sys: Use safe wrapper for libc::isatty

Use the `std::io::IsTerminal` trait introduced in Rust 1.70.

Internally it calls `libc::isatty`, see [1, 2]. Note that it switches
the comparison from `== 1` to `!= 0` which shouldn't make a difference
assuming that libc::isatty upholds the promises made in its man page.

The MSRV was set on the workspace to reflect this change.

[1] https://doc.rust-lang.org/src/std/io/stdio.rs.html#1079
[2] https://doc.rust-lang.org/src/std/sys/unix/io.rs.html#79

Signed-off-by: Maximiliano Sandoval <m.sandoval@proxmox.com>

Cargo.toml

@@ -44,6 +44,7 @@ license = "AGPL-3"
 repository = "https://git.proxmox.com/?p=proxmox.git"
 homepage = "https://proxmox.com"
 exclude = [ "debian" ]
+rust-version = "1.70"
 
 [workspace.dependencies]
 # any features enabled here are enabled on all members using 'workspace = true'!

proxmox-sys/src/linux/tty.rs

@@ -1,4 +1,4 @@
-use std::io::{self, Read, Write};
+use std::io::{self, IsTerminal, Read, Write};
 use std::mem::MaybeUninit;
 use std::os::unix::io::{AsRawFd, OwnedFd};
 
@@ -26,19 +26,15 @@ pub fn stdout_terminal_size() -> (usize, usize) {
 }
 
 /// Returns whether the current stdout is a tty.
-/// # Safety
+#[deprecated(note = "Use std::io::stdout().is_terminal()")]
-///
-/// uses unsafe call to libc::isatty
 pub fn stdout_isatty() -> bool {
-    unsafe { libc::isatty(std::io::stdin().as_raw_fd()) == 1 }
+    std::io::stdout().is_terminal()
 }
 
 /// Returns whether the current stdin is a tty.
-/// # Safety
+#[deprecated(note = "Use std::io::stdin().is_terminal()")]
-///
-/// uses unsafe call to libc::isatty
 pub fn stdin_isatty() -> bool {
-    unsafe { libc::isatty(std::io::stdin().as_raw_fd()) == 1 }
+    std::io::stdin().is_terminal()
 }
 
 pub enum TtyOutput {
@@ -75,7 +71,7 @@ impl TtyOutput {
     /// Get an output file descriptor for the current terminal.
     pub fn open() -> io::Result<Option<Self>> {
         let stdout = std::io::stdout();
-        if unsafe { libc::isatty(stdout.as_raw_fd()) } == 1 {
+        if stdout.is_terminal() {
             Ok(Some(TtyOutput::Stdout(stdout)))
         } else {
             match crate::fd::open(
@@ -97,7 +93,7 @@ impl TtyOutput {
 /// first.
 pub fn read_password(query: &str) -> Result<Vec<u8>, Error> {
     let input = std::io::stdin();
-    if unsafe { libc::isatty(input.as_raw_fd()) } != 1 {
+    if !input.is_terminal() {
         let mut out = String::new();
         input.read_line(&mut out)?;
         return Ok(out.into_bytes());