01. Standard Outputting echo, printf

The echo command is an easy way of outputting data to a user.

$ echo 'Hello world!'
Hello world!
$ echo $PS1

This command is extremely useful, but primitive. Can we do better?

We could use echo with the option -e to use escape sequences.

suppress new line
new line
carriage return
horizontal tab

Can we do even better, making sure our code is 100% portable and POSIX standard? Yes, we can with printf.

Fancy printing with printf

In order to make a more flexible command that complies with POSIX standards, the printf command was adopted.

Although certainly more flexible, the printf command forces the user to be more explicit. For example, the newline character is not defaulted like it is in echo - we must supply it on our own.

$ printf "Hello world!\n"
Hello world!

Format specifiers

Just like printf is used in C and many other compiled languages, we may supply it a variable proceeding the declaration. For example:

$ printf "Hello my name is %s %s.\n" Tony Dylan
Hello my name is Tony Dylan.

The %s is a variable that stands in for strings, while the %d stands in for integers.

$ printf "I am %d years old" 44
I am 44 years old
$ printf "I am %d years old" 0x2c
I am 44 years old

To print floating point values, use the %f specifier.

$ printf "The child is %f years old.\n" 3.5
The child is 3.5 years old.


To limit decimal places, we can place a decimal point and the precision within the floating specifier.

$ printf "%.2f\n" 3

To place spaces before a numerical value, we can do so with just an integer value.

$ printf "I am %4d years old.\n" 13
I am   13 years old.

To pad a number with zeros, precede with a zero.

$ printf "I am %04d years old.\n" 13
I am 0013 years old.

Treating "anomalies"

If there are fewer stand-ins than variables supplied, then the shell repeats the line until done.

$ printf "I ate some %s.\n" eggs chicken bacon
I ate some eggs. 
I ate some chicken. 
I ate some bacon.

On the other hand, if there are more stand-ins than variables, then the shell simply omits them.

$ printf "I ate some %s, %s and %s.\n" eggs chicken
I ate some eggs, chicken and .

Aching back from coding all day?

Prism Glasses

Aching back from coding all day? Try Back Problems

Ever feel achy from sitting crunched up on your computer table? Try lying down with these optical glasses that allow you to work on your laptop while lying flat on your back. This is the perfect solution with those with limited mobility or those who wish to prevent neck cramps and back strains.

$ Check price
4.454.45Amazon 4 logo(128+ reviews)

More Back Problems resources

Take your Linux skills to the next level!

Linux for Beginners

Take your Linux skills to the next level! Try Linux & UNIX

Linux for Beginners doesn't make any assumptions about your background or knowledge of Linux. You need no prior knowledge to benefit from this book. You will be guided step by step using a logical and systematic approach. As new concepts, commands, or jargon are encountered they are explained in plain language, making it easy for anyone to understand.

$ Check price
24.9924.99Amazon 4.5 logo(101+ reviews)

More Linux & UNIX resources