printf

In Unix-like systems, printf is a POSIX-standard command for producing formatted output in the terminal. Unlike echo, which is usually a shell builtin, printf is an external executable that you invoke each time – trading a slight performance cost for precise control over formatting, field widths, alignment, and escape sequences.

echo vs printf

When you run echo, the shell handles it internally:

$ echo "Hello, world!"
Hello, world!

By contrast, printf is an external program:

$ printf "Hello, printf!\n"
Hello, printf!

Format Specifiers

printf uses format specifiers similar to C's printf(). Here are the most common ones:

Example: Strings and Numbers

#!/usr/bin/env bash
course="Advanced Shell Scripting"
printf "Welcome to the %s\n" "$course"

name="Alice"
age=28
weight=65.2
printf "Name: %s | Age: %d | Weight: %.1f kg\n" \
    "$name" "$age" "$weight"

This prints:

Welcome to the Advanced Shell Scripting
Name: Alice | Age: 28 | Weight: 65.2 kg

Escape Sequences and Portability

Different shells handle echo escape sequences inconsistently. For example:

$ echo "Line1\nLine2"
Line1\nLine2
$ echo -e "Line1\nLine2"
Line1
Line2

To ensure portability, use printf which interprets \n, \t, and other escapes by default:

$ printf "Line 1\nLine 2\n"
Line 1
Line 2

Return Status and Character Count

printf returns an exit status (0 on success) and you can pipe its output to wc -c to count characters:

#!/usr/bin/env bash
message="Hello, world!"
if printf "%s" "$message"; then
    count=$(printf "%s" "$message" | wc -c)
    echo -e "\nPrinted $count characters successfully."
else
    echo "Error: printf failed with code $?"
fi

References

• POSIX printf documentation
• GNU Coreutils printf manual
• Bash Shell Builtins