---
name: "modbus_read_input_registers"
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_read_input_registers"
---

# modbus\_read\_input\_registers(3)

read many input registers

## NAME

modbus\_read\_input\_registers - read many input registers

## SYNOPSIS

**int modbus\_read\_input\_registers(modbus\_t \****ctx***, int** *addr***, int** *nb***, uint16\_t \****dest***);**

## DESCRIPTION

The **modbus\_read\_input\_registers()** function shall read the content of the *nb* input registers to address *addr* of the remote device. The result of the reading is stored in *dest* array as word values (16 bits).

You must take care to allocate enough memory to store the results in *dest* (at least *nb* \* sizeof(uint16\_t)).

The function uses the Modbus function code 0x04 (read input registers). The holding registers and input registers have different historical meaning, but nowadays it’s more common to use holding registers only.

## RETURN VALUE

The function shall return the number of read input registers if successful. Otherwise it shall return -1 and set errno.

## ERRORS

**EMBMDATA**

Too many bits requested

## SEE ALSO

[**modbus\_read\_input\_bits**(3)](/modbus_read_input_bits/3.md) [**modbus\_write\_register**(3)](/modbus_write_register/3.md) [**modbus\_write\_registers**(3)](/modbus_write_registers/3.md)

## AUTHORS

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