File: m4.info,  Node: Debugging options,  Next: Command line files,  Prev: Frozen state,  Up: Invoking m4

2.5 Command line options for debugging
======================================

Finally, there are several options for aiding in debugging ‘m4’ scripts.

‘-d[FLAGS]’
‘--debug[=FLAGS]’
     Set the debug-level according to the flags FLAGS.  The debug-level
     controls the format and amount of information presented by the
     debugging functions.  *Note Debug Levels::, for more details on the
     format and meaning of FLAGS.  If omitted, FLAGS defaults to ‘aeq’.

‘--debugfile[=FILE]’
‘-o FILE’
‘--error-output=FILE’
     Redirect ‘dumpdef’ output, debug messages, and trace output to the
     named FILE.  Warnings, error messages, and ‘errprint’ output are
     still printed to standard error.  If these options are not used, or
     if FILE is unspecified (only possible for ‘--debugfile’), debug
     output goes to standard error; if FILE is the empty string, debug
     output is discarded.  *Note Debug Output::, for more details.  The
     option ‘--debugfile’ may be given more than once, and order is
     significant with respect to file names.  The spellings ‘-o’ and
     ‘--error-output’ are misleading and inconsistent with other GNU
     tools; for now they are silently accepted as synonyms of
     ‘--debugfile’ and only recognized once, but in a future version of
     M4, using them will cause a warning to be issued.

‘-l NUM’
‘--arglength=NUM’
     Restrict the size of the output generated by macro tracing to NUM
     characters per trace line.  If unspecified or zero, output is
     unlimited.  *Note Debug Levels::, for more details.

‘-t NAME’
‘--trace=NAME’
     This enables tracing for the macro NAME, at any point where it is
     defined.  NAME need not be defined when this option is given.  This
     option may be given more than once, and order is significant with
     respect to file names.  *Note Trace::, for more details.