Want to protect your cyber security and still get fast solutions? Ask a secure question today.Go Premium

x
?
Solved

what does this command mean "history -d $((HISTCMD-1))"

Posted on 2014-09-16
2
Medium Priority
?
467 Views
Last Modified: 2014-09-16
from the command history, I see a command like this:

history -d $((HISTCMD-1))

I don't understand what this command does, could you please help.

thanks.
0
Comment
Question by:Jason Yu
2 Comments
 
LVL 68

Accepted Solution

by:
woolmilkporc earned 2000 total points
ID: 40326528
history is a command to manipulate the command line history.

Its "-d" flag is used to delete a command at a specific position (offset).

HISTCMD is a variable containing the future sequence number of the next command.

$(( )) is a shell construct to perform arithmetic operations.

So your command will delete the "current" entry from the shell's history, i. e. the "history -d ..." command itself - for whatever it's worth.
0
 

Author Comment

by:Jason Yu
ID: 40326702
thank you very much, I got it. it's the user wanting to hide his commands.
0

Featured Post

What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Fine Tune your automatic Updates for Ubuntu / Debian
In the first part of this tutorial we will cover the prerequisites for installing SQL Server vNext on Linux.
Learn several ways to interact with files and get file information from the bash shell. ls lists the contents of a directory: Using the -a flag displays hidden files: Using the -l flag formats the output in a long list: The file command gives us mor…
Learn how to get help with Linux/Unix bash shell commands. Use help to read help documents for built in bash shell commands.: Use man to interface with the online reference manuals for shell commands.: Use man to search man pages for unknown command…
Suggested Courses
Course of the Month13 days, 7 hours left to enroll

580 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question