The read trajectory statement allows one to extract single coordinate sets from a trajectory. It also makes it possible to loop through all or selected frames of a trajectory file and to carry out operations on each frame using X-PLOR's shell language. To facilitate shell-language control of the reading of trajectory files, a symbol $STATUS (of type string) is declared by the read trajectory statement. After an initial call to the read trajectory statement to define the input files and their format, the symbol $STATUS is set to ``READ". The subsequent coordinate sets are read via READ DYNAmics next statements. After the last trajectory frame has been read, the symbol $STATUS is set to ``COMPLETE".