m4: Command line files
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1 2.6 Specifying input files on the command line
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1 The remaining arguments on the command line are taken to be input file
1 names. If no names are present, standard input is read. A file name of
1 '-' is taken to mean standard input. It is conventional, but not
1 required, for input files to end in '.m4'.
1
1 The input files are read in the sequence given. Standard input can
1 be read more than once, so the file name '-' may appear multiple times
1 on the command line; this makes a difference when input is from a
1 terminal or other special file type. It is an error if an input file
1 ends in the middle of argument collection, a comment, or a quoted
1 string.
1
1 The options '--define' ('-D'), '--undefine' ('-U'), '--synclines'
1 ('-s'), and '--trace' ('-t') only take effect after processing input
1 from any file names that occur earlier on the command line. For
1 example, assume the file 'foo' contains:
1
1 $ cat foo
1 bar
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1 The text 'bar' can then be redefined over multiple uses of 'foo':
1
1 $ m4 -Dbar=hello foo -Dbar=world foo
1 =>hello
1 =>world
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1 If none of the input files invoked 'm4exit' (⇒M4exit), the
1 exit status of 'm4' will be 0 for success, 1 for general failure (such
1 as problems with reading an input file), and 63 for version mismatch
1 (⇒Using frozen files).
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1 If you need to read a file whose name starts with a '-', you can
1 specify it as './-file', or use '--' to mark the end of options.
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