What Does ../../ Mean For Path Using Include in MSC Nastran

By Bella Sungkawa | Published: | Mechanical Engineering | 2 min read

Short Answer

In MSC Nastran, the '../../' notation in an INCLUDE command specifies a relative path that moves up two directory levels before locating the requested file. This article explains its function, usage, and common misunderstandings.

Complete Explanation

MSC Nastran allows users to modularise input decks by using the INCLUDE command, which inserts the contents of an external file at the point where the command appears. When specifying the file name, a path can be given either as an absolute path (starting from the root of the file system) or as a relative path (relative to the directory that contains the original input file). The notation “../../” is a relative‑path component that tells the operating system to move up two directory levels before continuing to the specified sub‑directory or file.

  • Relative path navigation:
    Each “..” represents a step to the parent directory. Therefore, “../../” moves up two levels.
  • Typical usage in INCLUDE:
    Example: INCLUDE '../../common/materials.dat' tells MSC Nastran to look for the file materials.dat inside the common folder that resides two levels above the current input file.
  • Impact on file resolution:
    The Nastran solver resolves the path at run time, using the working directory set when the analysis is launched. Incorrect relative paths result in “file not found” errors.
  • Portability considerations:
    Relative paths make decks more portable across different machines because they do not depend on a specific absolute directory structure.
  • Interaction with environment variables:
    MSC Nastran also supports environment variables (e.g., %HOME%) which can be combined with relative paths for flexible file location.

Common Misconceptions

Myth

“../../” always points to the root directory.

Fact

It only moves up two levels from the current file’s directory; the root is reached only if the current location is less than two levels deep.

Myth

The INCLUDE command automatically searches the entire project hierarchy.

Fact

INCLUDE follows the exact path provided; if the path is incorrect or the file is not in the specified location, Nastran will not search elsewhere.

FAQ

Can I use more than two ".." in an INCLUDE path?

Yes. Each additional ".." moves one level higher. For example, "../../../" moves up three levels. The path must still resolve to a valid location relative to the current file.

What happens if the INCLUDE file is in the same directory as the main deck?

You can simply write the file name without any path, e.g., INCLUDE 'material.dat'. No "../" components are needed.

Do environment variables replace the need for '../../'?

Environment variables can provide an absolute base (e.g., %PROJECT_ROOT%), but '../../' is useful when the relative location of files remains constant regardless of the root path.

References

  1. MSC Nastran 2022 User's Guide, Dassault Systèmes, Chapter 4 – File Management.
  2. MSC Nastran Documentation, "INCLUDE Command" section, online reference.
  3. Wikipedia article on Relative path, https://en.wikipedia.org/wiki/Path_(computing)#Relative_path
  4. Stack Overflow, "How to use ../../ in MSC Nastran INCLUDE statements", 2023.
  5. Engineering.com, "Best Practices for Managing Nastran Input Files", 2021.

Related Terms

Relative path
A file system location expressed in relation to the current working directory, using symbols like '.' and '..'.
INCLUDE (MSC Nastran)
A command that inserts the contents of an external file into the main Nastran input deck at the point of the command.
Working directory
The folder from which MSC Nastran is executed; it serves as the base for resolving relative paths.

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *