zopencommunity · sachintu47 · Feb 4, 2026 · Feb 4, 2026 · Feb 5, 2026 · Feb 5, 2026
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -55,6 +55,10 @@ if(ZOSLIB_QUICK_STARTUP)
        ZOSLIB_QUICK_STARTUP)
 endif()
 
+# Dataset I/O is always compiled in, controlled by ZOSLIB_DATASET_SUPPORT env var at runtime
+list(APPEND zoslib_defines
+     ZOSLIB_ENABLE_DATASETIO=1)
+
 if(DEFINED ENV{BUILD_VERSION})
   list(APPEND zoslib_defines BUILD_VERSION="$ENV{BUILD_VERSION}")
 endif()

diff --git a/build.sh b/build.sh
@@ -13,6 +13,7 @@ $0
 Builds zoslib, uses xlclang/xlclang++ by default, unless CC is set.
 Options:
 -c    Clean build
+-d    Enable dataset I/O support (default is Disabled)
 -h    Display this message
 -r    Release build (default is Debug)
 -t    Build and run tests
@@ -26,18 +27,22 @@ BLD_TYPE="Debug"
 IS_CLEAN=0
 RUN_TESTS="OFF"
 BLD_TESTS=
+BLD_DSIO=
 
 if test -z "$CC"; then
   export CC=xlclang && export CXX=xlclang++ && export LINK=xlclang++
   IS_CLEAN=1
 fi
 
 nargs=0
-while getopts "chrt" o; do
+while getopts "cdhrt" o; do
   case "${o}" in
     c) IS_CLEAN=1
        ((nargs++))
        ;;
+    d) BLD_DSIO="-DZOSLIB_ENABLE_DATASETIO=ON"
+       ((nargs++))
+       ;;
     r) BLD_TYPE="Release"
        ((nargs++))
        ;;
@@ -65,7 +70,7 @@ pushd build
 export MAKEFLAGS='-j4'
 
 if((IS_CLEAN==1)) || ! test -s CMakeCache.txt; then
-  cmake .. -DCMAKE_C_COMPILER=${CC} -DCMAKE_CXX_COMPILER=${CXX} -DCMAKE_ASM_COMPILER=${CC} ${BLD_TESTS} -DCMAKE_BUILD_TYPE=${BLD_TYPE} -DCMAKE_INSTALL_PREFIX=${SCRIPT_DIR}/install
+  cmake .. -DCMAKE_C_COMPILER=${CC} -DCMAKE_CXX_COMPILER=${CXX} -DCMAKE_ASM_COMPILER=${CC} ${BLD_TESTS} ${BLD_DSIO} -DCMAKE_BUILD_TYPE=${BLD_TYPE} -DCMAKE_INSTALL_PREFIX=${SCRIPT_DIR}/install
 fi
 cmake --build . --target install
 

diff --git a/include/fcntl.h b/include/fcntl.h
@@ -18,6 +18,7 @@ extern "C" {
 /**
  * Same as C open but tags new files as ASCII (819)
  */
+__Z_EXPORT extern int __open_ds_file(const char *filename, int opts, ...);
 __Z_EXPORT extern int __open_ascii(const char *filename, int opts, ...);
 __Z_EXPORT extern int __creat_ascii(const char *filename, mode_t mode);
 #if defined(__cplusplus)
@@ -38,7 +39,7 @@ __Z_EXPORT extern int __creat_ascii(const char *filename, mode_t mode);
 extern "C" {
 #endif
 
-__Z_EXPORT extern int open(const char *filename, int opts, ...) __asm("__open_ascii");
+__Z_EXPORT extern int open(const char *filename, int opts, ...) __asm("__open_ds_file");
 __Z_EXPORT extern int creat(const char *filename, mode_t mode) __asm("__creat_ascii");
 
 #if defined(__cplusplus)

diff --git a/include/stdio.h b/include/stdio.h
@@ -21,6 +21,7 @@ extern "C" {
  * Same as C open but tags new files as ASCII (819)
  */
 __Z_EXPORT extern FILE *__fopen_ascii(const char *filename, const char *mode);
+__Z_EXPORT extern FILE *__fopen_ds_file(const char *filename, const char *mode);
 
 #if defined(__cplusplus)
 }
@@ -37,7 +38,7 @@ __Z_EXPORT extern FILE *__fopen_ascii(const char *filename, const char *mode);
 extern "C" {
 #endif
 
-__Z_EXPORT extern FILE *fopen(const char *filename, const char *mode) __asm("__fopen_ascii");
+__Z_EXPORT extern FILE *fopen(const char *filename, const char *mode) __asm("__fopen_ds_file");
 __Z_EXPORT ssize_t getline(char **lineptr, size_t *n, FILE *stream);
 __Z_EXPORT ssize_t getdelim(char **lineptr, size_t *n, int delimiter, FILE *stream);
 __Z_EXPORT int vasprintf(char **strp, const char *fmt, va_list ap);

diff --git a/include/stdlib.h b/include/stdlib.h
@@ -22,6 +22,7 @@ extern "C" {
 __Z_EXPORT char *__realpath_extended(const char * __restrict__, char * __restrict__);
 #ifdef __NATIVE_ASCII_F
 __Z_EXPORT int __mkstemp_ascii(char*);
+__Z_EXPORT int __mkstemp_ds_file(char*);
 #endif
 #if defined(__cplusplus)
 }
@@ -82,7 +83,7 @@ __Z_EXPORT void free(void* ptr) __THROW __asm("__zoslib_free") ;
  * Same as C mkstemp but tags fd as ASCII (819)
  */
 #undef mkstemp
-__Z_EXPORT int mkstemp(char*) __asm("__mkstemp_ascii");
+__Z_EXPORT int mkstemp(char*) __asm("__mkstemp_ds_file");
 #endif /* __NATIVE_ASCII_F */
 
 #if defined(__cplusplus)

diff --git a/include/sys/stat.h b/include/sys/stat.h
@@ -20,6 +20,8 @@ extern "C" {
  * Same as C mkfifo but tags FIFO special files as ASCII (819)
  */
 __Z_EXPORT extern int __mkfifo_ascii(const char *pathname, mode_t mode);
+__Z_EXPORT extern int __stat_ds_file(const char *path, struct stat *buf);
+__Z_EXPORT extern int __fstat_ds_file(int fd, struct stat *buf);
 
 #if defined(__cplusplus)
 }
@@ -29,14 +31,22 @@ __Z_EXPORT extern int __mkfifo_ascii(const char *pathname, mode_t mode);
 
 #undef mkfifo
 #define mkfifo __mkfifo_replaced
+#undef stat
+#define stat(x,y) __stat_replaced(x,y)
+#undef fstat
+#define fstat(x,y) __fstat_replaced(x,y)
 #include_next <sys/stat.h>
 #undef mkfifo 
+#undef stat
+#undef fstat
 
 #if defined(__cplusplus)
 extern "C" {
 #endif
 
 __Z_EXPORT extern int mkfifo(const char *pathname, mode_t mode) __asm("__mkfifo_ascii");
+__Z_EXPORT extern int stat(const char *path, struct stat *buf) __asm("__stat_ds_file");
+__Z_EXPORT extern int fstat(int fd, struct stat *buf) __asm("__fstat_ds_file");
 
 #if defined(__cplusplus)
 }

diff --git a/include/unistd.h b/include/unistd.h
@@ -10,13 +10,17 @@
 #define ZOS_UNISTD_H_
 
 #include "zos-macros.h"
+#include <sys/types.h>
 
 #if defined(__cplusplus)
 extern "C" {
 #endif
 __Z_EXPORT int __pipe_ascii(int [2]);
 __Z_EXPORT int __close(int);
 __Z_EXPORT int __sysconf(int name);
+__Z_EXPORT ssize_t __write_ds_file(int fd, const void *buf, size_t count);
+__Z_EXPORT ssize_t __read_ds_file(int fd, void *buf, size_t count);
+__Z_EXPORT off_t __lseek_ds_file(int fd, off_t offset, int whence);
 
 #if defined(__cplusplus)
 }
@@ -32,11 +36,20 @@ __Z_EXPORT int __sysconf(int name);
 #define sysconf __sysconf_replaced
 #undef readlink
 #define readlink __readlink_replaced
+#undef write
+#define write __write_replaced
+#undef read
+#define read __read_replaced
+#undef lseek
+#define lseek __lseek_replaced
 #include_next <unistd.h>
 #undef pipe
 #undef close
 #undef sysconf
 #undef readlink
+#undef write
+#undef read
+#undef lseek
 
 #if defined(__cplusplus)
 extern "C" {
@@ -46,10 +59,11 @@ extern "C" {
  */
 __Z_EXPORT int pipe(int [2]) __asm("__pipe_ascii");
 __Z_EXPORT int close(int) __asm("__close");
-__Z_EXPORT int close(int) __asm("__close");
 __Z_EXPORT int sysconf(int name) __asm("__sysconf");
 __Z_EXPORT ssize_t readlink(const char *path, char *buf, size_t bufsiz) __asm("__readlink");
-
+__Z_EXPORT ssize_t write(int fd, const void *buf, size_t count) __asm("__write_ds_file");
+__Z_EXPORT ssize_t read(int fd, void *buf, size_t count) __asm("__read_ds_file");
+__Z_EXPORT off_t lseek(int fd, off_t offset, int whence) __asm("__lseek_ds_file");
 
 #if defined(__cplusplus)
 }

diff --git a/include/zos-base.h b/include/zos-base.h
@@ -66,6 +66,7 @@ extern "builtin" void *_gdsa();
 #define MEMORY_USAGE_LOG_FILE_ENVAR_DEFAULT "__MEMORY_USAGE_LOG_FILE"
 #define MEMORY_USAGE_LOG_LEVEL_ENVAR_DEFAULT "__MEMORY_USAGE_LOG_LEVEL"
 #define MEMORY_USAGE_LOG_INC_ENVAR_DEFAULT "__MEMORY_USAGE_LOG_INC"
+#define DATASET_SUPPORT_ENVAR_DEFAULT "ZOSLIB_DATASET_SUPPORT"
 
 typedef enum {
   __NO_TAG_READ_DEFAULT = 0,
@@ -74,6 +75,11 @@ typedef enum {
   __NO_TAG_READ_STRICT = 3
 } notagread_t;
 
+typedef enum {
+  DS_SUPPORT_YES = 0,
+  DS_SUPPORT_NO = 1
+} ds_support_mode_t;
+
 struct timespec;
 
 extern const char *__zoslib_version;
@@ -506,6 +512,10 @@ typedef struct __Z_EXPORT zoslib_config {
    * allocated, in bytes, after which logging occurs.
    */
   const char *MEMORY_USAGE_LOG_INC_ENVAR = MEMORY_USAGE_LOG_INC_ENVAR_DEFAULT;
+  /**
+   * String to indicate the envar to be used to toggle the dataset support mode.
+   */
+  const char *DATASET_SUPPORT_ENVAR = DATASET_SUPPORT_ENVAR_DEFAULT;
 
 } zoslib_config_t;
 
@@ -553,6 +563,15 @@ typedef struct __Z_EXPORT zoslib_config {
    * to display when memory is allocated or freed.
    */
   const char *MEMORY_USAGE_LOG_LEVEL_ENVAR;
+  /**
+   * String to indicate the envar to be used to specify the increase in memory
+   * allocated, in bytes, after which logging occurs.
+   */
+  const char *MEMORY_USAGE_LOG_INC_ENVAR;
+  /**
+   * String to indicate the envar to be used to toggle the dataset support mode.
+   */
+  const char *DATASET_SUPPORT_ENVAR;
 } zoslib_config_t;
 
 /**
@@ -667,6 +686,7 @@ struct zoslibEnvar {
 class __zinit {
   int mode;
   int cvstate;
+  ds_support_mode_t ds_support_mode;
   std::terminate_handler _th;
 
 public:
@@ -678,6 +698,7 @@ class __zinit {
   ~__zinit();
 
   int initialize(const zoslib_config_t &config);
+  ds_support_mode_t get_ds_support_mode(void) const { return ds_support_mode; }
   bool isValidZOSLIBEnvar(std::string envar);
   int setEnvarHelpMap(void);
   void populateLEFunctionPointers(void);