understandable linux tips, tricks and tutorials

When using the terminal, there are a lot of tricks and shortcuts that can make using the terminal much more efficient and pleasurable. I’ll list here some of the key ones that I use.

history

Often in a terminal, you end up repeating the same commands from time to time. There is a program that records each command you type into a terminal called history. However, typing history and then searching for a command is slow and tedious, and the antithesis of what this howto is about. For searching through recent commands, you can use the up arrow. This will cycle through previous commands in order, one at a time. However, this can get tedious if you’re looking for something you typed a while ago. There are better ways of doing this. ctrl+r will allow you to interactively search through history as you type in commands. Pressing ctrl+r at an empty command prompt will give you a prompt that looks like this:

(reverse-i-search)`':

You can then type in part of a previous command and commands from history that match what you’ve typed will start to appear on the command line. So if I’m at the ctrl+r prompt and type up I get:

(reverse-i-search)`up': cd .superkaramba/lwp/

If I keep typing and add d, then the recalled command changes to:

(reverse-i-search)`upd': sudo aptitude update

This will find the most recent command that matches the characters as you type them.

The other way to search history for a command is with the grep command. So if you want to find all commands where you’ve used install, then you would type:

matt@laptop:~$ history | grep install
20  sudo aptitude install slmodem
69  configure --prefix=/usr && make && sudo make install
70  ./configure --prefix=/usr && make && sudo make install
74  sudo aptitude install openoffice.org-common
107  sudo aptitude install basket
112  ./configure --prefix=/usr && make && sudo make install
342  sudo aptitude install caca
412  sudo aptitude install spamassassin
428  sudo aptitude install eric
488  sudo aptitude install avidemux
498  sudo aptitude install libmozjs-dev
505  history | grep install

This can be useful where ctrl+r is not calling up the command line you want because a more recent command matches what you are typing into ctrl+r, and you can’t get to the previous command you want.

tab completion

Tab completion allows you to quickly type in filenames and directory paths on the commandline. When on the command line, you can type the first part of a filename or another directory in the current directory, and then press the tab key, and the rest of the filename will be completed for you. There are a few caveats:

  • If there is more than one file or directory that matches what you’ve typed, tab completion will display all of the files that match what you’ve typed.
  • If you use kubuntu, tab completion is context sensitive. So if you start typing tar -zxpf fil and press tab expecting it to complete filename.tar.bz2, tab completion will fail, as a tar.bz2 file is not compatible with the -z argument, which expects a .tar.gz file. This can be annoying for files that do not have an extension, or the correct extension.

cd

There are a couple of tricks with the cd command that are useful:

matt@laptop:~/tmp/Babasse$ cd
matt@laptop:~$

cd on its own will put you back in your home directory.

matt@laptop:~$ cd -
/home/matt/tmp/Babasse
matt@laptop:~/tmp/Babasse

cd - will change to the previous directory.

2 Comments
  1. So, what “shell” does all this work with? I know ‘tab’ completion works for tcsh, but it’s ‘escape’ for csh, for example.

    Also, I know that in csh the ‘cd -’ doesn’t work all by itself. I had to do an alias to get that behavior.

    Also, when was this published? Tools change over time. Quite sad to not have a date on the article to know what era these commands are from (ie new, old in 10 years, etc).

    For features like this, you should really have a list of “supported shells” kind of like a javascript page that says “works with these browsers” or mentions that some shells do it one way and others do it a slightly different way.

  2. This can be useful where ctrl+r is not calling up the command line you want because a more recent command matches what you are typing into ctrl+r, and you can’t get to the previous command you want.
    ———————————————————-
    You can press ctrl+r again and again until get the command you want

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