cc -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations fcntl/O_RSYNC.c -o fcntl/O_RSYNC -D_POSIX_C_SOURCE=202405L  -lm -lpthread  -liconv
fcntl/O_RSYNC.c:4:2: error: "O_RSYNC is not defined"
    4 | #error "O_RSYNC is not defined"
      |  ^
1 error generated.