pub fn listen_fds() -> io::Result<impl Iterator<Item = RawFd>> {
    struct Guard;

    impl Drop for Guard {
        fn drop(&mut self) {
            env::remove_var("LISTEN_PID");
            env::remove_var("LISTEN_FDS");
        }
    }

    let _guard = Guard;

    let listen_pid = if let Ok(pid) = env::var("LISTEN_PID") {
        pid
    } else {
        return Ok(0..0);
    }
    .parse::<u32>()
    .map_err(|_| io::Error::new(ErrorKind::InvalidInput, "invalid LISTEN_PID"))?;

    if listen_pid != process::id() {
        return Ok(0..0);
    }

    let listen_fds = if let Ok(fds) = env::var("LISTEN_FDS") {
        fds
    } else {
        return Ok(0..0);
    }
    .parse::<u32>()
    .map_err(|_| io::Error::new(ErrorKind::InvalidInput, "invalid LISTEN_FDS"))?;

    let overflow = || io::Error::new(ErrorKind::InvalidInput, "fd count overflowed");

    const SD_LISTEN_FDS_START: u32 = 3;
    let last = SD_LISTEN_FDS_START
        .checked_add(listen_fds)
        .ok_or_else(overflow)?;

    for fd in SD_LISTEN_FDS_START..last {
        fd_cloexec(fd)?
    }

    let last = RawFd::try_from(last).map_err(|_| overflow())?;
    let listen_fds = SD_LISTEN_FDS_START as RawFd..last;
    Ok(listen_fds)
}
/// Checks for file descriptors passed by the service manager for socket
/// activation.
///
/// The function returns an iterator over file descriptors, starting from
/// `SD_LISTEN_FDS_START`. The number of descriptors is obtained from the
/// `LISTEN_FDS` environment variable.
///
/// Before returning, the file descriptors are set as `O_CLOEXEC`.
///
/// See [`sd_listen_fds(3)`][sd_listen_fds] for details.
///
/// [sd_listen_fds]: https://www.freedesktop.org/software/systemd/man/sd_listen_fds.html
///
/// # Example
///
/// ```no_run
/// let socket = sd_notify::listen_fds().map(|mut fds| fds.next().expect("missing fd"));
/// ```
Checks for file descriptors passed by the service manager for socket
activation.

The function returns an iterator over file descriptors, starting from
`SD_LISTEN_FDS_START`. The number of descriptors is obtained from the
`LISTEN_FDS` environment variable.

Before returning, the file descriptors are set as `O_CLOEXEC`.




Checks for file descriptors passed by the service manager for socket activation . The function returns an iterator over file descriptors starting from ` SD_LISTEN_FDS_START ` . The number of descriptors is obtained from the ` LISTEN_FDS ` environment variable . Before returning the file descriptors are set as ` O_CLOEXEC ` .
pub fn listen_fds() -> io::Result<impl Iterator<Item = RawFd>> {
    struct Guard;
    impl Drop for Guard {
        fn drop(&mut self) {
            env::remove_var("LISTEN_PID");
            env::remove_var("LISTEN_FDS");
        }
    }
    let _guard = Guard;
    let listen_pid = if let Ok(pid) = env::var("LISTEN_PID") {
        pid
    } else {
        return Ok(0..0);
    }
    .parse::<u32>()
    .map_err(|_| io::Error::new(ErrorKind::InvalidInput, "invalid LISTEN_PID"))?;
    if listen_pid != process::id() {
        return Ok(0..0);
    }
    let listen_fds = if let Ok(fds) = env::var("LISTEN_FDS") {
        fds
    } else {
        return Ok(0..0);
    }
    .parse::<u32>()
    .map_err(|_| io::Error::new(ErrorKind::InvalidInput, "invalid LISTEN_FDS"))?;
    let overflow = || io::Error::new(ErrorKind::InvalidInput, "fd count overflowed");
    const SD_LISTEN_FDS_START: u32 = 3;
    let last = SD_LISTEN_FDS_START
        .checked_add(listen_fds)
        .ok_or_else(overflow)?;
    for fd in SD_LISTEN_FDS_START..last {
        fd_cloexec(fd)?
    }
    let last = RawFd::try_from(last).map_err(|_| overflow())?;
    let listen_fds = SD_LISTEN_FDS_START as RawFd..last;
    Ok(listen_fds)
}
pub fn listen_fds ( ) -> io :: Result < impl Iterator < Item = RawFd > > { struct Guard ; impl Drop for Guard { fn drop ( & mut self ) { env :: remove_var ( " " ) ; env :: remove_var ( " " ) ; } } let _guard = Guard ; let listen_pid = if let Ok ( pid ) = env :: var ( " " ) { pid } else { return Ok ( 0 .. 0 ) ; } . parse :: < u32 > ( ) . map_err ( | _ | io :: Error :: new ( ErrorKind :: InvalidInput , " " ) ) ? ; if listen_pid != process :: id ( ) { return Ok ( 0 .. 0 ) ; } let listen_fds = if let Ok ( fds ) = env :: var ( " " ) { fds } else { return Ok ( 0 .. 0 ) ; } . parse :: < u32 > ( ) . map_err ( | _ | io :: Error :: new ( ErrorKind :: InvalidInput , " " ) ) ? ; let overflow = | | io :: Error :: new ( ErrorKind :: InvalidInput , " " ) ; const SD_LISTEN_FDS_START : u32 = 3 ; let last = SD_LISTEN_FDS_START . checked_add ( listen_fds ) . ok_or_else ( overflow ) ? ; for fd in SD_LISTEN_FDS_START .. last { fd_cloexec ( fd ) ? } let last = RawFd :: try_from ( last ) . map_err ( | _ | overflow ( ) ) ? ; let listen_fds = SD_LISTEN_FDS_START as RawFd .. last ; Ok ( listen_fds ) }
Checks for file descriptors passed by the service manager for socket
activation.
Checks for file descriptors passed by the service manager for socket activation .
example
```no_run
let socket = sd_notify::listen_fds().map(|mut fds| fds.next().expect("missing fd"));
```
` ` ` no_run let socket = sd_notify :: listen_fds () . map ( |mut fds| fds . next () . expect ( " missing fd " )) ; ` ` `