SAP program RSBDCOS0 can be used to execute external operating system command, such as Unix/Linux Shell commands, from within SAP GUI.
For example, commands like change directory (cd), copy (cp), move (mv) can be executed from withing SAP GUI, to copy or move files on the SAP application server
T-codes CG3Y and CG3Z can also be used in to download files from SAP application server to desktop environment or to upload from desktop to SAP application server. However, these transactions may not work with upload of large files.