Tech Tip: Use History Expansion To Save Time and Typing
Most shells maintain a history of the commands that you've typed and that history can be used to save time and typing. Most of us have probably used the up/down arrow keys already to move through the list of commands that we've already entered, but there are other ways to access the data in the history list.
Let's say you want to install a package (we'll use a Debian/Ubuntu-based system as an example), so you type:
$ apt-get install packagename
But wait a minute, you need 'sudo' to do that! So what do you do? Retype the entire command again? No, use history expansion and type:
$ sudo !!
This will run the entire last command with 'sudo' prepended to it!
Let's take another example, say you want to list a directory's contents before changing into it, so you use ls to see the directory:
$ ls /usr/share/doc
Now, rather than typing the entire path name again as an argument to cd command, you simply type:
$ cd !$
This takes the last argument from the the last command entered and inserts it in the new command (use !* to include all the arguments from the last command).
Most shells provide many more expansion features that can save time and typing, check your shell's documentation for more information. For bash search for "History Expansion" or "Event Designators".
-- Regards, Matthew Cengia
Practical books for the most technical people on the planet. Newly available books include:
- Agile Product Development by Ted Schmidt
- Improve Business Processes with an Enterprise Job Scheduler by Mike Diehl
- Finding Your Way: Mapping Your Network to Improve Manageability by Bill Childers
- DIY Commerce Site by Reven Lerner
Plus many more.
- Happy GPL Birthday VLC!
- Handheld Emulation: Achievement Unlocked!
- Download "Linux Management with Red Hat Satellite: Measuring Business Impact and ROI"
- Unikernels, Docker, and Why You Should Care
- Giving Silos Their Due
- Controversy at the Linux Foundation
- New Products
- Don't Burn Your Android Yet
- Non-Linux FOSS: Snk
- Firefox OS