Hi George, > What is the function of gcc/g++ -M option? I have read > through the man page but still can not understand. > Could anyone show me an example please? The -M option is used to create a dependency directed acyclic graph. It is in Makefile depedency format output of file prerequisites. To see how that is used in conjunction with Makefiles, look here: http://www.gnu.org/software/make/manual/html_node/Automatic-Prerequisites.ht ml If you don't use Makefiles, for example if you are using Xcode projects, or if you use certain alternative make systems such as AT&T Nmake, or you ascertain dependencies using a truss-like mechanism, then you needn't bother with -M. HTH, --Eljay
