__getlogin1() — Get the user login name

Standards

Standards / Extensions	C or C++	Dependencies
POSIX.1 XPG4 XPG4.2	both

Format

_POSIX_SOURCE:

#define _POSIX_SOURCE
#include <unistd.h>

char *__getlogin1(void);

General description

Finds the name that the login process associated with the current terminal. If called from batch, __getlogin1() finds the name associated with the batch program. With z/OS® UNIX services, this name is a TSO/E user ID unless the USERIDALISTABLE is in use. If the USERIDALISTABLE is setup and a z/OS UNIX alias name exists for a given MVS(TSO, batch user, etc.) userid, then that will be returned.

If __getlogin1() cannot determine the login name, you can call getuid() to get the user ID of the process, and then call getpwuid() to get a login name associated with that user ID. getpwuid() always returns the passwd struct for the same user, even if multiple users have the same UID.

Returned value

If successful, __getlogin1() returns a pointer to a string that has the login name for the current terminal.

If unsuccessful, __getlogin1() returns the NULL pointer.

There are no documented errno values.

Example

CELEBG12

/* CELEBG12

   This example gets the user login name.

 */
#define _POSIX_SOURCE
#include <stdio.h>
#include <unistd.h>

main() {
  char *user;

  if ((user = __getlogin1()) == NULL)
    perror("__getlogin1() error");
  else printf("__getlogin1() returned %s\n", user);
}

Output

getlogin() returned MEGA