Tcl_GetOpenFile(3tcl)

✨ NAME ✨

Tcl_GetOpenFile — bestie, this one hands you back a FILE* for a channel that's registered in the interpreter you pass in. 💅 Oh and, tiny detail: Unix only. Don't come for me, it's just the rules. 🫶

This lil page lives in the Tcl Library Procedures corner of the manual, and it's giving very "I know the file you're looking for" energy. 🔥

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🌸 SYNOPSIS 🌸

#include <tcl.h>

int
Tcl_GetOpenFile(interp, chanID, write, checkUsage, filePtr)

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🎀 ARGUMENTS 🎀

• Tcl_Interp *interp (in) — the Tcl interpreter you're pulling this file handle out of. That's the vibe check point. ✨
• const char *chanID (in) — a string that names the channel, like stdin or file4. Literally just the name, nothing extra. 💖
• int write (in) — non-zero means the file is gonna be used for writing, zero means it's gonna be used for reading. Pick a lane, bestie. 😌
• int checkUsage (in) — if this is non-zero, then you get an error generated when the file wasn't opened for the access mode that write is claiming. Snitch mode: on. 👑
• void **filePtr (out) — points to the word where we're gonna stash the pointer to the FILE structure for the file named by chanID. This is where the magic lands. 🦋

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🦋 DESCRIPTION 🦋

okay so. Tcl_GetOpenFile takes a file identifier — the kind of thing the open command hands you — and it drops a pointer to that file's FILE structure right into *filePtr. no cap. 💅

The write argument tells it whether you're gonna use that FILE pointer for reading or for writing. And here's the iconic part: in some cases — like when a channel is hooked up to a pipeline of subprocesses — you literally get different FILE pointers depending on whether you asked for reading or writing. the way that works is so real. 😭

Normally, Tcl_GetOpenFile returns TCL_OK. Slay. ✨

But if an error happens in Tcl_GetOpenFile — say chanID didn't make any sense, or checkUsage was set and the file wasn't opened for the access that write specified — then it returns TCL_ERROR, and the interpreter's result is gonna hold an error message. So check your result, bestie, fr fr. 💀

In the current implementation, checkUsage is ignored and consistency checks are always performed. So like... it's always checking. Always. 🙈

And one more time for the people in the back: this interface is only supported on the Unix platform. That's not me being dramatic, that's just the situation. 🌈

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⭐ KEYWORDS ⭐

channel, file handle, permissions, pipeline, read, write

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and that's the whole page, bestie!! 🎀 this is Tcl 8.0 energy from the Tcl Library Procedures section, so shoutout to Tcl_GetOpenFile(3tcl) — go get your FILE* and stay hydrated. mwah. 💖✨🫶