First example. Here we compute the length of 3 separate strings. We have a string literal, a String built with from, and a string concatenation.
Info To get the byte count of a string, use the len() function. Each ASCII char counts as one byte.
fn main() {
// Get length of string literal.
let value = "test";
println!("Length = {}", value.len());
// Get length of string.
let value2 = String::from("x");
println!("Length = {}", value2.len());
// Get length of mutable string built from concat.
let mut value3 = String::from("x");
value3 += "y";
println!("Length = {}", value3.len());
}Length = 4
Length = 1
Length = 2
Empty strings. Some strings may have length of 0—these are empty strings. The is_empty function returns true if called on zero length strings.
fn main() {
// This string is not empty.
let value = "?";
if value.is_empty() {
// Not reached.
println!("...")
}
// This string is empty (it has length of 0).
let value2 = "";
if value2.is_empty() {
println!("IS EMPTY")
}
}IS EMPTY
Substring length. It is possible to get a slice (substring) from an existing string, and then get its length. We use the len() function here.
fn main() {
let value = "xyza";
// Get substring and print length.
let result1 = &value[1..3];
println!("Substring = {}", result1);
println!("Length = {}", result1.len());
// Get string from slice and print length.
let result2 = String::from(result1);
println!("Length = {}", result2.len());
}Substring = yz
Length = 2
Length = 2
Summary. We use the len() function to get the byte count of a string in Rust. This tells us the number of bytes, which is the same as the string length for ASCII strings.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
This page was last updated on Oct 24, 2021 (image).
