tzdb::local_tz() function get None ,existing problems tzdb 0.4.1 version

[baoyachi]

ref #101

• rust code

fn main() {

    const PREFIX: &str = "/usr/share/zoneinfo/";

    let mut s = std::fs::read_link("/etc/localtime").unwrap()
        .into_os_string()
        .into_string().unwrap();
 
   println!("{:?}",s);
}

• exec cargo run

~ cargo run
"../usr/share/zoneinfo/Asia/Shanghai"
~

• Then ,see etc/localtime path

~ ls -als /etc/localtime
0 lrwxrwxrwx 1 root root 35 Jul  1 00:46 /etc/localtime -> ../usr/share/zoneinfo/Asia/Shanghai
~

So，above code return Relative path，not a Absolute path. It's seems a bug：https://github.com/strawlab/iana-time-zone/blob/main/src/tz_linux.rs#L18-L29

In iana-time-zone respsitory not include Relative path, May be need fix.

...
    const PREFIX: &str = "/usr/share/zoneinfo/";

    let mut s = read_link("/etc/localtime")?
        .into_os_string()
        .into_string()
        .map_err(|_| crate::GetTimezoneError::FailedParsingString)?;
    if !s.starts_with(PREFIX) {
        return Err(crate::GetTimezoneError::FailedParsingString);
    }

    // Trim to the correct length without allocating.
    s.replace_range(..PREFIX.len(), "");
...

recommend link:https://stackoverflow.com/questions/30511331/getting-the-absolute-path-from-a-pathbuf

[Kijewski]

Please verify if

     let mut s = read_link("/etc/localtime")?
+        .canonicalize()?
         .into_os_string()

would fix the problem for you.

[baoyachi]

Please verify if

     let mut s = read_link("/etc/localtime")?
+        .canonicalize()?
         .into_os_string()

would fix the problem for you.

Not work:

fn main() {

    const PREFIX: &str = "/usr/share/zoneinfo/";

    let mut s = std::fs::read_link("/etc/localtime").unwrap()
+        .canonicalize().unwrap()
        .into_os_string()
        .into_string().unwrap();
    println!("{:?}",s);
}

~ cargo run
+ thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 2, kind: NotFound, message: "No such file or directory" }', src/main.rs:6:25
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
~ 

[Kijewski]

Yes, I noticed the problem: The link has to be relative to /etc not the working directory.

[baoyachi]

Yes, I noticed the problem: The link has to be relative to /etc not the working directory.

You are right