---
name: "modbus_set_debug"
section: "3"
platform: "linux"
package: "libmodbus-dev"
version: "3.1.6-2.1"
release: "Debian 12 (Bookworm)"
platforms: ["linux"]
url: "https://new.carta.tech/modbus_set_debug"
---

# modbus\_set\_debug(3)

set debug flag of the context

## NAME

modbus\_set\_debug - set debug flag of the context

## SYNOPSIS

**int modbus\_set\_debug(modbus\_t \****ctx***, int** *flag***);**

## DESCRIPTION

The **modbus\_set\_debug()** function shall set the debug flag of the **modbus\_t** context by using the argument *flag*. By default, the boolean flag is set to FALSE. When the *flag* value is set to TRUE, many verbose messages are displayed on stdout and stderr. For example, this flag is useful to display the bytes of the Modbus messages.

```
[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>
```

## RETURN VALUE

The function shall return 0 if successful. Otherwise it shall return -1 and set errno.

## AUTHORS

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