|GETLOGIN(3C)||Standard C Library Functions||GETLOGIN(3C)|
#include <unistd.h> char *getlogin(void);
char *getlogin_r(char *name, int namelen);
cc [ flag ... ] file... -D_POSIX_PTHREAD_SEMANTICS [ library ... ] int getlogin_r(char *name, size_t namesize);
The login name plus the terminating null byte can be up to 33 characters in length. Newly-compiled programs should use the LOGIN_NAME_MAX symbol, defined in <limits.h>, to size the buffer. Older programs that call getlogin() expect only the legacy 9-character length. These automatically link to a version of the getlogin() functions that truncates longer login names. It's also possible to compile new programs that link to truncating versions of these functions by defining __USE_LEGACY_LOGNAME__ in the compile environment.
Some older programs will correctly handle long login names returned by the getlogin() function. For this case, the user compatibility library /usr/lib/getloginx.so.1 redirects to a version of the getlogin() function that returns the long name. This library should be added to such an application at runtime using LD_PRELOAD.
If getlogin() is called within a process that is not attached to a terminal, it returns a null pointer. The correct procedure for determining the login name is to call cuserid(3C), or to call getlogin() and if it fails to call getpwuid(3C).
The getlogin_r() function has the same functionality as getlogin() except that the caller must supply a buffer name with length namelen to store the result. The name buffer should be at least LOGIN_NAME_MAX bytes in size (defined in <limits.h>). The POSIX version (see standards(5)) of getlogin_r() takes a namesize parameter of type size_t. If the size of the supplied buffer is less than the size of LOGIN_NAME_MAX and the name, including the null terminator, does not fit inside the buffer, than an error will be generated. Otherwise, the buffer name will be updated with the login name.
The standard-conforming getlogin_r() returns 0 if successful, or the error number upon failure.
The getlogin() and getlogin_r() functions may fail if:
The getlogin_r() function may fail if:
Three names associated with the current process can be determined: getpwuid(geteuid()) returns the name associated with the effective user ID of the process; getlogin() returns the name associated with the current login activity; and getpwuid(getuid()) returns the name associated with the real user ID of the process.
|ATTRIBUTE TYPE||ATTRIBUTE VALUE|
The getlogin() function is safe to use in multithreaded applications, but is discouraged. The getlogin_r() function should be used instead.
Solaris 2.4 and earlier releases provided a getlogin_r() as specified in POSIX.1c Draft 6. The final POSIX.1c standard changed the interface as described above. Support for the Draft 6 interface is provided for compatibility only and may not be supported in future releases. New applications and libraries should use the standard-conforming interface.
|March 15, 2014|