Originální popis anglicky:
getpass - get a password
Návod, kniha: Linux Programmer's Manual
#include <unistd.h>
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This function is obsolete.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 "password"), restores the terminal state and closes
/dev/tty again.
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
- ENXIO
- The process does not have a controlling terminal.
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).
/dev/tty
crypt(3)
A
getpass function appeared in Version 7 AT&T UNIX.
The calling process should zero the password as soon as possible to avoid
leaving the cleartext password visible in the process's address space.
