How can I read content from a file and use it as input for an ELF file

[AfalpHy]

I have written a test program as follows:

#include <stdio.h>

int main() {
    int a = 0;
    scanf("%d", &a);
    printf("output:%d\n", a);
    return 0;
}

I compiled it using the commandclang -target riscv64-linux-gnu -static test.c and executed the spike /riscv64-linux-gnu/bin/pk a.out command. Then, I manually entered 100, and it outputted the correct result 100, just like this:

$clang -target riscv64-linux-gnu -static test.c
$spike /riscv64-linux-gnu/bin/pk a.out
100
output:100

But when I used another command spike /riscv64-linux-gnu/bin/pk a.out < input.txt(the content of input.txt is 100), it didn't output the expected 100 but instead 0, just like this:

$spike /riscv64-linux-gnu/bin/pk a.out < input.txt
output:0

Is there an error in my usage? What should I do?

[jerryz123]

fd-0 (stdin) is redirected to the ns16550 UART device model, so piping data into spike via stdin will not work.

A fopen in your target program will work.

[AfalpHy]

Thanks for your reply.
I'm sorry that my question misled you. I don't want to change my test program, in other words, I don't want to use fopen. How can I pass the contents of a file to my program? Is it possible to achieve this by modifying the shell command（spike /riscv64-linux-gnu/bin/pk a.out < input.txt）?

[jerryz123]

No. Passing the contents of a file to your program is best done with fopen.

[AfalpHy]

OK. Thank you again for your reply.