Improve description of --label

Fixes bug 22681.

* doc/grep.1 (--label): Use -H in the example, improve wording.
* doc/grep.texi (Output Line Prefix Control): Likewise.

2 files changed, 6 insertions, 6 deletions

diff --git a/doc/grep.1 b/doc/grep.1
index 950b82c5..c0ea754b 100644
--- a/doc/grep.1
+++ b/doc/grep.1
@@ -314,10 +314,10 @@ This is the default when there is only one file
 .BI \-\^\-label= LABEL
 Display input actually coming from standard input as input coming from file
 .I LABEL.
-This is especially useful for tools like
+This is especially useful when implementing tools like
 .BR zgrep ,
 e.g.,
-.B "gzip -cd foo.gz | grep --label=foo something"
+.B "gzip -cd foo.gz | grep --label=foo -H something"
 .TP
 .BR \-n ", " \-\^\-line\-number
 Prefix each line of output with the 1-based line number
diff --git a/doc/grep.texi b/doc/grep.texi
index 2714c58e..a4a87f6a 100644
--- a/doc/grep.texi
+++ b/doc/grep.texi
@@ -414,12 +414,12 @@ This is the default when there is only one file
 @opindex --label
 @cindex changing name of standard input
 Display input actually coming from standard input
-as input coming from file @var{LABEL}.
-This is especially useful for tools like @command{zgrep};
-e.g.:
+as input coming from file @var{LABEL}.  This is
+especially useful when implementing tools like
+@command{zgrep}; e.g.:
 
 @example
-gzip -cd foo.gz | grep --label=foo something
+gzip -cd foo.gz | grep --label=foo -H something
 @end example
 
 @item -n