GETPASS(3) BSD Library Functions Manual GETPASS(3)NAME
getpass — get a password
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <unistd.h>
char *
getpass(const char *prompt);
char *
getpass_r(const char *prompt, char *buf, size_t buflen);
char *
getpassfd(const char *prompt, char *buf, size_t buflen, int *fd,
int flags, int timeout);
DESCRIPTION
The getpass() function displays a prompt to, and reads in a password
from, /dev/tty. If this file is not accessible, getpass() displays the
prompt on the standard error output and reads from the standard input.
The password may be up to sysconf(3) _SC_PASS_MAX characters in length.
Any additional characters and the terminating newline character are dis‐
carded.
getpass() turns off character echoing while reading the password.
getpass_r() is similar to getpass() only it puts its result in buf for up
to buflen characters. If the buf argument is NULL, then a buffer will be
dynamically allocated.
The getpassfd() function allows one to specify the three file descriptors
corresponding to stdin, stdout, and stderr in the fd argument, or if fd
is NULL, getpassfd() first attempts to open /dev/tty and if that fails,
defaults to STDIN_FILENO for input and STDERR_FILENO for output.
The behavior of getpassfd() is controlled by the flags argument:
GETPASS_NEED_TTY Fail if we are unable to set the tty modes like we
want.
GETPASS_FAIL_EOF Fail if we get the end-of-file character instead of
returning the result so far.
GETPASS_BUF_LIMIT Beep when the buffer limit is reached, instead of
silently absorbing it.
GETPASS_NO_SIGNAL Don't make ttychars send signals.
GETPASS_NO_BEEP Don't beep if we erase past the beginning of the
buffer or we try to enter past the end.
GETPASS_ECHO_STAR Echo a ‘*’ for each character entered.
GETPASS_ECHO Echo characters as they are typed.
GETPASS_ECHO_NL Echoes a newline if successful.
GETPASS_7BIT Mask the high bit for each entered character.
GETPASS_FORCE_LOWER Lowercase each entered character.
GETPASS_FORCE_UPPER Uppercase each entered character.
Finally if the timeout argument is non zero, getpassfd() will wait for
timeout seconds for input after each character before returning an error,
instead of waiting forever.
RETURN VALUES
The getpass() function returns a pointer to the NUL terminated password,
or an empty string on error. The getpass_r() and getpassfd() functions
return a pointer to the NUL terminated password, or NULL on error.
FILES
/dev/tty
SEE ALSOcrypt(3)STANDARDS
The getpass() function appeared in Version 2 of the Single UNIX
Specification (“SUSv2”), but it was already marked as legacy. The func‐
tion was removed in the IEEE Std 1003.1-2001 (“POSIX.1”) standard.
HISTORY
A getpass() function appeared in Version 7 AT&T UNIX. The getpass_r()
and getpassfd() functions appeared in NetBSD 7.0.
BUGS
The getpass() function leaves its result in an internal static object and
returns a pointer to that object. Subsequent calls to getpass() will
modify the same object.
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.
Historically getpass 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.
BSD April 13, 2012 BSD
