Enable setting file times for any writable files

src/lib.rs

@@ -239,6 +239,23 @@ where
     imp::set_file_times(p.as_ref(), atime, mtime)
 }
 
+/// Set the last access and modification times for a file on the filesystem to "now".
+/// If `follow_symlinks` is true, then this function follows symlinks; otherwise,
+/// it operates on the file itself, even if it is a symlink.
+///
+/// This function will set the `atime` and `mtime` metadata fields for a file
+/// on the local filesystem, returning any error encountered.
+///
+/// This is not just a convenience function; on unix, a special form of the
+/// syscall is required to convince the kernel to update atime/mtime of files
+/// owned by other users.
+pub fn set_file_times_now<P>(p: P, follow_symlink: bool) -> io::Result<()>
+where
+    P: AsRef<Path>,
+{
+    imp::set_file_times_now(p.as_ref(), follow_symlink)
+}
+
 /// Set the last access and modification times for a file handle.
 ///
 /// This function will either or both of  the `atime` and `mtime` metadata
@@ -253,6 +270,20 @@ pub fn set_file_handle_times(
     imp::set_file_handle_times(f, atime, mtime)
 }
 
+/// Set the last access and modification times for a file handle to "now".
+///
+/// This function will either or both of  the `atime` and `mtime` metadata
+/// fields for a file handle , returning any error encountered. If `None` is
+/// specified then the time won't be updated. If `None` is specified for both
+/// options then no action is taken.
+///
+/// This is not just a convenience function; on unix, a special form of the
+/// syscall is required to convinve the kernel to update atime/mtime of files
+/// owned by other users.
+pub fn set_file_handle_times_now(f: &fs::File) -> io::Result<()> {
+    imp::set_file_handle_times_now(f)
+}
+
 /// Set the last access and modification times for a file on the filesystem.
 /// This function does not follow symlink.
 ///
@@ -302,8 +333,8 @@ where
 #[cfg(test)]
 mod tests {
     use super::{
-        set_file_atime, set_file_handle_times, set_file_mtime, set_file_times,
-        set_symlink_file_times, FileTime,
+        set_file_atime, set_file_handle_times, set_file_handle_times_now, set_file_mtime,
+        set_file_times, set_file_times_now, set_symlink_file_times, FileTime,
     };
     use std::fs::{self, File};
     use std::io;
@@ -486,6 +517,62 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    #[cfg(unix)]
+    // TODO: Do Android and MacOS implement this feature of utimensat?
+    #[cfg(not(target_os = "android"))]
+    #[cfg(not(target_os = "macos"))]
+    fn set_root_file_path_times_test() -> io::Result<()> {
+        // Need a root-owned all-writable file while we execute as non-root.
+        // Thankfully, /dev/null is such a file, and is universally present!
+        let path = Path::new("/dev/null");
+
+        let old_metadata = fs::metadata(&path)?;
+        let old_mtime = FileTime::from_last_modification_time(&old_metadata);
+        let old_atime = FileTime::from_last_access_time(&old_metadata);
+        std::thread::sleep(std::time::Duration::from_millis(10));
+        set_file_times_now(&path, true)?;
+        let new_metadata = fs::metadata(&path)?;
+        let new_mtime = FileTime::from_last_modification_time(&new_metadata);
+        let new_atime = FileTime::from_last_access_time(&new_metadata);
+        // It is possible that something else updated the atime/mtime, so this
+        // test has false negatives (i.e. might succeed when it's supposed to
+        // fail). Note that this should not mean that the test is flaky.
+        assert!(old_mtime < new_mtime, "modification should be updated");
+        assert!(old_atime < new_atime, "access should be updated");
+        Ok(())
+    }
+
+    #[test]
+    #[cfg(unix)]
+    // TODO: Do Android and MacOS implement this feature of futimens?
+    #[cfg(not(target_os = "android"))]
+    #[cfg(not(target_os = "macos"))]
+    fn set_root_file_handle_times_test() -> io::Result<()> {
+        // Need a root-owned all-writable file while we execute as non-root.
+        // Thankfully, /dev/null is such a file, and is universally present!
+        let path = Path::new("/dev/null");
+        let file = std::fs::OpenOptions::new()
+            .write(true)
+            .truncate(false)
+            .open(path)?;
+
+        let old_metadata = fs::metadata(&path)?;
+        let old_mtime = FileTime::from_last_modification_time(&old_metadata);
+        let old_atime = FileTime::from_last_access_time(&old_metadata);
+        std::thread::sleep(std::time::Duration::from_millis(10));
+        set_file_handle_times_now(&file)?;
+        let new_metadata = fs::metadata(&path)?;
+        let new_mtime = FileTime::from_last_modification_time(&new_metadata);
+        let new_atime = FileTime::from_last_access_time(&new_metadata);
+        // It is possible that something else updated the atime/mtime, so this
+        // test has false negatives (i.e. might succeed when it's supposed to
+        // fail). Note that this should not mean that the test is flaky.
+        assert!(old_mtime < new_mtime, "modification should be updated");
+        assert!(old_atime < new_atime, "access should be updated");
+        Ok(())
+    }
+
     #[test]
     fn set_dir_times_test() -> io::Result<()> {
         let td = Builder::new().prefix("filetime").tempdir()?;

src/redox.rs

@@ -15,6 +15,15 @@ pub fn set_file_times(p: &Path, atime: FileTime, mtime: FileTime) -> io::Result<
     set_file_times_redox(fd.raw(), atime, mtime)
 }
 
+pub fn set_file_times_now(p: &Path, follow_symlink: bool) -> io::Result<()> {
+    let time = FileTime::now();
+    if follow_symlink {
+        set_file_times(p, time, time)
+    } else {
+        set_symlink_file_times(p, time, time)
+    }
+}
+
 pub fn set_file_mtime(p: &Path, mtime: FileTime) -> io::Result<()> {
     let fd = open_redox(p, 0)?;
     let st = fd.stat()?;
@@ -71,6 +80,11 @@ pub fn set_file_handle_times(
     set_file_times_redox(f.as_raw_fd() as usize, atime1, mtime1)
 }
 
+pub fn set_file_handle_times_now(f: &File) -> io::Result<()> {
+    let time = FileTime::now();
+    set_file_handle_times(f, Some(time), Some(time))
+}
+
 fn open_redox(path: &Path, flags: i32) -> Result<Fd> {
     match path.to_str() {
         Some(string) => Fd::open(string, flags, 0),

src/unix/android.rs

@@ -9,6 +9,16 @@ pub fn set_file_times(p: &Path, atime: FileTime, mtime: FileTime) -> io::Result<
     set_times(p, Some(atime), Some(mtime), false)
 }
 
+pub fn set_file_times_now(p: &Path, follow_symlink: bool) -> io::Result<()> {
+    let time = FileTime::now();
+    // TODO: Do the same trick as on Linux?
+    if follow_symlink {
+        set_file_times(p, time, time)
+    } else {
+        set_symlink_file_times(p, time, time)
+    }
+}
+
 pub fn set_file_mtime(p: &Path, mtime: FileTime) -> io::Result<()> {
     set_times(p, None, Some(mtime), false)
 }
@@ -36,6 +46,11 @@ pub fn set_file_handle_times(
     }
 }
 
+pub fn set_file_handle_times_now(f: &File) -> io::Result<()> {
+    let time = FileTime::now();
+    set_file_handle_times(f, Some(time), Some(time)) // TODO: Do the same trick as on Linux?
+}
+
 pub fn set_symlink_file_times(p: &Path, atime: FileTime, mtime: FileTime) -> io::Result<()> {
     set_times(p, Some(atime), Some(mtime), true)
 }

src/unix/linux.rs

@@ -16,6 +16,39 @@ pub fn set_file_times(p: &Path, atime: FileTime, mtime: FileTime) -> io::Result<
     set_times(p, Some(atime), Some(mtime), false)
 }
 
+pub fn set_file_times_now(p: &Path, follow_symlink: bool) -> io::Result<()> {
+    let flags = if !follow_symlink {
+        libc::AT_SYMLINK_NOFOLLOW
+    } else {
+        0
+    };
+
+    // Same as `set_file_handle_times` below.
+    static INVALID: AtomicBool = AtomicBool::new(false);
+    if !INVALID.load(SeqCst) {
+        let p = CString::new(p.as_os_str().as_bytes())?;
+        let rc = unsafe {
+            libc::utimensat(
+                libc::AT_FDCWD,
+                p.as_ptr(),
+                ptr::null::<libc::timespec>(),
+                flags,
+            )
+        };
+        if rc == 0 {
+            return Ok(());
+        }
+        let err = io::Error::last_os_error();
+        if err.raw_os_error() == Some(libc::ENOSYS) {
+            INVALID.store(true, SeqCst);
+        } else {
+            return Err(err);
+        }
+    }
+
+    super::utimes::set_file_times_now(p, follow_symlink)
+}
+
 pub fn set_file_mtime(p: &Path, mtime: FileTime) -> io::Result<()> {
     set_times(p, None, Some(mtime), false)
 }
@@ -80,6 +113,59 @@ pub fn set_file_handle_times(
     super::utimes::set_file_handle_times(f, atime, mtime)
 }
 
+pub fn set_file_handle_times_now(f: &fs::File) -> io::Result<()> {
+    eprintln!("Begin linux::set_file_handle_times_now");
+    // Same as `set_file_handle_times` above.
+    static INVALID: AtomicBool = AtomicBool::new(false);
+    if !INVALID.load(SeqCst) {
+        // We normally use a syscall because the `utimensat` function is documented
+        // as not accepting a file descriptor in the first argument (even though, on
+        // Linux, the syscall itself can accept a file descriptor there).
+        #[cfg(not(target_env = "musl"))]
+        let rc = unsafe {
+            eprintln!("linux::set_file_handle_times_now calling non-musl thing");
+            libc::syscall(
+                libc::SYS_utimensat,
+                f.as_raw_fd(),
+                ptr::null::<libc::c_char>(),
+                ptr::null::<libc::timespec>(),
+                0,
+            )
+        };
+        // However, on musl, we call the musl libc function instead. This is because
+        // on newer musl versions starting with musl 1.2, `timespec` is always a 64-bit
+        // value even on 32-bit targets. As a result, musl internally converts their
+        // `timespec` values to the correct ABI before invoking the syscall. Since we
+        // use `timespec` from the libc crate, it matches musl's definition and not
+        // the Linux kernel's version (for some platforms) so we must use musl's
+        // `utimensat` function to properly convert the value. musl's `utimensat`
+        // function allows file descriptors in the path argument so this is fine.
+        #[cfg(target_env = "musl")]
+        let rc = unsafe {
+            libc::utimensat(
+                f.as_raw_fd(),
+                ptr::null::<libc::c_char>(),
+                ptr::null::<libc::timespec>(),
+                0,
+            )
+        };
+
+        eprintln!("linux::set_file_handle_times_now inner done");
+        if rc == 0 {
+            return Ok(());
+        }
+        let err = io::Error::last_os_error();
+        if err.raw_os_error() == Some(libc::ENOSYS) {
+            INVALID.store(true, SeqCst);
+        } else {
+            return Err(err);
+        }
+    }
+
+    eprintln!("linux::set_file_handle_times_now FALLING BACK!!!");
+    super::utimes::set_file_handle_times_now(f)
+}
+
 pub fn set_symlink_file_times(p: &Path, atime: FileTime, mtime: FileTime) -> io::Result<()> {
     set_times(p, Some(atime), Some(mtime), true)
 }
@@ -96,7 +182,7 @@ fn set_times(
         0
     };
 
-    // Same as the `if` statement above.
+    // Same as `set_file_handle_times` above.
     static INVALID: AtomicBool = AtomicBool::new(false);
     if !INVALID.load(SeqCst) {
         let p = CString::new(p.as_os_str().as_bytes())?;

src/unix/macos.rs

@@ -14,6 +14,16 @@ pub fn set_file_times(p: &Path, atime: FileTime, mtime: FileTime) -> io::Result<
     set_times(p, Some(atime), Some(mtime), false)
 }
 
+pub fn set_file_times_now(p: &Path, follow_symlink: bool) -> io::Result<()> {
+    let time = FileTime::now();
+    // TODO: Do the same trick as on Linux?
+    if follow_symlink {
+        set_file_times(p, time, time)
+    } else {
+        set_symlink_file_times(p, time, time)
+    }
+}
+
 pub fn set_file_mtime(p: &Path, mtime: FileTime) -> io::Result<()> {
     set_times(p, None, Some(mtime), false)
 }
@@ -42,6 +52,11 @@ pub fn set_file_handle_times(
     super::utimes::set_file_handle_times(f, atime, mtime)
 }
 
+pub fn set_file_handle_times_now(f: &File) -> io::Result<()> {
+    let time = FileTime::now();
+    set_file_handle_times(f, Some(time), Some(time)) // TODO: Do the same trick as on Linux?
+}
+
 pub fn set_symlink_file_times(p: &Path, atime: FileTime, mtime: FileTime) -> io::Result<()> {
     set_times(p, Some(atime), Some(mtime), true)
 }

src/unix/utimensat.rs

@@ -4,11 +4,41 @@ use std::fs::File;
 use std::io;
 use std::os::unix::prelude::*;
 use std::path::Path;
+use std::ptr;
 
 pub fn set_file_times(p: &Path, atime: FileTime, mtime: FileTime) -> io::Result<()> {
     set_times(p, Some(atime), Some(mtime), false)
 }
 
+pub fn set_file_times_now(p: &Path, follow_symlink: bool) -> io::Result<()> {
+    let flags = if !follow_symlink {
+        if cfg!(target_os = "emscripten") {
+            return Err(io::Error::new(
+                io::ErrorKind::Other,
+                "emscripten does not support utimensat for symlinks",
+            ));
+        }
+        libc::AT_SYMLINK_NOFOLLOW
+    } else {
+        0
+    };
+
+    let p = CString::new(p.as_os_str().as_bytes())?;
+    let rc = unsafe {
+        libc::utimensat(
+            libc::AT_FDCWD,
+            p.as_ptr(),
+            ptr::null::<libc::timespec>(),
+            flags,
+        )
+    };
+    if rc == 0 {
+        Ok(())
+    } else {
+        Err(io::Error::last_os_error())
+    }
+}
+
 pub fn set_file_mtime(p: &Path, mtime: FileTime) -> io::Result<()> {
     set_times(p, None, Some(mtime), false)
 }
@@ -31,6 +61,15 @@ pub fn set_file_handle_times(
     }
 }
 
+pub fn set_file_handle_times_now(f: &File) -> io::Result<()> {
+    let rc = unsafe { libc::futimens(f.as_raw_fd(), ptr::null::<libc::timespec>()) };
+    if rc == 0 {
+        Ok(())
+    } else {
+        Err(io::Error::last_os_error())
+    }
+}
+
 pub fn set_symlink_file_times(p: &Path, atime: FileTime, mtime: FileTime) -> io::Result<()> {
     set_times(p, Some(atime), Some(mtime), true)
 }