numfmt: implement support for field ranges

* src/numfmt.c: Replace field handling code with logic that understands
field range specifiers.  Instead of processing a single field and
printing line prefix/suffix around it, process each field in the line
checking whether it has been included for conversion.  If so convert and
print, otherwise just print the unaltered field.
(extract_fields): Removed.
(skip_fields): Removed.
(process_line): Gutted and heavily reworked.
(process_suffixed_number): FIELD is now passed as an arg instead of
using a global.
(parse_field_arg): New function that parses field range specifiers.
(next_field): New function that returns pointers to the next field in
a line.
(process_field): New function that wraps the field conversion logic
(include_field): New function that checks whether a field should be
converted
(compare_field): New function used for field value comparisons in a
gl_list.
(free_field): New function used for freeing field values in a gl_list.
Global variable FIELD removed.
New global variable all_fields indicates whether all fields should be
processed.
New global variable all_fields_after stores the first field of a N-
style range.
New global variable all_fields_before stores the last field of a -M
style range.
New global variable field_list stores explicitly specified fields to
process (N N,M or N-M style specifiers).
(usage): Document newly supported field range specifiers.
* bootstrap.conf: Include xlist and linked-list modules.  numfmt now
uses the gl_linked_list implementation to store the field ranges.
* tests/misc/numfmt.pl: Add tests for 'cut style' field ranges.
Adjust existing tests as partial output can occur before an error
Remove test for the 'invalid' field -5.. this is now a valid range.
* gnulib: update to avoid compiler warnings in linked-list.
* NEWS: Mention the new feature.

1 files changed, 12 insertions, 2 deletions

diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 08316c928..9197cb426 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -16892,9 +16892,19 @@ Print (to standard error) warning messages about possible erroneous usage.
 Use the character @var{d} as input field separator (default: whitespace).
 @emph{Note}: Using non-default delimiter turns off automatic padding.
 
-@item --field=@var{n}
+@item --field=@var{fields}
 @opindex --field
-Convert the number in input field @var{n} (default: 1).
+Convert the number in input field @var{fields} (default: 1).
+@var{fields} supports @command{cut} style field ranges:
+
+@example
+N    N'th field, counted from 1
+N-   from N'th field, to end of line
+N-M  from N'th to M'th field (inclusive)
+-M   from first to M'th field (inclusive)
+-    all fields
+@end example
+
 
 @item --format=@var{format}
 @opindex --format