Adding realpath function.

* configure: New test for realpath.

* sysif.c (realpath_wrap): New static function.
(sysif_init): Registered realpath intrinsic.

* txr.1: Documented.

3 files changed, 60 insertions, 0 deletions

diff --git a/configure b/configure
index 8c1b5c67..3eb16e7d 100755
--- a/configure
+++ b/configure
@@ -2863,6 +2863,24 @@ else
   printf "no\n"
 fi
 
+printf "Checking for realpath ... "
+cat > conftest.c <<!
+#include <stdlib.h>
+
+int main(void)
+{
+  char *rp = realpath("/var/lib", 0);
+  return 0;
+}
+!
+
+if conftest ; then
+  printf "yes\n"
+  printf "#define HAVE_REALPATH 1\n" >> config.h
+else
+  printf "no\n"
+fi
+
 #
 # Dependent variables
 #
diff --git a/sysif.c b/sysif.c
index 3e14ba97..3e41514b 100644
--- a/sysif.c
+++ b/sysif.c
@@ -1572,6 +1572,19 @@ static val dlvsym_checked(val dlptr, val name, val ver)
 
 #endif
 
+#if HAVE_REALPATH
+static val realpath_wrap(val path)
+{
+  const wchar_t *path_ws = c_str(path);
+  char *path_u8 = utf8_dup_to(path_ws);
+  char *rp_u8 = realpath(path_u8, 0);
+  val rp = if2(rp_u8, string_utf8(rp_u8));
+  free(rp_u8);
+  free(path_u8);
+  return rp;
+}
+#endif
+
 void sysif_init(void)
 {
   prot1(&at_exit_list);
@@ -1943,4 +1956,8 @@ void sysif_init(void)
   reg_varl(intern(lit("rtld-deepbind"), user_package), num_fast(RTLD_DEEPBIND));
 #endif
 #endif
+
+#if HAVE_REALPATH
+  reg_fun(intern(lit("realpath"), user_package), func_n1(realpath_wrap));
+#endif
 }
diff --git a/txr.1 b/txr.1
index ae73c821..1e19a9f9 100644
--- a/txr.1
+++ b/txr.1
@@ -47135,6 +47135,31 @@ function reads the contents of that symbolic link and returns it
 as a string.  Otherwise, it fails by throwing an exception of type
 .codn file-error .
 
+.coNP Function @ realpath
+.synb
+.mets (realpath << path )
+.syne
+.desc
+The
+.code realpath
+function provides access to the same-named POSIX function.
+It processes the input string
+.meta path
+by expanding all symbolic links, removes all superfluous
+.str ".."
+and
+.str "."
+path components, and extra path-separating slash characters,
+to produce a canonical absolute path name.
+
+If the underlying POSIX function indicates failure, then
+.code nil
+is returned. In that situation the
+.code errno
+value is available using the
+.code errno
+function.
+
 .SS* Unix Filesystem Object Existence, Type and Access Tests
 
 The following functions all accept, as the