CIGAL Reference Manual, Chapter 2 (Commands): OUTPUT
usage: output [ filename firstvec lastvec nextoutvec compressflag ]
OUTPUT transfers vectors from CIGAL to the vector file: filename.VEC. If the specified file does not exist, OUTPUT creates it. If the file does exist, OUTPUT appends the new set of vectors to the end. Each time OUTPUT appends a set of vectors to a file, those vectors are stored as a separate “drawing”. Each drawing can be read back independently using the INPUT(2) command.
By default OUTPUT transfers all current vectors when it writes. Select a subset of vectors by specifying the arguments FIRSTVEC and LASTVEC (defaults: 1 and #NVEC). Using the argument NEXTOUTVEC can change vectors already written to an existing vector file. NEXTOUTVEC specifies where you want to put the output vectors in the vector file.
COMPRESSFLAG allows you to remove duplicate vectors and retrieve the space occupied by deleted vectors. If COMPRESSFLAG is 0 then all vectors will be saved. If COMPRESSFLAG is non-zero duplicates are stripped out. The default is to copy everything.