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-rw-r--r--doc/coreutils.texi19
1 files changed, 13 insertions, 6 deletions
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index ebe379eb6..d6e98c6d6 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -5701,8 +5701,8 @@ Do not check that both input files are in sorted order. This is the default.
@item -e @var{string}
@opindex -e
-Replace those output fields that are missing in the input with
-@var{string}.
+Replace those output fields that are missing in the input with @var{string}.
+I.E. missing fields specified with the @option{-12jo} options.
@item --header
@opindex --header
@@ -5733,10 +5733,17 @@ Join on field @var{field} (a positive integer) of file 2.
Equivalent to @option{-1 @var{field} -2 @var{field}}.
@item -o @var{field-list}
-Construct each output line according to the format in @var{field-list}.
-Each element in @var{field-list} is either the single character @samp{0} or
-has the form @var{m.n} where the file number, @var{m}, is @samp{1} or
-@samp{2} and @var{n} is a positive field number.
+@itemx -o auto
+If the keyword @samp{auto} is specified, infer the output format from
+the first line in each file. This is the same as the default output format
+but also ensures the same number of fields are output for each line.
+Missing fields are replaced with the @option{-e} option and extra fields
+are discarded.
+
+Otherwise, construct each output line according to the format in
+@var{field-list}. Each element in @var{field-list} is either the single
+character @samp{0} or has the form @var{m.n} where the file number, @var{m},
+is @samp{1} or @samp{2} and @var{n} is a positive field number.
A field specification of @samp{0} denotes the join field.
In most cases, the functionality of the @samp{0} field spec