In Linux and Unix, the echo command is used to write text in files or at the standard output (stdout) and to display the values of variables.
Examples of using echo:
$ echo "Hello"
Hello
$ PI=3.14
$ echo $PI
3.14
The -e option in echo enables the interpretation of special text contstants for string manipulation:
- \n -> newline
- \t -> horizontal tab
- \v -> vertical tab
- \r -> carriage return
- \b -> backspace
- \f -> form feed
- \c -> produce no output
- \a -> ding
Using echo to write text:
Text formatting with echo:
Display text on new line: echo -e “\nText here” or echo -n “Text here”
$ echo -e "\nHello World"
$ echo -n "Hello World"
Insert vertical tab in text string: echo -e “\tText here”
$ echo -e "\tHello World"
Backspace one character in the text: echo -e “\bTText here“
$ echo -e "\bHello World" #This will display ello World
$ echo -e "\bHHello World" #This will display Hello World
These options can be combined together: echo -e “\nThis\tis\ta\bt\ttext”
Displaying the variable values with echo:
With: echo $x
$ x=5
$ echo $x
5
It is recommended to use quotes echoing a variable’s value: echo “$x” for preserving the word splitting or the whitespaces. The quotes protect the special characters inside the variables. Read more here.