The ls command can be used for directories only. Use stat for files.
https://winscp.net/eng/docs/scriptcommand_stat

Hi,
Thanks for the previous answers. They were very useful. Now I'm having the following problem: I like to check the existence of a file in a remote server. For that purpose I'm connecting to it. Then I'm typing "ls name_of_file" and I'm getting the following response:
Error listing directory "name_of_file". and the next line:
CWD failed. "/name_of_file": directory not found.
There is no subdirectories on the place where the file is located - actually there are but I don't have permissions to see them and when I type:
pwd on the server I'm getting response:
/
Thanks in advance.