std: Wrap setpgid on POSIX

lib/std/c.zig

@@ -9167,6 +9167,7 @@ pub extern "c" fn setreuid(ruid: uid_t, euid: uid_t) c_int;
 pub extern "c" fn setregid(rgid: gid_t, egid: gid_t) c_int;
 pub extern "c" fn setresuid(ruid: uid_t, euid: uid_t, suid: uid_t) c_int;
 pub extern "c" fn setresgid(rgid: gid_t, egid: gid_t, sgid: gid_t) c_int;
+pub extern "c" fn setpgid(pid: pid_t, pgid: pid_t) c_int;
 
 pub extern "c" fn malloc(usize) ?*anyopaque;
 pub extern "c" fn realloc(?*anyopaque, usize) ?*anyopaque;

lib/std/os/linux.zig

@@ -1551,6 +1551,10 @@ pub fn setresgid(rgid: gid_t, egid: gid_t, sgid: gid_t) usize {
     }
 }
 
+pub fn setpgid(pid: pid_t, pgid: pid_t) usize {
+    return syscall2(.setpgid, @intCast(pid), @intCast(pgid));
+}
+
 pub fn getgroups(size: usize, list: *gid_t) usize {
     if (@hasField(SYS, "getgroups32")) {
         return syscall2(.getgroups32, size, @intFromPtr(list));

lib/std/posix.zig

@@ -3415,6 +3415,24 @@ pub fn setregid(rgid: gid_t, egid: gid_t) SetIdError!void {
     }
 }
 
+pub const SetPgidError = error{
+    ProcessAlreadyExec,
+    InvalidProcessGroupId,
+    PermissionDenied,
+    ProcessNotFound,
+} || UnexpectedError;
+
+pub fn setpgid(pid: pid_t, pgid: pid_t) SetPgidError!void {
+    switch (errno(system.setpgid(pid, pgid))) {
+        .SUCCESS => return,
+        .ACCES => return error.ProcessAlreadyExec,
+        .INVAL => return error.InvalidProcessGroupId,
+        .PERM => return error.PermissionDenied,
+        .SRCH => return error.ProcessNotFound,
+        else => |err| return unexpectedErrno(err),
+    }
+}
+
 /// Test whether a file descriptor refers to a terminal.
 pub fn isatty(handle: fd_t) bool {
     if (native_os == .windows) {