**Use case**

It prints:
```
ClickHouse has been successfully installed.

Start clickhouse-server with:
 sudo clickhouse start
```

But if clickhouse-server is already running, let's print:
```
ClickHouse has been successfully installed.

Restart clickhouse-server with:
 sudo clickhouse restart
```
{
        UInt64 pid = 0;
        if (fs::exists(pid_file))
        {
            try
            {
                ReadBufferFromFile in(pid_file.string());
                if (tryReadIntText(pid, in))
                {
                    fmt::print("{} file exists and contains pid = {}.\n", pid_file.string(), pid);
                }
                else
                {
                    fmt::print("{} file exists but damaged, ignoring.\n", pid_file.string());
                    fs::remove(pid_file);
                }
            }
            catch (const Exception & e)
            {
                if (e.code() != ErrorCodes::FILE_DOESNT_EXIST)
                    throw;
                
            }
        }
        if (!pid)
        {
            auto sh = ShellCommand::execute("pidof clickhouse-server");
            if (tryReadIntText(pid, sh->out))
            {
                fmt::print("Found pid = {} in the list of running processes.\n", pid);