GETPASS
Section: Linux Programmer's Manual (3)
Updated: 2019-03-06
Page Index
NAME
getpass - get a password
SYNOPSIS
#include <unistd.h>
char *getpass(const char *prompt);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
getpass():
-
- Since glibc 2.2.2:
-
_XOPEN_SOURCE && ! (_POSIX_C_SOURCE >= 200112L)
|| /* Glibc since 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE
- Before glibc 2.2.2:
-
none
DESCRIPTION
This function is obsolete.
Do not use it.
If you want to read input without terminal echoing enabled,
see the description of the
ECHO
flag in
termios(3).
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.
RETURN VALUE
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 null byte ('\0').
This buffer may be overwritten by a following call.
On error, the terminal state is restored,
errno
is set appropriately, and NULL is returned.
ERRORS
The function may fail if
- ENXIO
-
The process does not have a controlling terminal.
FILES
/dev/tty
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
| Interface | Attribute | Value
|
|
getpass()
| Thread safety | MT-Unsafe term
|
CONFORMING TO
Present in SUSv2, but marked LEGACY.
Removed in POSIX.1-2001.
NOTES
In the GNU C library implementation, 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 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().
The glibc version accepts
_SC_PASS_MAX
and returns
BUFSIZ
(e.g., 8192).
BUGS
The calling process should zero the password as soon as possible to avoid
leaving the cleartext password visible in the process's address space.
SEE ALSO
crypt(3)
COLOPHON
This page is part of release 5.10 of the Linux
man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
https://www.kernel.org/doc/man-pages/.