Function nc::read

pub unsafe fn read(
    fd: i32,
    buf_ptr: usize,
    count: size_t
) -> Result<ssize_t, Errno>

Read from a file descriptor.

Example

let path = "/etc/passwd";
let ret = unsafe { nc::openat(nc::AT_FDCWD, path, nc::O_RDONLY, 0) };
assert!(ret.is_ok());
let fd = ret.unwrap();
let mut buf = [0_u8; 4 * 1024];
let ret = unsafe { nc::read(fd, buf.as_mut_ptr() as usize, buf.len()) };
assert!(ret.is_ok());
let n_read = ret.unwrap();
assert!(n_read <= buf.len() as nc::ssize_t);
let ret = unsafe { nc::close(fd) };
assert!(ret.is_ok());

Examples found in repository

examples/file.rs (line 36)

    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        let n_read = unsafe { nc::read(self.fd, buf.as_mut_ptr() as usize, buf.len()) };
        match n_read {
            Ok(n_read) => Ok(n_read as usize),
            Err(_errno) => Err(io::Error::new(io::ErrorKind::Other, "errno")),
        }
    }

examples/read.rs (line 14)

fn main() -> Result<(), nc::Errno> {
    #[cfg(any(target_os = "linux", target_os = "android"))]
    let fd = unsafe { nc::openat(nc::AT_FDCWD, "/etc/passwd", nc::O_RDONLY, 0)? };

    #[cfg(target_os = "freebsd")]
    let fd = unsafe { nc::open("/etc/passwd", nc::O_RDONLY, 0)? };

    let mut buf: [u8; 256] = [0; 256];
    loop {
        let n_read = unsafe { nc::read(fd, buf.as_mut_ptr() as usize, buf.len()) };
        match n_read {
            Ok(n) => {
                if n == 0 {
                    break;
                }
                // FIXME(Shaohua): Read buf with len(n).
                if let Ok(s) = std::str::from_utf8(&buf) {
                    print!("s: {}", s);
                } else {
                    eprintln!("Failed to read buf as UTF-8!");
                    break;
                }
            }
            Err(errno) => {
                eprintln!("Failed to read, got errno: {}", errno);
                break;
            }
        }
    }

    unsafe { nc::close(fd) }
}