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This function is obsolete.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 "password"), restores the terminal state and closes /dev/tty
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 <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).
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
Linux Manpage 2000-12-05 GETPASS(3)
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