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getlogin(3) [bsd man page]

GETLOGIN(3)						     Library Functions Manual						       GETLOGIN(3)

NAME
getlogin - get login name SYNOPSIS
char *getlogin() DESCRIPTION
Getlogin returns a pointer to the login name as found in /var/run/utmp. It may be used in conjunction with getpwnam to locate the correct password file entry when the same userid is shared by several login names. If getlogin is called within a process that is not attached to a terminal, or if there is no entry in /var/run/utmp for the process's ter- minal, getlogin returns a NULL pointer (0). A reasonable procedure for determining the login name is to first call getlogin and if it fails, to call getpwuid(getuid()). FILES
/var/run/utmp SEE ALSO
getpwent(3), utmp(5), ttyslot(3) DIAGNOSTICS
Returns a NULL pointer (0) if name not found. BUGS
The return values point to static data whose content is overwritten by each call. 7th Edition November 27, 1996 GETLOGIN(3)

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GETLOGIN(2)						      BSD System Calls Manual						       GETLOGIN(2)

NAME
getlogin, setlogin -- get/set login name SYNOPSIS
#include <unistd.h> char * getlogin(void); int setlogin(const char *name); DESCRIPTION
The getlogin() routine returns the login name of the user associated with the current session, as previously set by setlogin(). The name is normally associated with a login shell at the time a session is created, and is inherited by all processes descended from the login shell. (This is true even if some of those processes assume another user ID, for example when su(1) is used.) Setlogin() sets the login name of the user associated with the current session to name. This call is restricted to the super-user, and is normally used only when a new session is being created on behalf of the named user (for example, at login time, or when a remote shell is invoked). RETURN VALUES
If a call to getlogin() succeeds, it returns a pointer to a null-terminated string in a static buffer. If the name has not been set, it returns NULL. If a call to setlogin() succeeds, a value of 0 is returned. If setlogin() fails, a value of -1 is returned and an error code is placed in the global location errno. ERRORS
The following errors may be returned by these calls: [EFAULT] The name parameter gave an invalid address. [EINVAL] The name parameter pointed to a string that was too long. Login names are limited to MAXLOGNAME (from <sys/param.h>) characters, currently 12. [EPERM] The caller tried to set the login name and was not the super-user. SEE ALSO
setsid(2) BUGS
Login names are limited in length by setlogin(). However, lower limits are placed on login names elsewhere in the system (UT_NAMESIZE in <utmp.h>). In earlier versions of the system, getlogin() failed unless the process was associated with a login terminal. The current implementation (using setlogin()) allows getlogin to succeed even when the process has no controlling terminal. In earlier versions of the system, the value returned by getlogin() could not be trusted without checking the user ID. Portable programs should probably still make this check. HISTORY
The getlogin() function first appeared in 4.4BSD. 4.2 Berkeley Distribution June 9, 1993 4.2 Berkeley Distribution

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