getpass(3) Library Functions Manual getpass(3)
NAME
getpass - get a password
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#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
DESCRIPTION
This function is obsolete.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.
RETURN VALUE
The function getpass() returns a pointer to a static buffer containing
(the first PASS_MAX bytes of) the password without the trailing new-
line, 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.
ERRORS
ENXIO The process does not have a controlling terminal.
FILES
/dev/tty
ATTRIBUTES
For an explanation of the terms used in this section, see attrib-
utes(7).
┌────────────────────────────────────┬───────────────┬────────────────┐
│ Interface │ Attribute │ Value │
├────────────────────────────────────┼───────────────┼────────────────┤
│ getpass() │ Thread safety │ MT-Unsafe term │
└────────────────────────────────────┴───────────────┴────────────────┘
STANDARDS
None.
HISTORY
Version 7 AT&T UNIX. Present in SUSv2, but marked LEGACY. Removed in
POSIX.1-2001.
NOTES
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 dis-
abled.
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 ver-
sion 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)
Linux man-pages 6.7 2023-10-31 getpass(3)
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