getpass - get a password
char *getpass( const char * prompt );
This function is obsolete.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
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.
The function may fail if
The process does not have a controlling
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
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 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).
A getpass function appeared in Version 7 AT
The calling process should zero the password as soon as
possible to avoid leaving the cleartext password visible in
the process's address space.