Documentation: describe %ifenv and friends

Signed-off-by: Bryant Keller <bkeller@assembly.ath.cx>
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>

diff --git a/doc/changes.src b/doc/changes.src
index 5e7bf06..e64aae7 100644 (file)
--- a/doc/changes.src
+++ b/doc/changes.src
@@ -9,6 +9,8 @@ since 2007.
 
 \S{cl-2.09} Version 2.09
 
+\b \c{%ifenv}, \c{%elifenv}, \c{%ifnenv}, and \c{%elifnenv} directives introduced.
+
 \b Fixed NULL dereference if environment variable is missed.
 
 \b Updates of new AVX v7 Intel instruciotns.

diff --git a/doc/nasmdoc.src b/doc/nasmdoc.src
index e5d5488..722f099 100644 (file)
--- a/doc/nasmdoc.src
+++ b/doc/nasmdoc.src
@@ -3149,6 +3149,15 @@ any tokens at all, whitespace excepted.
 The usual \i\c{%elifempty}, \i\c\{%ifnempty}, and \i\c{%elifnempty}
 variants are also provided.
 
+\S{ifenv} \i\c{%ifenv}: Test If Environment Variable Exists
+
+The conditional assembly construct \c{%ifenv} assembles the
+subsequent code if and only if the environment variable referenced by
+the \c{%!<env>} directive exists.
+
+The usual \i\c{%elifenv}, \i\c\{%ifnenv}, and \i\c{%elifnenv}
+variants are also provided.
+
 \H{rep} \i{Preprocessor Loops}\I{repeating code}: \i\c{%rep}
 
 NASM's \c{TIMES} prefix, though useful, cannot be used to invoke a