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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | FILES | ATTRIBUTES | STANDARDS | HISTORY | NOTES | BUGS | SEE ALSO | COLOPHON |
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getpass(3) Library Functions Manual getpass(3)
getpass - get a password
Standard C library (libc, -lc)
#include <unistd.h>
[[deprecated]] 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 >= 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE
Before glibc 2.2.2:
none
This function is obsolete. Do not use it. See NOTES. 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.
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 to indicate the error, and NULL is
returned.
ENXIO The process does not have a controlling terminal.
/dev/tty
For an explanation of the terms used in this section, see
attributes(7).
┌───────────────────────────────┬───────────────┬────────────────┐
│ Interface │ Attribute │ Value │
├───────────────────────────────┼───────────────┼────────────────┤
│ getpass() │ Thread safety │ MT-Unsafe term │
└───────────────────────────────┴───────────────┴────────────────┘
None.
Version 7 AT&T UNIX. Present in SUSv2, but marked LEGACY.
Removed in POSIX.1-2001.
You should use instead readpassphrase(3bsd), provided by libbsd.
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).
The calling process should zero the password as soon as possible
to avoid leaving the cleartext password visible in the process's
address space.
crypt(3)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
[email protected]
Linux man-pages 6.15 2025-05-17 getpass(3)
Pages that refer to this page: crypt(3)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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