44 lines
1.6 KiB
C
44 lines
1.6 KiB
C
#include "ulib.h"
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/*
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* Left half of shell.c's new `cmd1 | cmd2` pipeline syntax's live demo.
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* jobctlSpawnPiped (jobctl.h) bakes a real pipe end into this process's own
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* fd 1 BEFORE it ever runs a single instruction (vfsPipeAttachInto, vfs.h)
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* -- from this program's own point of view it writes its stdout exactly
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* like any well-behaved Unix filter, with no idea a pipe is on the other
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* end instead of the real console. fd 2 (stderr) is deliberately left
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* alone by the pipeline setup (only fd 0/fd 1 are ever redirected, matching
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* a real shell), so the diagnostic lines below go straight to the real
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* console even though fd 1's own payload does not -- writing them through
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* fd 1 instead (print()/printDec(), ulib.h, both hardcoded to fd 1) would
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* corrupt the exact payload pipesink.c compares against.
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*
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* Deliberately writes once and exits immediately: pipesink.c's own
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* blocking read has to notice the resulting EOF (this process's own exit
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* reclaims its fd 1, dropping the pipe's writer count to 0 -- see
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* sched.c's reclaimOpenFds) the same way every other pipe/fifo EOF demo in
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* this kernel already does, not just receive the payload.
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*/
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#define pipelinePayload "pipeline-payload-ok"
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static void printErr(const char* text)
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{
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userWrite(2, text, stringLength(text));
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}
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int main(void)
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{
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printErr("pipesrc: writing payload to stdout (pipe)\n");
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unsigned long length = stringLength(pipelinePayload);
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long written = userWrite(1, pipelinePayload, length);
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if (written != (long)length) {
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printErr("pipesrc: FAIL short/failed write\n");
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return 1;
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}
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printErr("pipesrc: wrote payload\n");
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return 0;
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}
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