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Friday, 15 November 2013

Head and Tail Commands in Linux


Head Command

Description : prints output of first part of the file by default it will print first 10 lines

Syntax : head filename

examples:

1.  head upcasting.java


it will print first 10 lines of the file upcasting.java by default.

2. head -n 50 upcasting.java
 it will print first 50 lines of the file upcasting.java.

3. head upcasting.java downcasting.java
it will print first 10 line of the 2 files upcasting.java and downcasting.java.

4. head *.java
it will print all the java files first 10 lines.

5. head *.java *.class
it will print all the java and class files first 10 lines.


Tail Command:

Description : prints output of last part of the file by default it will print last 10 lines

Syntax : tail filename

Examples:

1. tail upcasting.java
it will print last 10 lines of the file upcasting.java by default.

2. tail -n 50 upcasting.java
 it will print last 50 lines of the file upcasting.java.

3. tail upcasting.java downcasting.java
it will print last 10 line of the 2 files upcasting.java and downcasting.java.

4. tail *.java
it will print all the java files last 10 lines.

5. tail *.java *.class
it will print all the java and class files last 10 lines.

Practice Examples:

1. How to Print the 11th line of the file ?

    head -n 11 upcasting.java | tail -n 1

2. How to print lines from 5 to 11th of the file ?

    head -n 11 upcasting.java | tail -n 5

3.  How to print number of lines head and tail command file (by default it will  print 10 lines)?
   
    head upcasting.java | wc -l
    tail upcasting.java | wc -l


    both will return 10

    head -n 20 upcasting.java | wc -l
    tail -n 20 upcasting.java | wc -l


   both will return 20

   for number of word wc -w and number of characters wc -c

   head upcasting.java | wc -c
   it will print number of first 10 lines characters in digits

   tail upcasting.java | wc -c
   it will print number of last 10 lines characters in digits
 

   head upcasting.java | wc -w
   it will print number of first 10 lines words in digits

   tail upcasting.java | wc -w
   it will print number of last 10 lines words in digits

4. How to get First and last 5 files of java in a java directory?

   ls *.java | tail -n 5  
   ls *.java | head -n 5
 
   ls -l *.java | tail -n 5  
   ls -l *.java | head -n 5

5. ls -la *.class | tail -n 12 | wc -l  it will return 12

6.  ls -la *.class | tail -n 12
it will shows last 12 class files list

7.  ls -la *.class | head -n 12 
it will shows first 12 class files list.  

8.      head -c 10 downcasting.java
9.      tail -c 10 downcasting.java
10.   head -c 400  downcasting.java | tail -n 3

(updates still come)

1 comment :

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