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\"     @(#)getpass.3    8.1 (Berkeley) 6/4/93
\"
Dd April 13, 2012
Dt GETPASS 3
Os
Sh NAME
Nm getpass ,
Nm getpass_r ,
Nm getpassfd
Nd get a password
Sh LIBRARY
Lb libc
Sh SYNOPSIS
In unistd.h
Ft char *
Fn getpass "const char *prompt"
Ft char *
Fn getpass_r "const char *prompt" "char *buf" "size_t buflen"
Ft char *
Fn getpassfd "const char *prompt" "char *buf" "size_t buflen" "int *fd" "int flags" "int timeout"
Sh DESCRIPTION
The
Fn getpass
function displays a prompt to, and reads in a password from,
Pa /dev/tty .
If this file is not accessible,
Fn getpass
displays the prompt on the standard error output and reads from the standard
input.
Pp
The password may be up to
Xr sysconf 3
Dv _SC_PASS_MAX
characters in length.
Any additional
characters and the terminating newline character are discarded.
Pp
Fn getpass
turns off character echoing while reading the password.
Pp
Fn getpass_r
is similar to
Fn getpass
only it puts its result in
Fa buf
for up to
Fa buflen
characters.
If the
Fa buf
argument is
Dv NULL ,
then a buffer will be dynamically allocated.
Pp
The
Fn getpassfd
function allows one to specify the three file descriptors corresponding to
Dv stdin ,
Dv stdout ,
and
Dv stderr
in the
Fa fd
argument, or if
Fa fd
is
Dv NULL ,
Fn getpassfd
first attempts to open
Pa /dev/tty
and if that fails, defaults to
Dv STDIN_FILENO
for input and
Dv STDERR_FILENO
for output.
Pp
The behavior of
Fn getpassfd
is controlled by the
Fa flags
argument:
Bl -tag -width GETPASS_FORCE_UPPER
It Dv GETPASS_NEED_TTY
Fail if we are unable to set the tty modes like we want.
It Dv GETPASS_FAIL_EOF
Fail if we get the end-of-file character instead of returning the result so far.
It Dv GETPASS_BUF_LIMIT
Beep when the buffer limit is reached, instead of silently absorbing it.
It Dv GETPASS_NO_SIGNAL
Don't make ttychars send signals.
It Dv GETPASS_NO_BEEP
Don't beep if we erase past the beginning of the buffer or we try to enter past
the end.
It Dv GETPASS_ECHO_STAR
Echo a
Sq *
for each character entered.
It Dv GETPASS_ECHO
Echo characters as they are typed.
It Dv GETPASS_ECHO_NL
Echoes a newline if successful.
It Dv GETPASS_7BIT
Mask the high bit for each entered character.
It Dv GETPASS_FORCE_LOWER
Lowercase each entered character.
It Dv GETPASS_FORCE_UPPER
Uppercase each entered character.
El
Pp
Finally if the
Fa timeout
argument is non zero,
Fn getpassfd
will wait for
Fa timeout
seconds for input after each character before returning an error, instead of
waiting forever.
Sh RETURN VALUES
The
Fn getpass
function returns a pointer to the NUL terminated password, or an empty
string on error.
The
Fn getpass_r
and
Fn getpassfd
functions return a pointer to the NUL terminated password, or
Dv NULL
on error.
Sh FILES
Bl -tag -width /dev/tty -compact
It Pa /dev/tty
El
Sh SEE ALSO
Xr crypt 3
Sh STANDARDS
The
Fn getpass
function appeared in
St -susv2 ,
but it was already marked as legacy.
The function was removed in the
St -p1003.1-2001
standard.
Sh HISTORY
A
Fn getpass
function appeared in
At v7 .
The
Fn getpass_r
and
Fn getpassfd
functions appeared in
Nx 7.0 .
Sh BUGS
The
Fn getpass
function leaves its result in an internal static object and returns
a pointer to that object.
Subsequent calls to
Fn getpass
will modify the same object.
Sh SECURITY CONSIDERATIONS
The calling process should zero the password as soon as possible to
avoid leaving the cleartext password visible in the process's address
space.
Pp
Historically
Nm
accepted and returned a password if it could not modify the terminal
settings to turn echo off (or if the input was not a terminal).
In this implementation, only terminal input is accepted.

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