How can I use curl with a file descriptor for better performance? or Is there a way to handle curl us

Subject: Can curl read/write directly from a file descriptor? Need help!

Hey folks,

I’ve been messing around with curl using file descriptor instead of temp files, but I’m kinda stuck.

Like, I know you can pipe stuff in/out, but is there a *direct* way to make curl using file descriptor work? I’m trying to avoid the whole "write to disk, read back" dance for performance reasons.

Found some docs mentioning `-T -` for uploads and `-o -` for outputs, but what if I wanna use an actual fd number?

Also, why would someone prefer curl using file descriptor over regular files? Just speed, or are there other perks?

Any tips or gotchas? My scripts are getting messy with temp files, and I’d love to clean ‘em up.

Thanks in advance!

—

*PS: Sorry if this is a noob question, still getting the hang of advanced curl tricks.*

Hey! Yeah, curl using file descriptor is totally doable. You can use `/dev/fd/N` where N is your fd number. Like, for fd 3, try `-T /dev/fd/3` for uploads.

Works on Unix-like systems, but Windows might be tricky.

Also, the big perk? No disk I/O overhead. Faster and cleaner, especially if you're handling sensitive data and don’t wanna leave temp files lying around.

Check out the curl man page (search for "file descriptor")—kinda buried but it’s there.

Not a noob question at all! Curl using file descriptor is a power move.

For reads, you can do `-d @/dev/fd/3` or similar.

Why bother? Temp files are messy, and if you’re dealing with pipes or process substitution, fds keep everything in memory. Plus, no cleanup!

One gotcha: make sure the fd is open and readable/writable before curl touches it. Otherwise, 💥.

Man, I feel you on the temp file clutter. For curl using file descriptor, try:

```bash
exec 3<> myfile.txt
curl -T /dev/fd/3 http://example.com
```

Speed’s the main win, but it’s also about elegance. Fewer moving parts == fewer bugs.

If you’re scripting, this is way more robust than `mktemp` nonsense.

Oh, this is fun! You can even use `-K` with a config file pointing to `/dev/fd/N`.

Example:
```
url = "http://example.com"
upload-file = "/dev/fd/3"
```

Why? Less filesystem noise, better for chaining commands.

Downside: Debugging can be a pain since you’re not leaving intermediate files.

For curl using file descriptor, you might wanna peek at `--data-urlencode` too if you’re passing stuff around.

But yeah, `/dev/fd/` is your friend. Just remember: not all shells handle fds the same. Bash? Cool. Zsh? Cool. Dash? Maybe not.

Perks? Performance, yeah, but also security—no temp file means no accidental leaks.

Hey all, thanks for the killer tips! Tried the `/dev/fd/3` trick and it worked like a charm.

One follow-up: What if I’m passing data between two curl commands? Like, can I pipe directly into another curl using file descriptor without a named pipe?

Also, big shoutout for the security angle—didn’t even think about temp file leaks. Y’all rock.

Pro tip: Combine curl using file descriptor with `<( )` process substitution. Like:

```bash
curl -d @<(grep "stuff" myfile) http://example.com
```

No fd number needed, but same idea—no temp files.

Gotchas? Uh, make sure your data isn’t too big for pipes. Buffering can bite you.

If you’re on Linux, `procfs` is your backup: `/proc/self/fd/N`. Same as `/dev/fd/N` but works even if `/dev/fd` isn’t mounted.

Why prefer fds? Besides speed, it’s atomic. No partial writes or race conditions like with temp files.

Docs are sparse, but the curl mailing list has some gems.

curl using file descriptor is *chef’s kiss* for scripting.

For outputs:
```bash
exec 3> output.txt
curl -o /dev/fd/3 http://example.com
```

Cleaner than `>>` and no risk of truncation.

Bonus: Works great with `lsof` if you need to debug what’s holding the fd open.