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.

1 files changed, 24 insertions, 0 deletions

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