Shell is a most important user interface for HPC users in scientific computing. This paper presents a login shell for computing grid, called GShell, which provides an integrated and uniform environment for constructing, running and managing grid applications. Besides conventional functionality of shell, GShell provides grid-level functionality including grid context maintenance, grid application management interfaces, and extended pipe and redirection semantics. Grid contexts avoid repeat information input when a grid application is started. All the grid applications started in GShell are managed in the grid system, and they can be monitored or stopped in a global scope. Extended shell scripts allow constructing new grid applications using existing tools. At present, GShell has been implemented and applied in the CNGrid project, and is proved to be a simple and flexible command-line tool for most scientists to work in the grid.