A simple sudo for launchd scripts

exec-as.nix

{pkgs, ... }: 
{
  nixpkgs.overlays = [
    (final: prev: {
      exec-as = pkgs.writeCBin "exec-as" ''
          #include <stdio.h>
          #include <stdlib.h>
          #include <unistd.h>
          #include <sys/types.h>
          #include <pwd.h>

          void su(const char* username) {
              struct passwd *pw = getpwnam(username);
              if (pw == NULL) {
                  perror("failed to get user information");
                  exit(-1);
              }
              if (setgid(pw->pw_gid) != 0) {
                  perror("failed to set group");
                  exit(-1);
              }
              if (setuid(pw->pw_uid) != 0) {
                  perror("failed to set user");
                  exit(-1);
              }
          }
          int main(int argc, char *argv[]) {
              if (argc < 4) {
                  fprintf(stderr, "Usage: %s <username> <command-path> <command-name> [arguments...]\n", argv[0]);
                  exit(-1);
              }
              su(argv[1]);

              execv(argv[2], &argv[3]);

              perror("execv failed");
              exit(-1);
          }
       ''; 
    })
  ];
}