Implement tcgetsid using ioctl

src/header/termios/mod.rs

@@ -9,7 +9,7 @@ use crate::{
     },
     platform::{
         self,
-        types::{c_int, c_ulong, c_void},
+        types::{c_int, c_ulong, c_void, pid_t},
     },
 };
 
@@ -85,6 +85,16 @@ pub unsafe extern "C" fn tcsetattr(fd: c_int, act: c_int, value: *const termios)
     sys_ioctl::ioctl(fd, sys_ioctl::TCSETS + act as c_ulong, value as *mut c_void)
 }
 
+/// See <https://pubs.opengroup.org/onlinepubs/009695299/functions/tcgetsid.html>.
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn tcgetsid(fd: c_int) -> pid_t {
+    let mut sid = 0;
+    if sys_ioctl::ioctl(fd, sys_ioctl::TIOCGSID, (&raw mut sid) as *mut c_void) < 0 {
+        return -1;
+    }
+    sid
+}
+
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/cfgetispeed.html>.
 #[cfg(target_os = "linux")]
 #[unsafe(no_mangle)]