MODBUS_SET_DEBUG(3)

💅 MODBUS_SET_DEBUG 💅

okay bestie, welcome to the modbus_set_debug page of the libmodbus Manual — manual section 3, the library-call girlies, iykyk ✨

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🌸 NAME 🌸

modbus_set_debug — sets the debug flag on the context, periodt 🎀

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🦋 SYNOPSIS 🦋

int modbus_set_debug(modbus_t *ctx, int flag);

that's it. that's the whole signature. she's small but she's powerful 💖

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✨ DESCRIPTION ✨

So here's the vibe: the modbus_set_debug() function shall set the debug flag of the modbus_t context, using the argument flag. Yes bestie, that's the whole job. She sets a flag. She's not doing your taxes. 🌸

By default, the boolean flag is set to FALSE. Chill. Silent. Unbothered. ✨

When the flag value is set to TRUE, many verbose messages are displayed on stdout and stderr. Like, she starts yapping. A lot. But in a useful way!! 🫶 For example, this flag is useful to display the bytes of the Modbus messages. Byte reveal moment. The hex is giving main character energy 💅

[00][14][00][00][00][06][12][03][00][6B][00][03]
Waiting for a confirmation...
<00><14><00><00><00><09><12><03><06><02><2B><00><00><00><00>

look at her go 😭 all those little bytes just vibing in square brackets and angle brackets, and then a whole "Waiting for a confirmation..." in the middle like she's texting and left you on read 🍓

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🔥 RETURN VALUE 🔥

The function shall return 0 if successful. Slay. We love a zero. Zero is the good one here, don't get it twisted ✨

Otherwise it shall return -1 and set errno. So if you see that -1 bestie, go check errno — she left you a note 💌

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👑 AUTHORS 👑

The libmodbus documentation was written by Stéphane Raimbault <stephane.raimbault@gmail.com> 💜

like, the literal icon who wrote all this down for us. respect. 🙇‍♀️

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okay quick vibe check before you go: this page is for MODBUS_SET_DEBUG(3) from libmodbus v3.1.6, dated 11/17/2025 🎀 go forth and turn that flag on when your bytes are acting sus, bestie. bye!! 💖✨🦋