10-28-2003
The user name will be in the environment and you can get it with getenv(). The environment variable will be called either USER or LOGNAME. (Posix requires LOGNAME) Whichever variable your system uses, it is set by the login program. And a decent cron will also set it for cron and "at" jobs. It won't get set if the user invokes your program via a remote service that did not properly log him in. But a clever user can set the env variable himself in that case. Which bring up a problem....a user could also clobber the variable, intentionally or otherwise.
Another approach is the inspect fd's 0, 1, and 2. They may be connected to the user's tty. isatty() can tell you if they are tty's or not. And ttyname() can provide the name of the tty. Once you have that, you can search the utmp file via getutmp() to get the user name as recorded by the login (or similiar) program. Again, not all remote services will set a utmp entry. And this will fail for cron or "at" jobs. This is how "who am i" works. And it is why
who am i < /dev/null 2 > /dev/null | cat
fails.
Another approach is to get the uid of the process with getuid() and then scan the passwd file via getpwnam(). This is how the program whoami works. But if user A signs on and su's to user B and then runs your program, you get user B.
As for the password, you can't get that. And I wonder why you want it.
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utmp(5) File Formats Manual utmp(5)
Name
utmp, wtmp - login records
Syntax
#include <utmp.h>
Description
The file records information about who is currently using the system. The file is a sequence of entries with the following structure
declared in the include file:
struct utmp {
char ut_line[8]; /* tty name */
char ut_name[8]; /* user id */
char ut_host[16]; /* host name, if remote */
long ut_time; /* time on */
};
This structure gives the name of the special file associated with the user's terminal, the user's login name, and the time of the login in
the form of
The file records all logins and logouts. A null user name indicates a logout on the associated terminal. A terminal referenced with a
tilde (~) indicates that the system was rebooted at the indicated time. The adjacent pair of entries with terminal names referenced by a
vertical bar (|) or a right brace (}) indicate the system-maintained time just before and just after a command has changed the system's
timeframe.
The file is maintained by and Neither of these programs creates the file, so, if it is removed, record-keeping is turned off. It is summa-
rized by
Files
See Also
last(1), lastcomm(1), login(1), who(1), ac(8), init(8)
utmp(5)