error when compiling

[Setoula]

C:\Users\bAppData\Local\Temp\ccb469Tf.ltrans0.ltrans.o:(.rodata+0x6): undefined reference to Print::write(unsigned char const*, unsigned int)' c:/users/b/appdata/local/arduino15/packages/arduino/tools/avr-gcc/7.3.0-atmel3.6.1-arduino7/bin/../lib/gcc/avr/7.3.0/../../../../avr/lib/avr5/crtatmega328p.o:(.init9+0x0): undefined reference to main'
collect2.exe: error: ld returned 1 exit status

exit status 1

Compilation error: exit status 1

[greiman]

I have no idea how this involves SdFat.

[brightproject]

C:\Users\bAppData\Local\Temp\ccb469Tf.ltrans0.ltrans.o:(.rodata+0x6): undefined reference to Print::write(unsigned char const*, unsigned int)' c:/users/b/appdata/local/arduino15/packages/arduino/tools/avr-gcc/7.3.0-atmel3.6.1-arduino7/bin/../lib/gcc/avr/7.3.0/../../../../avr/lib/avr5/crtatmega328p.o:(.init9+0x0): undefined reference to main' collect2.exe: error: ld returned 1 exit status

exit status 1

Compilation error: exit status 1

It's really hard to help you without knowing what microcontroller, what IDE and what framework you're using.
I've had this happen when building code for a framework

https://github.com/platformio/platform-ststm32

Then I used a project that was written for Linux and required opening files.

https://github.com/orgs/stm32duino/discussions/2523

You seem to have something to do with the main file, again, write more input data and the task will become clearer🙂