LIFELINE, the ULiège program for the simulation of the X-ray LIne proFiles in massivE coLliding wInd biNariEs which is designed to compute the profile of emission lines emitted in X-rays in the colliding wind region of massive stars binaries. It was developed as programmable, interactive tool for studying the physics of the winds in binary systems, the emission of X-ray lines and the comparison with the observations. LIFELINE is written entirely in python and is intended to be portable across most Unix operating systems. LIFELINE requires python v2.7, its pyatomdb package and, optionally, the ATOMDB database. This program was developed by the Enmanuelle Mossoux at the University of Liège (Belgium) under the XMM PRODEX contract (Belspo), from the Fonds de la Recherche Scientifique (FRS/FNRS). This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see . For information about the program, see Manual.pdf.