Author: kevans
Date: Sun Aug 12 00:08:14 2018
New Revision: 337666
URL: https://svnweb.freebsd.org/changeset/base/337666

Log:
  getopt_long(3): Document behavior of leading characters in optstring
  
  Leading '+', '-', and ':' in optstring have special meaning. We briefly
  mention that the first two have special meaning in that we say
  POSIXLY_CORRECT turns them off, but we don't actually document their
  meaning. Add a paragraph to RETURN VALUES explaining how they control
  the treatment of non-option arguments.
  
  A leading ':' has no mention; add a note that it suppresses warnings about
  missing arguments.
  
  Reviewed by:  jilles
  MFC after:    1 week
  Differential Revision:        https://reviews.freebsd.org/D14142

Modified:
  head/lib/libc/stdlib/getopt_long.3

Modified: head/lib/libc/stdlib/getopt_long.3
==============================================================================
--- head/lib/libc/stdlib/getopt_long.3  Sun Aug 12 00:06:21 2018        
(r337665)
+++ head/lib/libc/stdlib/getopt_long.3  Sun Aug 12 00:08:14 2018        
(r337666)
@@ -31,7 +31,7 @@
 .\"     @(#)getopt.3   8.5 (Berkeley) 4/27/95
 .\" $FreeBSD$
 .\"
-.Dd December 25, 2011
+.Dd May 2, 2018
 .Dt GETOPT_LONG 3
 .Os
 .Sh NAME
@@ -207,12 +207,53 @@ these functions return 0 and store
 .Fa val
 in the location pointed to by
 .Fa flag .
+.Pp
 These functions return
 .Ql \&:
-if there was a missing option argument,
+if there was a missing option argument and error messages are suppressed,
 .Ql \&?
 if the user specified an unknown or ambiguous option, and
 \-1 when the argument list has been exhausted.
+The default behavior when a missing option argument is encountered is to write
+an error and return
+.Ql \&? .
+Specifying
+.Ql \&:
+in
+.Fa optstr
+will cause the error message to be suppressed and
+.Ql \&:
+to be returned instead.
+.Pp
+In addition to
+.Ql \&: ,
+a leading
+.Ql \&+
+or
+.Ql \&-
+in
+.Fa optstr
+also has special meaning.
+If either of these are specified, they must appear before
+.Ql \&: .
+.Pp
+A leading
+.Ql \&+
+indicates that processing should be halted at the first non-option argument,
+matching the default behavior of
+.Xr getopt 3 .
+The default behavior without
+.Ql \&+
+is to permute non-option argments to the end of
+.Fa argv .
+.Pp
+A leading
+.Ql \&-
+indicates that all non-option arguments should be treated as if they are
+arguments to a literal
+.Ql \&1
+flag (i.e., the function call will return the value 1, rather than the char
+literal '1').
 .Sh ENVIRONMENT
 .Bl -tag -width ".Ev POSIXLY_CORRECT"
 .It Ev POSIXLY_CORRECT
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