mirror of
https://github.com/yhirose/cpp-httplib.git
synced 2026-04-12 19:58:29 +00:00
51 lines
1.8 KiB
Markdown
51 lines
1.8 KiB
Markdown
---
|
|
title: "S06. Return a File Download Response"
|
|
order: 25
|
|
status: "draft"
|
|
---
|
|
|
|
To force a browser to show a **download dialog** instead of rendering inline, send a `Content-Disposition` header. There's no special cpp-httplib API for this — it's just a header.
|
|
|
|
## Basic usage
|
|
|
|
```cpp
|
|
svr.Get("/download/report", [](const httplib::Request &req, httplib::Response &res) {
|
|
res.set_header("Content-Disposition", "attachment; filename=\"report.pdf\"");
|
|
res.set_file_content("reports/2026-04.pdf", "application/pdf");
|
|
});
|
|
```
|
|
|
|
`Content-Disposition: attachment` makes the browser pop up a "Save As" dialog. The `filename=` parameter becomes the default save name.
|
|
|
|
## Non-ASCII file names
|
|
|
|
For file names with non-ASCII characters or spaces, use the RFC 5987 `filename*` form.
|
|
|
|
```cpp
|
|
svr.Get("/download/report", [](const httplib::Request &req, httplib::Response &res) {
|
|
res.set_header(
|
|
"Content-Disposition",
|
|
"attachment; filename=\"report.pdf\"; "
|
|
"filename*=UTF-8''%E3%83%AC%E3%83%9D%E3%83%BC%E3%83%88.pdf");
|
|
res.set_file_content("reports/2026-04.pdf", "application/pdf");
|
|
});
|
|
```
|
|
|
|
The part after `filename*=UTF-8''` is URL-encoded UTF-8. Keep the ASCII `filename=` too, as a fallback for older browsers.
|
|
|
|
## Download dynamically generated data
|
|
|
|
You don't need a real file — you can serve a generated string as a download directly.
|
|
|
|
```cpp
|
|
svr.Get("/export.csv", [](const httplib::Request &req, httplib::Response &res) {
|
|
std::string csv = build_csv();
|
|
res.set_header("Content-Disposition", "attachment; filename=\"export.csv\"");
|
|
res.set_content(csv, "text/csv");
|
|
});
|
|
```
|
|
|
|
This is the classic pattern for CSV exports.
|
|
|
|
> **Note:** Some browsers will trigger a download based on Content-Type alone, even without `Content-Disposition`. Conversely, setting `inline` tries to render the content in the browser when possible.
|