Hello Charles, On Friday, April 2, 2004 at 6:21:55 AM you wrote (at least in part):
>>> I hope this isn't some kind of bitmasking thing, because that just >>> makes my head spin. >> That is exactly what it is... > So how does one deal with that? Carefully. > How does this work? Good. :-) OK, an example: PW_GID is set to 44 (0x2C), that's 0x04 + 0x08 + 0x20, means NO_WEBMAIL, NO_IMAP & NO_RELAY. To figure if the user is set to NO_DIALUP check: PW_GID & 64 (0x40 for NO_DIALUP): 44 & 64 = 0 0x2C & 0x40 = 0 Or in binary notation: 00101100 & 01000000 ========== 00000000 = 0x00 == 0 decimal. So this user has not NO_DIALUP set. No imagine a user set to NO_DIALUP, NO_WEBMAIL and NO_RELAY: 0x04 + 0x20 + 0x40 = 0x64 4 + 32 + 64 = 100 (decimal) PW_GID & 64 (0x40 for NO_DIALUP): 100 & 64 = 64 (decimal) 0x64 & 0x40 = 0x40 01100100 & 01000000 ========== 01000000 = 0x40 == 64 decimal. So to see if a flag is set AND operate on PW_GID and FLAG and see if the result is different from zero. As every flag gets a different bit assigned this bit, and only this bit, will be set when you AND operate and this bit was set in PW_GID's value. In cat it is really quite easy to handle and most programming languages should be able to bit-operate with integer values too. So you wouldn't even have to convert PW_GID into a "real bitmask", in fact the integer already is one: just use an arbitrary calculator to translate an arbitrary decimal value into binary representation. No "translate" all the hex values for different flags into binary and you'll see: they all have /exactly/ one bit set to 1. Not more, not less. And this is all about how it works :-) HTH -- Best regards Peter Palmreuther Once a job is fouled up, anything done to improve it only makes it worse.
