File: autoconf.info,  Node: Command Line Prefixes,  Next: Special Chars in Names,  Prev: Failure in Make Rules,  Up: Portable Make

12.3 Makefile Command Line Prefixes
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Makefile command lines can be preceded by zero or more of the command
line prefixes ‘-’, ‘@’, and ‘+’, which modify how ‘make’ processes the
command.  Although POSIX says these are the only command line prefixes,
some ‘make’ implementations, such as Solaris ‘make’, support the
additional prefixes ‘!’ and ‘?’.  Portable makefiles should therefore
avoid using these two characters at the start of a makefile command
line.  For example:

     mishandled-by-Solaris-make:; ! grep FIXME foo.c
     portable-to-Solaris-make:; :;! grep FIXME foo.c