On the other end, you may be confident that stacks of pushdef 'ed definitions are handled correctly, so are undefine 'd or renamed builtins, changed strings for quotes or comments. When an m4 run is to be frozen, the automatic undiversion which takes place at end of execution is inhibited. Instead, all positively numbered diversions are saved into the frozen file. The active diversion number is also transmitted. A frozen file to be reloaded need not reside in the current directory.
Frozen files are sharable across architectures.
It is safe to write a frozen file one one machine and read it on another, given that the second machine uses the same, or a newer version of GNU m4 . Numbers are always expressed in decimal. V number NL Confirms the format of the file. D number , length NL string NL Selects diversion number , making it current, then copy string in the current diversion. To merely specify an active selection, use this command with an empty string .