$ dd bs=1M count=10 </dev/urandom >random_file
10485760 bytes (10 MB, 10 MiB) copied, 0.183075 s, 57.3 MB/s

$ clang -O3 cp_x.c -o cp_x

$ time ./cp_x random_file random_file_copy

Can we get any insights from strace?
$strace ./cp_x random_file random_file_copy



cp command
real    0m0.071s
user    0m0.005s
sys     0m0.023s


cp_fgetc (stdio)
real    0m0.084s
user    0m0.069s
sys     0m0.010s

cp_libc_one_byte (read/write)
real    0m0.084s
user    0m0.069s
sys     0m0.010s

cp_libc (read/write) 4096 bytes