S6-FTRIGW(7)

💖 s6-ftrigw(7) — the notifier API, bestie edition 💖

okay so this one lives in the Miscellaneous Information Manual, and it's page S6-FTRIGW(7) — say hi 👋

✨ NAME ✨

s6-ftrigw — the API for notifiers, aka programs that just wanna regularly announce what they're doing to the whole world 📣 (well, to whoever's listening)

🦋 DESCRIPTION 🦋

So here's the vibe: notifiers are supposed to create an s6-fifodir(7) in a hardcoded place in the filesystem, and then document where that spot is like the good citizen they are, no cap. Then listeners can subscribe to that s6-fifodir(7) and catch the events as they drop. 🔥

check the s6/ftrigw.h header for the exact function prototypes — that's where the real receipts live, iykyk

🎀 Creating a fifodir

char const *path = "/var/lib/myservice/fifodir" ;
gid_t gid = -1 ;
int forceperms = 0 ;
int r = ftrigw_fifodir_make(path, gid, forceperms) ;

ftrigw_fifodir_make() creates an s6-fifodir(7) at the path location. ✨ And the return codes? Listen up:

• it returns 0, and sets errno, if something goes wrong 😭
• it returns 1 if it actually succeeds 🎉

Now for the spicy details:

• if an s6-fifodir(7) owned by the user already exists at path, and forceperms is zero, then ftrigw_fifodir_make() immediately returns success. easy slay 💅
• if forceperms is nonzero, then it tries to adjust path's permissions before returning. lowkey doing a little extra credit 🧚

And about gid, bestie, this is important:

• if gid is negative, then path gets created "public" — any listener at all will be able to subscribe to path. 🌈 open door policy
• if gid is nonnegative, then path is created "private" — only processes belonging to group gid will be able to subscribe to path. 🔒 members only

💜 Sending an event

char event = 'a' ;
r = ftrigw_notify(path, event) ;

ftrigw_notify() sends event to all the processes that are currently subscribed to path. 🫶 It returns −1 if an error occurs, or the number of successfully notified processes. So like, the count of people who actually got the message — very main character of it tbh 👑

🌸 Cleaning up

okay so this part is the "not me forgetting to clean my room" section 🙈 When stray KILL signals hit s6-ftrigrd(8) processes:

1. it's a sign of incorrect system administration — yeah, that's a yikes 💀
2. they can leave unused named pipes in the s6-fifodir(7)

And it's the s6-fifodir(7)'s owner's job — i.e. the notifier's job, so literally you — to periodically do some housecleaning and remove those unused pipes. 🧹✨

r = ftrigw_clean(path) ;

ftrigw_clean() cleans path. Returns 0, and sets errno, if it encounters an error 😭 and it returns 1 if it succeeds 🎉 periodt.

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⭐ SEE ALSO ⭐

• s6-accessrules(7)
• s6-fdholder(7)
• s6-ftrigr(7)
• s6-libs6(7)
• s6-s6lock(7)

This man page is ported from the authoritative documentation at: https://skarnet.org/software/s6/libs6/ftrigw.html 🦋

👑 AUTHORS 👑

• Laurent Bercot
• Alexis <flexibeast@gmail.com> (man page port)

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Debian 💖 September 29, 2021 💖 that's the source, version and date bestie, mwah 🫶 go notify someone about it ✨