* configure: Detect the daemon function.

* eval.c: Include <unistd.h> conditionally.
(errno_wrap, daemon_wrap): New functions.
(eval_init): Registered errno_wrap and daemon_wrap as intrinsics
under the names daemon and errno.

* txr.1: Documented errno and daemon in new UNIX PROGRAMMING
section.

4 files changed, 86 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index b4740778..419ff94b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,17 @@
 2013-11-28  Kaz Kylheku  <kaz@kylheku.com>
 
+	* configure: Detect the daemon function.
+
+	* eval.c: Include <unistd.h> conditionally.
+	(errno_wrap, daemon_wrap): New functions.
+	(eval_init): Registered errno_wrap and daemon_wrap as intrinsics
+	under the names daemon and errno.
+
+	* txr.1: Documented errno and daemon in new UNIX PROGRAMMING
+	section.
+
+2013-11-28  Kaz Kylheku  <kaz@kylheku.com>
+
 	* txr.1: Documented open-tail and make-time.
 
 2013-11-28  Kaz Kylheku  <kaz@kylheku.com>
diff --git a/configure b/configure
index fe27ace2..e318ef17 100755
--- a/configure
+++ b/configure
@@ -1281,6 +1281,8 @@ int x = sizeof ((struct tm *) 0)->$try_field;
   fi
 done
 
+printf "done\n"
+
 printf "Checking for POSIX sleep function ... "
 
 cat > conftest.c <<!
@@ -1301,6 +1303,26 @@ else
   have_unistd=y
 fi
 
+printf "Checking for BSD daemon function ... "
+
+cat > conftest.c <<!
+#include <unistd.h>
+
+int main(int argc, char **argv)
+{
+  daemon(0, 0);
+  return 0;
+}
+!
+rm -f conftest
+if ! $make conftest > conftest.err 2>&1 || ! [ -x conftest ] ; then
+  printf "no\n"
+else
+  printf "yes\n"
+  printf "#define HAVE_DAEMON 1\n" >> config.h
+  have_unistd=y
+fi
+
 #
 # Dependent variables
 #
diff --git a/eval.c b/eval.c
index 395e9abe..4886856c 100644
--- a/eval.c
+++ b/eval.c
@@ -33,6 +33,9 @@
 #include <stdarg.h>
 #include <wchar.h>
 #include "config.h"
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
 #include "lib.h"
 #include "gc.h"
 #include "unwind.h"
@@ -2054,6 +2057,20 @@ static val force(val promise)
   return rplacd(promise, funcall(cdr(promise)));
 }
 
+static val errno_wrap(val newval)
+{
+  val oldval = num(errno);
+  if (newval)
+    errno = c_num(newval);
+  return oldval;
+}
+
+static val daemon_wrap(val nochdir, val noclose)
+{
+  int result = daemon(nochdir ? 1 : 0, noclose ? 1 : 0);
+  return result == 0 ? t : nil;
+}
+
 static void reg_fun(val sym, val fun)
 {
   sethash(top_fb, sym, cons(sym, fun));
@@ -2532,6 +2549,9 @@ void eval_init(void)
   reg_fun(intern(lit("time-string-utc"), user_package), func_n2(time_string_utc));
   reg_fun(intern(lit("make-time"), user_package), func_n7(make_time));
 
+  reg_fun(intern(lit("errno"), user_package), func_n1o(errno_wrap, 0));
+  reg_fun(intern(lit("daemon"), user_package), func_n2(daemon_wrap));
+
   reg_fun(intern(lit("source-loc"), user_package), func_n1(source_loc));
   reg_fun(intern(lit("source-loc-str"), user_package), func_n1(source_loc_str));
 
diff --git a/txr.1 b/txr.1
index 5df7c02d..a647cf53 100644
--- a/txr.1
+++ b/txr.1
@@ -10800,6 +10800,38 @@ If the argument is nil, then the time is assumed not to be in DST.
 If <dst-advice> is :auto, then the function tries to determine whether
 DST is in effect in the current time zone for the specified date and time.
 
+.SH UNIX PROGRAMMING
+
+.SS Functions errno and set-errno
+
+.TP
+Syntax:
+
+   (errno [<new-errno>])
+
+.TP
+Description:
+
+These functions retrieves the current value of the C library error variable
+errno.  If the argument <new-errno> is present and is not nil, then it becomes
+the new value of errno. The value returned is the prior value.
+
+.SS Function daemon
+
+.TP
+Syntax:
+
+  (daemon <nochdir-p> <noclose-p>)
+
+.TP
+Description:
+
+This is a wrapper for the Unix function daemon of BSD origin. 
+
+It returns t if successful, nil otherwise, and the errno
+variable is set in that case.
+
+
 .SH WEB PROGRAMMING SUPPORT
 
 .SS Functions url-encode and url-decode