A useful technique to know about when using Linux is to run commands in the background. Sometimes certain commands can either take a while (like copying a large file) or will simply take over the terminal window when run. For example, lets say that you open a file in gedit, you might use the following command.
If you are part of a company the chances are that you have either set up or are aware of a backup policy for your data. However, even if you are not then you might have the need to backup certain items to a DVD drive.
The following shell command uses the find function to find all files in or below the current directory that have the extension php. It then passes each file found onto a sed command which then replaces all with the longer <?php version.
find . -name '*.php' -exec sed -ie 's##The -name argument in find will look at the base of the file name, that is, the file without any directory path. The -exec command is used to pass each file found onto another command, in this case sed is used.Much like using Alt+. to print out last parameter you can also use !$ to use the last parameter from the previous command. Here is a simple example.
This might sound odd, but this is a mnemonic that helps you remember a sequence of letters that you can enter when your Linux system is locked. This is a last ditch attempt to get things up and running again and should only be used if all else fails and the only other thing that you can do it pull the plug.
If you have also tried pressing Ctrl+Alt+backspace and this does nothing then you can try using the key sequence Raising Skinny Elephants Is Utterly Boring.
Searching for things in many files is easy with the grep command, but in order to view the results with the expression results highlighted you need to use grep in conjunction with less.
grep expression *.txt | less +/expression
If you wanted to search all files called something.txt for the letter d you would use this line.
grep d *.txt | less +/dA handy trick when using a Unix/Linux system is to repeat the last parameter from the previous line. Lets say that you typed in the following line to move a file to another directory.
$ mv file.txt /usr/local/
To then move into that directory you can just type cd and Alt+. to copy in the last parameter used in the last line. This will put the following on the command line.
If you sent a curl request to the slashdot.org server you get back a random Futurama quote contained within the header information. The following curl command:
curl -Is slashdot.org
The commands supplied are I and s. I causes only the header of the file to be shown and s stops curl printing out anything. This returns the following headers:
A fork bomb is a simple bit of shell code that, once run, will soon fill all available memory and fork space with itself. Here is the code, and remember, don't try this at home!
$ :(){ :|:& };:
To explain what is going on we need to cut this code into sections. The first thing we do is refine a function called ":", which accepts no parameters.
If you want to delete a file that you can't type in the name of either because the name is long and complicated, or because it is difficult to type in without causing a syntax error then here is the solution.
You first need to find the inode reference of the file. This can be done by using the command ls -li. The start of each line has a number that is specific to that file. You could use the command ls -i , but the output is a little confusing.