tempname — Generate unique temporary paths in the system temp directory or a specified target folder.

tempname generates a unique path string suitable for temporary files or folders. By default it uses the system temporary directory and supports MATLAB-compatible optional base-folder overrides.

Syntax

filename = tempname()
filename = tempname(folder)

Inputs

Returns

Errors

How tempname works

• tempname() returns a character row vector (1×N) containing an absolute path inside the system temporary directory.
• tempname(folder) returns a path inside folder, which can be absolute or relative. RunMat expands leading ~ to the home directory for convenience.
• The returned path never corresponds to an existing file or directory at the time of the call.
• tempname does not create files or directories. Use the returned value with builtins such as fopen, mkdir, or movefile.
• The generated token begins with the MATLAB-compatible tp prefix followed by hexadecimal entropy, making it human-recognisable while avoiding collisions.
• Providing more than one input argument raises tempname: too many input arguments. Non-text inputs raise a descriptive type error.

Does RunMat run tempname on the GPU?

tempname performs all computation on the CPU. When scripts pass GPU-resident strings (for example, gpuArray("scratch")), RunMat automatically gathers those scalars to host memory before determining the result. Acceleration providers do not implement hooks for this builtin, and there is no GPU kernel to warm up.

GPU memory and residency

No. tempname only manipulates paths and never benefits from GPU execution. It always returns a host-resident character array. If you accidentally store a folder name on the GPU, RunMat gathers it transparently.

Examples

Generate A Unique Temporary File Name

fname = tempname();
fprintf("Saving intermediate results to %s\n", fname)

Expected output:

% Prints the unique file name inside the system temporary folder.

Create A Temporary File Name In A Custom Folder

logDir = fullfile(pwd(), "logs");
fname = tempname(logDir)

Expected output:

% fname starts with the logs folder and ends with a tp******** token.

Append A File Extension To Tempname Results

csvPath = [tempname(), ".csv"]

Expected output:

% csvPath is a unique .csv file path you can pass to writematrix or fprintf.

Reserve A Temporary Folder Path

scratch = tempname();
mkdir(scratch);
cleanupObj = onCleanup(@() rmdir(scratch, "s"))

Expected output:

% scratch now exists on disk and is removed automatically via onCleanup.

Use Tempname With fopen To Write Temporary Data

tmpFile = tempname();
[fid, message] = fopen(tmpFile, "w");
if fid == -1
    error("Failed to open temp file: %s", message);
end
fprintf(fid, "Temporary output\n");
fclose(fid)

Expected output:

% Creates a file, writes text, and leaves it for later processing.

Combine Tempname With gpuArray Inputs

folder = gpuArray("scratch");
fname = tempname(folder)

Expected output:

% RunMat gathers the string and returns a host-side character vector.

Using tempname with coding agents

Open a RunMat example with live inputs, then ask the agent to explain how tempname changes the result.

FAQ

Related Io functions

Open-source implementation

Unlike proprietary runtimes, every RunMat function is open-source. Read exactly how tempname is executed, line by line, in Rust.

• View the source for tempname in Rust on GitHub
• Learn how the RunMat runtime works
• Found a bug? Open an issue with a minimal reproduction.

About RunMat

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