Function std::io::read_to_string
1.65.0 · source · pub fn read_to_string<R: Read>(reader: R) -> Result<String>
Expand description
Read all bytes from a reader into a new String
.
This is a convenience function for Read::read_to_string
. Using this
function avoids having to create a variable first and provides more type
safety since you can only get the buffer out if there were no errors. (If you
use Read::read_to_string
you have to remember to check whether the read
succeeded because otherwise your buffer will be empty or only partially full.)
§Performance
The downside of this function’s increased ease of use and type safety is
that it gives you less control over performance. For example, you can’t
pre-allocate memory like you can using String::with_capacity
and
Read::read_to_string
. Also, you can’t re-use the buffer if an error
occurs while reading.
In many cases, this function’s performance will be adequate and the ease of use
and type safety tradeoffs will be worth it. However, there are cases where you
need more control over performance, and in those cases you should definitely use
Read::read_to_string
directly.
Note that in some special cases, such as when reading files, this function will
pre-allocate memory based on the size of the input it is reading. In those
cases, the performance should be as good as if you had used
Read::read_to_string
with a manually pre-allocated buffer.
§Errors
This function forces you to handle errors because the output (the String
)
is wrapped in a Result
. See Read::read_to_string
for the errors
that can occur. If any error occurs, you will get an Err
, so you
don’t have to worry about your buffer being empty or partially full.
§Examples
fn main() -> io::Result<()> {
let stdin = io::read_to_string(io::stdin())?;
println!("Stdin was:");
println!("{stdin}");
Ok(())
}
Run