IOSS: Add select_steps option to io_shell

Author: gsjaardema

packages/seacas/libraries/ioss/src/Ioss_CopyDatabase.C

@@ -371,6 +371,21 @@ namespace {
         }
       }
     }
+    else if (!options.selected_steps.empty()) {
+      for (const auto &step : options.selected_steps) {
+	if (step == 0 || abs(step) > step_count) {
+	  fmt::print(std::cerr, "WARNING: Step {} is out of range. Must be non-zero and maximum of {}.\n",
+		     step, step_count);
+	  continue;
+	}
+	if (step > 0) {
+	  selected_steps[step] = 1;
+	}
+	else {
+	  selected_steps[step_count + 1 + step] = 1;
+	}
+      }
+    }
     else {
       // User did not select specific times to be output...
       // Just select them all

packages/seacas/libraries/ioss/src/Ioss_MeshCopyOptions.h

@@ -1,6 +1,6 @@
 #pragma once
 /*
- * Copyright(C) 1999-2024 National Technology & Engineering Solutions
+ * Copyright(C) 1999-2025 National Technology & Engineering Solutions
  * of Sandia, LLC (NTESS).  Under the terms of Contract DE-NA0003525 with
  * NTESS, the U.S. Government retains certain rights in this software.
  *
@@ -14,6 +14,7 @@ namespace Ioss {
   struct IOSS_EXPORT MeshCopyOptions
   {
     std::vector<double>      selected_times{};
+    std::vector<int>         selected_steps{};
     std::vector<std::string> omitted_sets{};
     std::string              selected_change_sets{};
     double                   minimum_time{0.0};

packages/seacas/libraries/ioss/src/Ioss_Region.C

@@ -630,7 +630,7 @@ namespace Ioss {
         " Element side sets  = {16:{24}}\t Element sides = {22:{23}}\t Sideset    = {31:{25}}\n"
         " Assemblies         = {40:{24}}\t                 {38:{23}s}\t Assembly   = {41:{25}}\t{54:{25}}\n"
         " Blobs              = {42:{24}}\t                 {38:{23}s}\t Blob       = {43:{25}}\t{55:{25}}\n\n"
-        " Time steps         = {32:{24}}\n",
+        " Time steps         = {32:{24}}",
         get_database()->get_filename(), mesh_type_string(),                /* 0, 1 */
         fmt::group_digits(get_property("spatial_dimension").get_int()),
 	fmt::group_digits(get_property("node_count").get_int()),
@@ -687,6 +687,13 @@ namespace Ioss {
 	fmt::group_digits(num_asm_red_vars),
         fmt::group_digits(num_blob_red_vars),
 	change_set_name, change_set_count);
+
+    if (num_ts > 0) {
+      fmt::print("\t({} to {})\n", stateTimes[0], stateTimes[num_ts-1]);
+    }
+    else {
+      fmt::print("\n");
+    }
     // clang-format on
   }
 

packages/seacas/libraries/ioss/src/main/io_shell.C

@@ -59,6 +59,7 @@ namespace {
   {
     Ioss::MeshCopyOptions options{};
     options.selected_times       = interFace.selected_times;
+    options.selected_steps       = interFace.selected_steps;
     options.rel_tolerance        = interFace.rel_tolerance;
     options.abs_tolerance        = interFace.abs_tolerance;
     options.tol_floor            = interFace.tol_floor;

packages/seacas/libraries/ioss/src/main/shell_interface.C

@@ -285,6 +285,11 @@ void IOShell::Interface::enroll_options()
                   "comma-separated list of times that should be transferred to output database",
                   nullptr);
 
+  options_.enroll("select_steps", Ioss::GetLongOption::OptType::MandatoryValue,
+                  "comma-separated list of steps that should be transferred to output database\n"
+		  "\t\tEnter a negative value to count from end. -1 is last, -2 is second last.",
+                  nullptr);
+
   options_.enroll("append_after_time", Ioss::GetLongOption::OptType::MandatoryValue,
                   "add steps on input database after specified time on output database", nullptr);
 
@@ -793,6 +798,24 @@ bool IOShell::Interface::parse_options(int argc, char **argv, int my_processor)
     }
   }
 
+  {
+    const char *temp = options_.retrieve("select_steps");
+    if (temp != nullptr) {
+      if (!selected_times.empty()) {
+        if (my_processor == 0) {
+          fmt::print(stderr, "ERROR: Can not use both select_times and select_steps.\n");
+        }
+        return false;
+      }
+
+      auto step_str = Ioss::tokenize(std::string(temp), ",");
+      for (const auto &str : step_str) {
+        auto step = std::stoi(str);
+        selected_steps.push_back(step);
+      }
+    }
+  }
+
   append_time    = options_.get_option_value("append_after_time", append_time);
   flush_interval = options_.get_option_value("flush_interval", flush_interval);
   timestep_delay = options_.get_option_value("delay", timestep_delay);

packages/seacas/libraries/ioss/src/main/shell_interface.h

@@ -1,5 +1,5 @@
 /*
- * Copyright(C) 1999-2024 National Technology & Engineering Solutions
+ * Copyright(C) 1999-2025 National Technology & Engineering Solutions
  * of Sandia, LLC (NTESS).  Under the terms of Contract DE-NA0003525 with
  * NTESS, the U.S. Government retains certain rights in this software.
  *
@@ -61,6 +61,10 @@ namespace IOShell {
     //! If non-empty, then it is a list of times that should be transferred to the output file.
     std::vector<double> selected_times{};
 
+    //! If non-empty, then it is a list of steps that should be transferred to the output file.
+    //  A negative value counts from end. -1 is last, -2 is second last...
+    std::vector<int> selected_steps{};
+
     //! If non-empty, then it is a list of element blocks, nodesets,
     //! sidesets that should be omitted from the output file
     std::vector<std::string> omitted_blocks{};