Linux Commands - mkdir | rmdir | touch | rm | cp | more | less | head | tail | cat

mkdir: Create Directory
rmdir: Remove Directory
touch: Create a file

rm:    Remove file
cp:    Copy file
more:  View file content <More than 1 page>
less:  View the file content
head:  Display first 10 lines of file
tail:  Display last 10 lines of file

mkdir:

User can create their directory using mkdir command.

Example:

hadoopguru@hadoop2:~$ mkdir hadoop_test
hadoopguru@hadoop2:~$ ls

apache-flume-1.4.0-bin.tar.gz.1            hadoop-1.2.1-bin.tar.gz

aveo                                       hadoop_test

data                                       hive

datanode                                   hive-0.11.0-bin.tar.gz

derby.log                                  mahout-distribution-0.8.tar.gz

flume                                      metastore_db

hadoop-1.2.1                               namenode

touch: 

Creating a file:

Creating a file can be done using touch command

Example:

hadoopguru@hadoop2:~$ cd hadoop_test/

hadoopguru@hadoop2:~/hadoop_test$ touch pig.txt

hadoopguru@hadoop2:~/hadoop_test$ touch hive.txt

hadoopguru@hadoop2:~/hadoop_test$ touch mahout

hadoopguru@hadoop2:~/hadoop_test$ ls -l

total 0

-rw-rw-r-- 1 hadoop hadoop 0 Oct 28 00:13 hive.txt

-rw-rw-r-- 1 hadoop hadoop 0 Oct 28 00:13 mahout

-rw-rw-r-- 1 hadoop hadoop 0 Oct 28 00:13 pig.txt

1.  touch –t :

One can create a new file with user defined date and time, using this touch -t command.

Example:

hadoopguru@hadoop2:~/hadoop_test$ touch -t 201310272350 testemp1

hadoopguru@hadoop2:~/hadoop_test$ ls -l

total 0

-rw-rw-r-- 1 hadoop hadoop 0 Oct 28  00:13   hive.txt

-rw-rw-r-- 1 hadoop hadoop 0 Oct 28  00:13   mahout

-rw-rw-r-- 1 hadoop hadoop 0 Oct 28  00:13   pig.txt

-rw-rw-r-- 1 hadoop hadoop 0 Oct 27  23:50   testemp

-rw-rw-r-- 1 hadoop hadoop 0 Oct 27  23:50   testemp1

rm: 

      Removing a file:

File can be removed using rm command.

Note: A file can’t be recovered back after remove. A file once removed is gone. Hence one should be careful before removing a file.

Example:

hadoopguru@hadoop2:~/hadoop_test$ ls

hive.txt  mahout  pig.txt  testemp  testemp1  testemp2

hadoopguru@hadoop2:~/hadoop_test$ rm testemp2

hadoopguru@hadoop2:~/hadoop_test$ ls

hive.txt  mahout  pig.txt  testemp  testemp1

      

      rm -i :

This command asks for a confirmation from user to remove a file.

Example:

hadoopguru@hadoop2:~/hadoop_test$ ls

hive.txt  mahout  pig.txt  testemp  testemp1

hadoopguru@hadoop2:~/hadoop_test$ rm -i testemp1

rm: remove regular empty file `testemp1'? y

hadoopguru@hadoop2:~/hadoop_test$ ls

hive.txt  mahout  pig.txt  testemp

      rm -r :

This command can be used to remove any file or directory.

Example:

test_dir is a directory which can be removed using rm –r command

hadoopguru@hadoop2:~/hadoop_test$ ls

hive.txt  mahout  pig.txt  test_dir  testemp  test_empty

hadoopguru@hadoop2:~/hadoop_test$ rm –r test_dir

hadoopguru@hadoop2:~/hadoop_test$ ls

hive.txt  mahout  pig.txt  testemp  test_empty

cp:

Copy a file:

In order to copy a file cp command is used.

If in case the target is a directory, the source file will get copied to that directory.

      Example

    1: Copy from file to file

hadoopguru@hadoop2:~/hadoop_test$ ls

hive.txt  pig.txt   testemp     Test_file1.txt

mahout    Test_dir  test_empty  Test_file2.txt

hadoopguru@hadoop2:~/hadoop_test$ cp Test_file1.txt Test_file2.txt

    2: Target is a directory

hadoopguru@hadoop2:~/hadoop_test$ cd Test_dir

hadoopguru@hadoop2:~/hadoop_test/Test_dir$ ls

hadoopguru@hadoop2:~/hadoop_test/Test_dir$ cd ..

hadoopguru@hadoop2:~/hadoop_test$ cp Test_file1.txt Test_dir

hadoopguru@hadoop2:~/hadoop_test$ cd Test_dir

hadoopguru@hadoop2:~/hadoop_test/Test_dir$ ls

Test_file1.txt

    3: If user wants to copy whole directory, cp -r command is used.

Example:

Case I:  If target directory doesnot exist

hadoopguru@hadoop2:~/hadoop_test$ ls

hive.txt    pig.txt      Test_dir2    Test_file1.txt

mahout      Test_dir     testemp      Test_file2.txt

hadoopguru@hadoop2:~/hadoop_test$ ls Test_dir

Test_file1.txt

hadoopguru@hadoop2:~/hadoop_test$ cp -r Test_dir Test_dir1

hadoopguru@hadoop2:~/hadoop_test$ ls

hive.txt    pig.txt      Test_dir1     testemp     Test_file2.txt

mahout      Test_dir     Test_dir2     Test_file1.txt

hadoopguru@hadoop2:~/hadoop_test$ ls Test_dir1/

Test_file1.txt

Case II:  If target directory already exist

hadoopguru@hadoop2:~/hadoop_test$ ls

hive.txt  pig.txt   Test_dir1  testemp         Test_file2.txt

mahout    Test_dir  Test_dir2  Test_file1.txt

hadoopguru@hadoop2:~/hadoop_test$ ls Test_dir1

Test_file1.txt

hadoopguru@hadoop2:~/hadoop_test$ ls Test_dir2

Test_file2.txt

hadoopguru@hadoop2:~/hadoop_test$ cp -r Test_dir1 Test_dir2

hadoopguru@hadoop2:~/hadoop_test$ ls Test_dir2

Test_dir1  Test_file2.txt

    4:  File(s) from one directory to another:

File can be copied from one directory to another using same cp command where last name will always be a directory name

Example:

Case I:  Copy single file

hadoopguru@hadoop2:~/hadoop_test$ ls

hive.txt  pig.txt   Test_dir1  testemp         Test_file2.txt

mahout    Test_dir  Test_dir2  Test_file1.txt

hadoopguru@hadoop2:~/hadoop_test$ ls Test_dir1

Test_file1.txt

hadoopguru@hadoop2:~/hadoop_test$ ls Test_dir2

Test_file2.txt

hadoopguru@hadoop2:~/hadoop_test$ cp Test_dir1/Test_file1.txt Test_dir2

hadoopguru@hadoop2:~/hadoop_test$ ls Test_dir2

Test_file1.txt  Test_file2.txt

Case II:  Copy multiple files 

hadoopguru@hadoop2:~/hadoop_test$ ls

hive.txt  pig.txt   Test_dir1  testemp         Test_file2.txt

mahout    Test_dir  Test_dir2  Test_file1.txt

hadoopguru@hadoop2:~/hadoop_test$ cp hive.txt pig.txt Test_dir1/Test_file1.txt Test_dir2

hadoopguru@hadoop2:~/hadoop_test$ ls Test_dir2

hive.txt  pig.txt  Test_file1.txt  Test_file2.txt

    5:  Interactive commands:

Interactive command (cp –i) ask user confirmation to overwrite the existing file.

Example:

hadoopguru@hadoop2:~/hadoop_test$ ls

hive.txt  mahout  pig.txt  Test_dir  Test_dir1  Test_dir2

hadoopguru@hadoop2:~/hadoop_test$ cp -i hive.txt mahout

cp: overwrite `mahout'? no

hadoopguru@hadoop2:~/hadoop_test$



more:

         more command is used to view the contents of a file containing more than 1 page. 

      Can scroll to the next page using Space bar or PageUp Pagedown buttons.

Example:

hadoop@hadoop2:~$ ls

AboutHadoop.txt   aveo  data  derby.log  hadoop-1.2.1             hadoop_test       hive-0.11.0-bin.tar.gz metastore_db

apache-flume-1.4.0-bin.tar.gz.1          count.txt 

datanode          flume       hadoop-1.2.1-bin.tar.gz  

hive              mahout-distribution-0.8.tar.gz  namenode

hadoop@hadoop2:~$ more AboutHadoop.txt

Hadoop is framework written in Java.

1.  Scalable fault tolerant distributed system for large data storage & processing.

2.  Designed to solve problems that involve storing, processing & analyzing large data (Terabytes, petabytes, etc.)

3.  Programming Model is based on Google's Map Reduce.

4.  Infrastructure based on Google's Big Data & distributed file system.

less:

      less is also a command to view file content. After viewing file press q to quit.

Example:  

hadoop@hadoop2:~$ less count.txt

Press enter

one

two

three

four

five

six

seven

eight

nine

ten

eleven

twelve

count.txt (END)
Type "q:" & <Hit Enter> to come out of this.

hadoop@hadoop2:~$

      Head: 

      

      Displays first ten lines of a file.

Example:

hadoop@hadoop2:~$ head count.txt

one

two

three

four

five

six

seven

eight

nine

ten

      Tail: 

      Displays last 10 lines of file

Example:

hadoop@hadoop2:~$ tail count.txt

three

four

five

six

seven

eight

nine

ten

eleven

twelve

More Commands: 

   head  –n or tail  -n : Displays n number of lines

   head –cn or tail –cn : Displays n no of bytes of file.

MORE LINUX COMMANDS

Linux Commands - pwd | cd | ls | mkdir | rmdir | pushd | popd | clear