Handling Folders and Files with Linux command Line[part2]

In the previous part I just explained 3 commands that will help you to navigate through files and folders in your system.In this section let us discuss how to perform some actions like create, rename, remove folders using command line.
Creating a folder using the command:
The command used to create a folder is mkdir .Open up the terminal and type :
                              
                                 mkdir myfolder

 A new folder named myfolder will be there in your home directory.You can make folders anywhere in your system.But you must mention the directory address for your folder with folder name otherwise the folder will be created in the current directory.
Eg: to make a folder in the directory /tmp use the following command.

                                 mkdir /tmp/myfolder


Extra note : Normally your system will not display any message after creation of the folder. If you add the parameter -v to the mkdir command you will get a message after the creation of the folder (eg: mkdir myfolder -v)
Removing a file or folder
The Linux kernel consider folder and file as same .You can remove any file or folder using the command rm .
the usage of the command is rm  [option]  <file> .
Here are the important options you might use.
 -f    (forcefully removes file with no prompting)
 -v   (Explains what is being done)
 -r   (Removes files recursively in a directory.It is used when the folder contains subfolders.)
I just mentioned the syntax above. But you need just a single command to remove a folder that is
             rm  -rf  /tmp/myfolder

here '-rf' is the option with the command which says that files will be removed recursively and forcefully. And /tmp/myfolder will be the folder we want to delete.

Know the amount of available Disk Space in Linux

We are already know that the Linux shell is the powerful tool which is capable of doing any jobs related with Linux OS .Read more about Linux terminalclick here .Here in this post I am going to tell about a simple command which is used to know the free space available in the hard disk partitions with in no time.

To get started open up the  terminal and  :

• Type df you can see the list of partitions with available free space listed.
• Type df -a to get a detailed listing of free space. this Include in the listing file-systems that have a size of 0 blocks, which are omitted by default.
• Type df -h to get a listing more optimized .Here size is listed in MBs .-h stands for human readable form .

To get the detailed syntax information use the command man df. This will list all the possibilities of the command.

Searching strings with grep command

Let me discuss a situation- I have saved all of my contacts information as separate files and put it in a folder called contacts. I have to find the file which contain the name Mr. John. I get started with opening each files in my text editor and ctr+f to find john..it was too difficult since I have about 300 files to search. But working a little smart I found john in 2 minutes..How ? The grep command .
 Grep is a command-line text-search utility originally written for Unix. The name comes from the ed command g/re/p (global / regular expression / print). The grep command searches the given file for lines containing a match to the given strings or words. grep displays the matching lines by default.
How to use grep command :
1.Searching for a string in a file

                $ grep train vehicles.txt

    the above usage will print all the lines containing the text train from vehicles.txt

2 .Searching in multiple files of same type :

                $ grep train *.txt

    the above command will print all the lines with text 'train' from all the text files in that folder

3. Searching by ignoring case sensitivity (with parameter -i)

                $ grep -i train vehicles.txt

     the above command will search all the 'train' sequences wihtout matching the cases.

4 . Word search

                $ grep -w train vehicles.txt

 

     Selecting all lines containing train as a word, i.e. surrounded' by white space (speedtrain
     and train  do not not match) may be accomplished with the -w option flag
5. Count lines when words are matched
             
                $ grep -c 'word' /directory


      grep can count the number of times that the pattern has been matched for each file using -c (count)    option.
6.Search recursively in an entire directory

               $ grep -r 'word' /directory  

   You can search recursively i.e. read all files under each directory for a string .