From fb9f3a3a46a40dff1122c1410291a0eaf3353331 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Thu, 26 Jan 2017 08:52:23 -0800
Subject: awk macro: provide name of current input via fname.

* share/txr/stdlib/awk.tl (sys:awk-state): New slot, file-name.
(sys:awk-state loop): Set file-name from current input name,
or else from the stream name property if the current input
is a stream object.
(sys:awk-mac-let): New awk macro, fname.

* txr.1: Documented fname.
---
 share/txr/stdlib/awk.tl |  5 +++++
 txr.1                   | 24 ++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/share/txr/stdlib/awk.tl b/share/txr/stdlib/awk.tl
index 9732ea24..05567956 100644
--- a/share/txr/stdlib/awk.tl
+++ b/share/txr/stdlib/awk.tl
@@ -35,6 +35,7 @@
   (inputs)
   (output *stdout*)
   (file-num 0)
+  file-name
   (file-rec-num 0)
   (rec-num 0)
   rec orig-rec fields nf
@@ -119,6 +120,9 @@
   (whilet ((in (pop aws.inputs)))
     (block :awk-file
       (inc aws.file-num)
+      (set aws.file-name (if (streamp in)
+                           (stream-get-prop in :name)
+                           in))
       (when beg-file-func
         [beg-file-func aws])
       (let* ((*stdin* (if (streamp in) in (open-file in)))
@@ -268,6 +272,7 @@
                 (nr (qref ,aws-sym rec-num))
                 (fnr (qref ,aws-sym file-rec-num))
                 (arg (qref ,aws-sym file-num))
+                (fname (qref ,aws-sym file-name))
                 (rs (qref ,aws-sym rs))
                 (krs (qref ,aws-sym krs))
                 (fs (qref ,aws-sym fs))
diff --git a/txr.1 b/txr.1
index c9cbe389..f5a2c8c7 100644
--- a/txr.1
+++ b/txr.1
@@ -43122,6 +43122,30 @@ Thereafter, it is incremented whenever
 .code awk
 switches to a new input source.
 
+.coNP Variable @ fname
+.desc
+The awk variable
+.code fname
+provides access to a character string which, if the current input is
+a file stream, is the name of the underlying file. Assigning to this
+variable changes its value, but has no effect on the input stream.
+Whenever a new input source is used by
+.code awk
+it sets this variable either from the file name on which it is opening
+a stream.. When using an existing stream rather than opening a file,
+.code awk
+sets this variable from the
+.code :name
+property of the stream.
+
+Note that the redirection macros
+.code <-
+and
+.code <!
+have no effect on this variable. Within their scope,
+.code fname
+retains its value.
+
 .coNP Variable @ rs
 .desc
 The awk variable
-- 
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