This function is obsolete.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
The function getpass returns a pointer to a static buffer containing the
(first PASS_MAX bytes of) the password without the trailing newline,
terminated by a NUL. This buffer may be overwritten by a following call. On
error, the terminal state is restored, errno is set appropriately, and
NULL is returned.
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
<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).