linux man page for getpass

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

NAME
       getpass - get a password

SYNOPSIS
       #include <unistd.h>

       char *getpass( const char *prompt);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       getpass():
	   Since glibc 2.2.2:
	       _BSD_SOURCE ||
		   (_XOPEN_SOURCE >= 500 ||
		       _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) &&
		   !(_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600)
	   Before glibc 2.2.2: none

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       This function is obsolete.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  null byte ('').  This buffer may be overwritten by a following 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.

FILES
       /dev/tty

CONFORMING TO
       Present in SUSv2, but marked LEGACY.  Removed in POSIX.1-2001.

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, SIGTSTP) 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 <limits.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).

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.

SEE ALSO
       crypt(3)

COLOPHON
       This page is part of release 3.27 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2010-09-20								GETPASS(3)