In this small blog we will learn how to create a file with different file extensions and how can we write some text or paragraph in the file? how to write content of one file to another file. We can also use cat command to append the binary data.We can use the following commands to create and write in a file :

1- touch

2- cat

3- echo

4- printf

Let us check a demo for each above command with the help of an example:

Example 1: using “touch” command

Let us create a file having extension “.php” using command “touch”

Below we are creating a php file named demo (i.e. demo.php)

username@machinename:~$ touch demo.php  

This file will be created in our home directory

Here we will use command "cat" to create a file in a given path.

Example 2: using “cat >” command

Let us create a file having extension “.txt” using command “cat >”

username@machinename:~$ cat > demo2.txt   
  This text will be written in the file demo2.txt
  Hello world

for returning to the command prompt we will use combination of keys “Ctrl” + “D”

Let us create a file having extension “.txt” using command “echo > filename”

Example 3: using “echo > filename” command

1)  username@machinename:~$ echo  > demo3.txt   
2)  username@machinename:~$ echo 'First line in the text ' > demo3.txt   
3)  username@machinename:~$ echo 'Second line in the text' > demo3.txt

command in 1) will create a file demo3.txt in home directory.

command in 2) will create a file demo3.txt in home directory, also it will contain the text “First line in the text ”

command in 3) will over write the existing text in the file demo3.txt

Let us create a file having extension “.txt” using command “printf > filename”

Example 4: using “printf > filename” command

1)  username@machinename:~$ printf  > demo4.txt

this command will create the file demo4.txt. But on command line interface we will get a message as: printf: usage: printf [-v var] format [arguments]

to avoid this we can write the command as below:

2) username@machinename:~$ printf '' > demo4.txt

Now if we want to write the content of one file to another file we again use the “cat” command as below:

username@machinename:~$ cat demo3.txt > demo5.txt

The above command will over write all the text in the demo5.txt from demo3.txt

Now to check the content of the file demo5.txt we again use the command “cat”

username@machinename:~$ cat demo5.txt