determine how and when a file may have gone missing on the file system. Since Bash version 3, however, you are able to enable time-stamping of entries for review later.</span></span><br />
<span style="color: #333333; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px; line-height: 26px;"><br /></span></span>
<span style="color: #333333; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px; line-height: 26px;">Applicable versions of Bash provide the environment variable HISTTIMEFORMAT which you can set for this purpose. Although it is empty by default, you can simple assign a time format string to enable time-stamping.</span></span><br />
<span style="background-color: white; font-size: 15px; line-height: 26px;"><span style="color: #0b5394; font-family: verdana, geneva, sans-serif;"><b><u>Enable timestamp in bash history</u></b></span></span><br />
<span style="background-color: white; font-size: 15px; line-height: 26px;"><span style="color: #333333; font-family: verdana, geneva, sans-serif;">To enable time stamp on your bash history type following command on your terminal:</span></span><br />
<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; color: white; font-family: monospace, serif; font-size: 14px; line-height: 19.2px; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;">$ export HISTTIMEFORMAT="%F %T "</pre>
<span style="background-color: white; font-size: 15px; line-height: 26px;"><span style="color: #333333; font-family: verdana, geneva, sans-serif;">Now execute</span></span><br />
<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; color: white; font-family: monospace, serif; font-size: 14px; line-height: 19.2px; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;">$ history</pre>
<span style="background-color: white; font-size: 15px; line-height: 26px;"><span style="color: #333333; font-family: verdana, geneva, sans-serif;">It will print the command line history with corresponding timestamp when the command was executed.</span></span><br />
<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; color: white; font-family: monospace, serif; font-size: 14px; line-height: 19.2px; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;">$ # history
    1  2016-06-12 15:14:15 nmtui
    2  <span style="line-height: 19.2px;">2016-06-12</span><span style="line-height: 19.2px;"> 15:14:15 ping 8.8.8.8</span>
    3  <span style="line-height: 19.2px;">2016-06-12</span><span style="line-height: 19.2px;"> 15:32:24 export HISTTIMEFORMAT="%F %T "</span>
    4  <span style="line-height: 19.2px;">2016-06-12</span><span style="line-height: 19.2px;"> 15:32:26 history</span></pre>
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How to enable timestamp in Linux History command

Enable timestamp in Linux History command The Bash history feature is an invaluable tool which allows users to recall commands previously ...

How To Run Command In Background on Linux

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<span style="color: #990000;"><u><i>Run Command In Background on Linux</i></u></span></h2>
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<span style="font-family: Georgia, Times New Roman, serif; font-size: 16px; line-height: 28px;">A background process is the process which executes behind the scenes. These processes run without user intervention. There are various way to do it for example using & or nohup or screen command. The most popular and frequently used are & and nohup(</span><span style="background-color: transparent; line-height: 28px;"><span style="font-family: Georgia, Times New Roman, serif;"><span style="color: red;">nohup is a POSIX command to ignore the HUP (hangup) signal</span>)</span></span><span style="font-family: Georgia, 'Times New Roman', serif; font-size: 16px; line-height: 28px;">. Including of these two options this tutorial will also describes you to use of screen command.</span></div>
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<span style="color: #0b5394;">1. Using &</span></h2>
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<span style="font-family: Georgia, Times New Roman, serif;">On Linux/Unix based systems we can easily send any process in background by appending & in command.</span></div>
<pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); color: white; line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-size: large;">$ ls -l &
$ tar czf temp.tar.gz /tmp &</span><span style="font-size: 0.9em;">
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<span style="font-family: Georgia, Times New Roman, serif;">In this way if you start a command in background and exited from shell, then shell will kill this background process with SIGHUP signal.</span></div>
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<span style="color: #0b5394;">2. Using nohup</span></h2>
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<span style="font-family: Georgia, Times New Roman, serif;">To prevent termination of background processes after shell termination use nohup command. nohup command simply use at prefix of command like. All the output generated with commands will save in nohup.out file in current directory.</span></div>
<pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); color: white; line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-size: large;">$ nohup tar czf temp.tar.gz /tmp &
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<span style="color: #0b5394;">3. Using Screen</span></h2>
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<span style="font-family: Georgia, Times New Roman, serif;">Screen is better option for long running processes. Using screen you can simply get the same session running on remote server even after logout from ssh. For this test you can do the following</span></div>
<pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); color: white; line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-size: large;">$ screen
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<span style="font-family: Georgia, Times New Roman, serif;">Now start your process in background.</span></div>
<pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); color: white; line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-size: large;">$ tar czf temp.tar.gz /tmp &
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Let’s detach your screen session with keyboard shortcut <span style="color: #990000;">CTRL+a+d or ctrl+alt+d</span>. It will return you to command line. Now exit your ssh session and again connect system through ssh and execute following command to get old screen session running.</div>
<pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); color: white; line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-size: large;">$ screen -r

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How To Run Command In Background on Linux

Run Command In Background on Linux A background process is the process which executes behind the scenes. These processes run without us...