diff --git a/src/header/sched/mod.rs b/src/header/sched/mod.rs
index bcdd346..6066550 100644
--- a/src/header/sched/mod.rs
+++ b/src/header/sched/mod.rs
@@ -27,43 +27,110 @@ pub const SCHED_RR: c_int = 1;
 pub const SCHED_OTHER: c_int = 2;
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sched_get_priority_max.html>.
-// #[unsafe(no_mangle)]
+#[unsafe(no_mangle)]
 pub extern "C" fn sched_get_priority_max(policy: c_int) -> c_int {
-    todo!()
+    match policy {
+        SCHED_FIFO | SCHED_RR => 99,
+        SCHED_OTHER => 0,
+        _ => {
+            crate::platform::ERRNO.set(crate::header::errno::EINVAL);
+            -1
+        }
+    }
 }
 
-/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sched_get_priority_max.html>.
-// #[unsafe(no_mangle)]
+/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sched_get_priority_min.html>.
+#[unsafe(no_mangle)]
 pub extern "C" fn sched_get_priority_min(policy: c_int) -> c_int {
-    todo!()
+    match policy {
+        SCHED_FIFO | SCHED_RR => 1,
+        SCHED_OTHER => 0,
+        _ => {
+            crate::platform::ERRNO.set(crate::header::errno::EINVAL);
+            -1
+        }
+    }
 }
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sched_getparam.html>.
-// #[unsafe(no_mangle)]
+#[unsafe(no_mangle)]
 pub unsafe extern "C" fn sched_getparam(pid: pid_t, param: *mut sched_param) -> c_int {
-    todo!()
+    if pid != 0 {
+        crate::platform::ERRNO.set(crate::header::errno::ESRCH);
+        return -1;
+    }
+    crate::platform::ERRNO.set(crate::header::errno::ENOSYS);
+    -1
+}
+
+/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sched_getscheduler.html>.
+#[unsafe(no_mangle)]
+pub extern "C" fn sched_getscheduler(pid: pid_t) -> c_int {
+    if pid != 0 {
+        crate::platform::ERRNO.set(crate::header::errno::ESRCH);
+        return -1;
+    }
+    crate::platform::ERRNO.set(crate::header::errno::ENOSYS);
+    -1
 }
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sched_rr_get_interval.html>.
-// #[unsafe(no_mangle)]
-pub extern "C" fn sched_rr_get_interval(pid: pid_t, time: *const timespec) -> c_int {
-    todo!()
+#[unsafe(no_mangle)]
+pub extern "C" fn sched_rr_get_interval(pid: pid_t, tp: *mut timespec) -> c_int {
+    if pid != 0 {
+        crate::platform::ERRNO.set(crate::header::errno::ESRCH);
+        return -1;
+    }
+    if tp.is_null() {
+        crate::platform::ERRNO.set(crate::header::errno::EINVAL);
+        return -1;
+    }
+    unsafe {
+        (*tp).tv_sec = 0;
+        (*tp).tv_nsec = 100_000_000; // 100ms default SCHED_RR quantum
+    }
+    0
 }
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sched_setparam.html>.
-// #[unsafe(no_mangle)]
-pub unsafe extern "C" fn sched_setparam(pid: pid_t, param: *const sched_param) -> c_int {
-    todo!()
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn sched_setparam(pid: pid_t, _param: *const sched_param) -> c_int {
+    if pid != 0 {
+        crate::platform::ERRNO.set(crate::header::errno::ESRCH);
+        return -1;
+    }
+    crate::platform::ERRNO.set(crate::header::errno::ENOSYS);
+    -1
 }
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sched_setscheduler.html>.
-// #[unsafe(no_mangle)]
+#[unsafe(no_mangle)]
 pub extern "C" fn sched_setscheduler(
     pid: pid_t,
     policy: c_int,
     param: *const sched_param,
 ) -> c_int {
-    todo!()
+    if pid != 0 {
+        crate::platform::ERRNO.set(crate::header::errno::ESRCH);
+        return -1;
+    }
+    match policy {
+        SCHED_OTHER => {
+            if !param.is_null() && unsafe { (*param).sched_priority } != 0 {
+                crate::platform::ERRNO.set(crate::header::errno::EINVAL);
+                return -1;
+            }
+            SCHED_OTHER
+        }
+        SCHED_FIFO | SCHED_RR => {
+            crate::platform::ERRNO.set(crate::header::errno::ENOSYS);
+            -1
+        }
+        _ => {
+            crate::platform::ERRNO.set(crate::header::errno::EINVAL);
+            -1
+        }
+    }
 }
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sched_yield.html>.