BZ#10153: Document putenv and setenv return values

[Andreas Jaeger]

The return values of putenv and setenv where not mentioned at all,
fixed with the appended patch.

Ok to commit?

Andreas

2012-04-08  Andreas Jaeger  <aj@suse.de>

	[BZ #10153]
	* manual/startup.texi (Environment Access): Describe return value
	for putenv and setenv.

diff --git a/manual/startup.texi b/manual/startup.texi
index 93dca30..4cd99e5 100644
--- a/manual/startup.texi
+++ b/manual/startup.texi
@@ -335,6 +335,9 @@ definition is added to the environment.  Otherwise, the @var{string} is
 interpreted as the name of an environment variable, and any definition
 for this variable in the environment is removed.
 
+If the function is successful it returns @code{0}.  Otherwise the return
+value is nonzero and @code{errno} is set to indicate the error.
+
 The difference to the @code{setenv} function is that the exact string
 given as the parameter @var{string} is put into the environment.  If the
 user should change the string after the @code{putenv} call this will
@@ -364,6 +367,9 @@ the old entry is replaced by the new one.
 
 Please note that you cannot remove an entry completely using this function.
 
+If the function is successful it returns @code{0}.  Otherwise the return
+value is @code{-1} and @code{errno} is set.
+
 This function was originally part of the BSD library but is now part of
 the Unix standard.
 @end deftypefun

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