Pipe Tutorial

Pipes are used to redirect a stream from one program to another program. The output of one command redirect it to the input of another. It allows us to combine multiple commands.

Pipe Syntax

We use | symbol to separate two commands. By using the | operator, the output of the first command is passed/redirected to the second command. Syntax: command1 | command2

• To find the no of files present in a directory.

  Input: ls -1 | wc -l
  

• To combine both file content using cat and sort it

  Suppose we have two files:- namex.txt and country.txt

  #names
  Leonard
  Sheldon
  Raj
  Amy
  Howard
  Bernadette
  Penny
  Leonard
  

  #country Spain England Italy France Brazil Argentina

    
  Now, to combine both file content using cat and sort  it.
    
  

  Input: cat names.txt country.txt | sort > abc.txt Output:
  Amy Argentina Bernadette Brazil England France Howard Italy Leonard Leonard Penny Raj Sheldon Spain ```

• Find unique records from a file

  To use the uniq command first the data must be in a sorted order.

    Input: cat namex.txt | sort | uniq
    Output: 
    Amy
    Bernadette
    Howard
    Leonard
    Penny
    Raj
    Sheldon
  

• How to see only range of lines in a file

    Input: cat fakenames.txt | head -5
    Output: 
    1,Gregory Mueller 
    2,Mark Jacobs 
    3,Amanda Cooper 
    4,Isaac Conrad 
    5,Ashley Berg      
  

    Input: cat fakenames.txt | head -10 | tail -5 
    Output: 
    6,Nicholas Clark 
    7,Jamie Wright 
    8,Kevin Landry 
    9,Stefanie Johnson 
    10,Annette Johnson    
  

• How to use more and less command

  We use these command when there is large amount of output/data to see in the terminal.

  • The more command displays the output/data from the start and then shows page by page afterwards.

    Input: ls -1 | more
  

  • The less command displays the output/data from the start and then shows in a file type.

    Input: ls -1 | less
  

  we can also search by presing the / and the typing the search keyword.

• tee command in Linux

  The tee command reads the standard input and copies it both to stdOutput and to a file. We can see the information going through pipeline.

```
Input: ls | tee files.txt
```

• XARGS command in Linux

  The xargs command converts the standard input into command line arguement.

    Input: ls | xargs echo
    Output: country.txt fakenames.txt files.txt names.txt sorted_names_country.txt
  
    Input: ls | xargs echo "Hello"
    Output: Hello country.txt fakenames.txt files.txt names.txt sorted_names_country.txt
  

  Example: Suppose we have a file named “FileNames.txt”

    #FileNammes
    file1
    file2
    file3
    file4
    file5
  

  Now, suppose we want to take those names from ‘FileNames.txt’ and create a new file for each of those filenames.

    Input: cat FileNames.txt | xargs touch
  

  Here, the output of cat FileNaes.txt is converted into an command line argument using the xargs and passed it to the touch command using the | operator.