getpass

GETPASS(3)                 Linux Programmer's Manual                GETPASS(3)



NAME
       getpass - get a password

SYNOPSIS
       #include <unistd.h>

       char *getpass( const char * prompt );

DESCRIPTION
       This function is obsolete. Do not use it.

       The  getpass() function opens /dev/tty (the controlling terminal of the
       process), outputs the string prompt, turns off echoing, reads one  line
       (the  "password"),  restores  the  terminal  state  and closes /dev/tty
       again.

RETURN VALUE
       The function getpass returns a pointer to a  static  buffer  containing
       the  (first  PASS_MAX  bytes of) the password without the trailing new-
       line, terminated by a NUL.  This buffer may be overwritten by a follow-
       ing  call.   On  error,  the  terminal  state is restored, errno is set
       appropriately, and NULL is returned.

ERRORS
       The function may fail if

       ENXIO  The process does not have a controlling terminal.

NOTES
       For libc4 and libc5, the prompt is  not  written  to  /dev/tty  but  to
       stderr.   Moreover,  if /dev/tty cannot be opened, the password is read
       from stdin.  The static buffer has length 128 so that  only  the  first
       127  bytes  of  the password are returned.  While reading the password,
       signal generation (SIGINT, SIGQUIT, SIGSTOP, SIGTSTOP) is disabled  and
       the  corresponding  characters (usually control-C, control-\, control-Z
       and control-Y) are transmitted as part of  the  password.   Since  libc
       5.4.19  also  line  editing is disabled, so that also backspace and the
       like will be seen as part of the password.

       For glibc2, if /dev/tty cannot be opened,  the  prompt  is  written  to
       stderr  and  the password is read from stdin.  There is no limit on the
       length of the password.  Line editing is not disabled.

       According to the SUSv2, the value of PASS_MAX must be defined in  <lim-
       its.h>  in  case  it is smaller than 8, and can in any case be obtained
       using sysconf(_SC_PASS_MAX).  However, POSIX.2 withdraws the  constants
       PASS_MAX  and  _SC_PASS_MAX,  and  the  function getpass ().  Libc4 and
       libc5 have never supported PASS_MAX or  _SC_PASS_MAX.   Glibc2  accepts
       _SC_PASS_MAX and returns BUFSIZ (e.g., 8192).

FILES
       /dev/tty

SEE ALSO
       crypt(3)

HISTORY
       A getpass function appeared in Version 7 AT&T UNIX.

BUGS
       The  calling  process  should  zero the password as soon as possible to
       avoid leaving the cleartext password visible in the  process's  address
       space.



Linux Manpage                     2000-12-05                        GETPASS(3)