Read a filename extension.
Extract the final extension from a C++ filesystem path.
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <map>
#include <set>
#include <fstream>
#include <sstream>
#include <filesystem>
#include <iomanip>
int main() {
std::filesystem::path path("reports/summary.csv");
std::cout << path.extension().string() << "\n";
}Expected output EXAMPLE
.csv
Details
Save as snippet.cpp. Compile with g++ -std=c++17 -Wall -Wextra snippet.cpp -o snippet, then run ./snippet. Uses the C++ standard library.
This inspects the path string; the file need not exist.
Tested on Ubuntu 24.04.5 LTS · · g++ (Ubuntu 13.3.0-6ubuntu2~24.04.1) 13.3.0 · g++ 4:13.2.0-7ubuntu1
Test inputs, results and environment
The exact published code ran in a dedicated Linux test container with prepared inputs. Unprivileged snippet process, external networking disabled, read-only root filesystem, and a fresh temporary working directory. Fixtures and output records are isolated from the application database. Testing covers this example and its stated checks, not every input, operating system, or runtime version. The Linux container shares its host's kernel; this is not a native Windows test.
- Architecture / host kernel
- x86_64 / 6.18.54.1-microsoft-standard-WSL2
- Snippet identity / locale
- uid=65534, gid=65534 (unprivileged) / C.UTF-8
- Interpreter invocation
g++ -std=c++17 -Wall -Wextra -Werror snippet.cpp -pthread -lm -o snippet && ./snippet- Container image ID
sha256:32dc2d998158b6554c99b73b533f423696a0f3e31e8cbea9db10b5eee9a2fadd- Code SHA-256
20225497a080148ea5976633ba1863a4ede3ae3c395a2d0e22080102b7d13c6f- Dependencies
- g++ 4:13.2.0-7ubuntu1
Test input setup
These are the prepared inputs used by the test harness. See Details above for the prerequisites and how to run this example.
# No input files required.
Observed standard output
.csv
Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.