Numerical values of open arguments in linux

Question

I am looking at the linux manual for the open function here but I am not able to find the integer values to the various flags such as O_WRONLY, O_CREAT, O_RDONLY . Is there a way to find this information?

Answer 1

Here's how I found the definitions:

$ find /usr/include -type f -name '*.h' -exec grep -E '^#define.*O_(WRONLY|RDONLY|RDWR)' {} +
/usr/include/asm-generic/fcntl.h:#define O_RDONLY   00000000
/usr/include/asm-generic/fcntl.h:#define O_WRONLY   00000001
/usr/include/asm-generic/fcntl.h:#define O_RDWR     00000002
/usr/include/x86_64-linux-gnu/bits/fcntl-linux.h:#define O_RDONLY        00
/usr/include/x86_64-linux-gnu/bits/fcntl-linux.h:#define O_WRONLY        01
/usr/include/x86_64-linux-gnu/bits/fcntl-linux.h:#define O_RDWR          02