cat: replace nix with rustix

Author: sylvestre

Cargo.lock

@@ -26,7 +26,7 @@ uucore = { workspace = true, features = ["fast-inc", "fs", "pipes", "signals"] }
 fluent = { workspace = true }
 
 [target.'cfg(unix)'.dependencies]
-nix = { workspace = true }
+rustix = { workspace = true, features = ["fs"] }
 
 [target.'cfg(windows)'.dependencies]
 winapi-util = { workspace = true }

src/uu/cat/Cargo.toml

@@ -84,10 +84,10 @@ enum CatError {
     /// Wrapper around `io::Error`
     #[error("{}", strip_errno(.0))]
     Io(#[from] io::Error),
-    /// Wrapper around `nix::Error`
+    /// Wrapper around `rustix::io::Errno`
     #[cfg(any(target_os = "linux", target_os = "android"))]
     #[error("{0}")]
-    Nix(#[from] nix::Error),
+    Rustix(#[from] rustix::io::Errno),
     /// Unknown file type; it's not a regular file, socket, etc.
     #[error("{}", translate!("cat-error-unknown-filetype", "ft_debug" => .ft_debug))]
     UnknownFiletype {

src/uu/cat/src/cat.rs

@@ -5,8 +5,7 @@
 
 // spell-checker:ignore lseek seekable
 
-use nix::fcntl::{FcntlArg, OFlag, fcntl};
-use nix::unistd::{Whence, lseek};
+use rustix::fs::{OFlags, SeekFrom, fcntl_getfl};
 use std::os::fd::AsFd;
 use uucore::fs::FileInformation;
 
@@ -31,10 +30,10 @@ pub fn is_unsafe_overwrite<I: AsFd, O: AsFd>(input: &I, output: &O) -> bool {
     if file_size == 0 {
         return false;
     }
-    // `lseek` returns an error if the file descriptor is closed or it refers to
+    // `seek` returns an error if the file descriptor is closed or it refers to
     // a non-seekable resource (e.g., pipe, socket, or some devices).
-    let input_pos = lseek(input.as_fd(), 0, Whence::SeekCur);
-    let output_pos = lseek(output.as_fd(), 0, Whence::SeekCur);
+    let input_pos = rustix::fs::seek(input, SeekFrom::Current(0)).map(|v| v as i64);
+    let output_pos = rustix::fs::seek(output, SeekFrom::Current(0)).map(|v| v as i64);
     if is_appending(output) {
         if let Ok(pos) = input_pos {
             if pos >= 0 && (pos as u64) >= file_size {
@@ -54,9 +53,8 @@ pub fn is_unsafe_overwrite<I: AsFd, O: AsFd>(input: &I, output: &O) -> bool {
 
 /// Whether the file is opened with the `O_APPEND` flag
 fn is_appending<F: AsFd>(file: &F) -> bool {
-    let flags_raw = fcntl(file.as_fd(), FcntlArg::F_GETFL).unwrap_or_default();
-    let flags = OFlag::from_bits_truncate(flags_raw);
-    flags.contains(OFlag::O_APPEND)
+    let flags = fcntl_getfl(file).unwrap_or(OFlags::empty());
+    flags.contains(OFlags::APPEND)
 }
 
 #[cfg(test)]

src/uu/cat/src/platform/unix.rs

@@ -4,7 +4,7 @@
 // file that was distributed with this source code.
 use super::{CatResult, FdReadable, InputHandle};
 
-use nix::unistd;
+use rustix::io::{read, write};
 use std::os::{fd::AsFd, unix::io::AsRawFd};
 
 use uucore::pipes::{pipe, splice, splice_exact};
@@ -52,20 +52,20 @@ pub(super) fn write_fast_using_splice<R: FdReadable, S: AsRawFd + AsFd>(
 /// Move exactly `num_bytes` bytes from `read_fd` to `write_fd`.
 ///
 /// Panics if not enough bytes can be read.
-fn copy_exact(read_fd: &impl AsFd, write_fd: &impl AsFd, num_bytes: usize) -> nix::Result<()> {
+fn copy_exact(read_fd: &impl AsFd, write_fd: &impl AsFd, num_bytes: usize) -> std::io::Result<()> {
     let mut left = num_bytes;
     let mut buf = [0; BUF_SIZE];
     while left > 0 {
-        let read = unistd::read(read_fd, &mut buf)?;
-        assert_ne!(read, 0, "unexpected end of pipe");
+        let n = read(read_fd, &mut buf)?;
+        assert_ne!(n, 0, "unexpected end of pipe");
         let mut written = 0;
-        while written < read {
-            match unistd::write(write_fd, &buf[written..read])? {
-                0 => panic!(),
-                n => written += n,
+        while written < n {
+            match write(write_fd, &buf[written..n])? {
+                0 => unreachable!("fd should be writable"),
+                w => written += w,
             }
         }
-        left -= read;
+        left -= n;
     }
     Ok(())
 }