PMC_CONFIGURE_LOGFILE(3)

💅 PMC_CONFIGURE_LOGFILE(3) — log file management, but make it make sense

okay bestie so this is PMC_CONFIGURE_LOGFILE(3) from the Library Functions Manual and it's genuinely so useful — it's all about wrangling log files for hwpmc(4) events 🎀

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✨ NAME ✨

pmc_configure_logfile, pmc_flush_logfile, pmc_writelog, pmc_close_logfile — log file management

📚 LIBRARY 📚

Performance Counters Library (libpmc, -lpmc) — yes you gotta link it, no cap 🔥

🫶 SYNOPSIS 🫶

#include <pmc.h>

int
pmc_configure_logfile(int fd);

int
pmc_flush_logfile(void);

int
pmc_writelog(uint32_t userdata);

int
pmc_close_logfile(void);

🌸 DESCRIPTION 🌸

so these four functions are the whole friend group that manages logging of hwpmc(4) events 💖 like that's their entire job and they ate.

Let me break down who does what, one icon at a time:

• pmc_configure_logfile(fd) turns logging on and off — main character energy, honestly. The way it works: if the argument fd is a valid file handle returned by a prior call to open(2) or socket(2), then performance events get logged to the file corresponding to that handle ✨ but if the value of fd is -1? Then logging gets stopped after any pending data is flushed. bye bestie 👋
• pmc_flush_logfile() forces ALL log data queued inside the hwpmc(4) driver to be written out. like it literally will not leave that data sitting in there, obsessed 😭
• pmc_writelog(userdata) appends a log entry containing the value of userdata to the log file. cute little custom note, love that for you 🦋
• pmc_close_logfile() flushes all pending log data and closes hwpmc(4)'s side of the stream. graceful exit, periodt 💅

⭐ RETURN VALUES ⭐

Upon successful completion, the value 0 is returned 🌈 otherwise the value -1 is returned and the global variable errno is set to indicate the error 🚨 like it's telling you exactly what went wrong, iykyk.

💀 ERRORS 💀

a call to pmc_configure_logfile() may fail with these, mmkay

• [EAGAIN] — the hwpmc(4) driver was not able to create a helper process due to system limits being reached 😮‍💨 (system said "no more helpers", rude)
• [EBUSY] — function pmc_configure_logfile() was called with a log file already configured 🙈 one at a time please!!
• [EINVAL] — function pmc_configure_logfile() was called with an argument of -1 without a log file being previously configured 💀 you can't stop what was never started, bestie
• [ENOMEM] — the system encountered a memory shortage when servicing this request 🍓 memory said "not today"

a call to pmc_flush_logfile() may fail with this one

• [EINVAL] — function pmc_flush_logfile() was called without a log file being previously configured 😭 pls configure first

a call to pmc_writelog() may fail with these two

• [EINVAL] — function pmc_writelog() was called without a log file being previously configured 🙈 same vibe, no log file, no entry
• [ENOMEM] — the system encountered a memory shortage when servicing this request 🍓 again with the memory shortage

ngl fam, the recurring theme here is: configure your log file first. the setup is the whole plot. ✨

👀 SEE ALSO 👀

• pmc(3)
• hwpmc(4)

the crossover episode you didn't know you needed 🧚

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that's the whole page bestie, go forth and log responsibly 💜

Debian — November 24, 2007 — pmc_configure_logfile(3), signing off 🎀