tail has a special command line option -f (follow) that allows a file to be monitored. Instead of just displaying the last few lines and exiting, tail keeps displaying the latest lines in the specified file, in real-time. This is particularly useful for monitoring log files.
username@neser:rhel:fen3:$RUN$ tail -f log.icoFoam DILUPBiCG: Solving for Ux, Initial residual = 1.89493e-07, Final residual = 1.89493e-07, No Iterations 0 DILUPBiCG: Solving for Uy, Initial residual = 4.14522e-07, Final residual = 4.14522e-07, No Iterations 0 DICPCG: Solving for p, Initial residual = 1.06665e-06, Final residual = 3.39604e-07, No Iterations 1 time step continuity errors : sum local = 5.25344e-09, global = -9.50761e-19, cumulative = 8.05678e-18 DICPCG: Solving for p, Initial residual = 5.36118e-07, Final residual = 5.36118e-07, No Iterations 0 time step continuity errors : sum local = 6.86432e-09, global = 4.62063e-19, cumulative = 8.51884e-18 ExecutionTime = 0.19 s ClockTime = 0 s . . . .