GETPASS(3) Linux Programmer's Manual GETPASS(3)
getpass - get a password
char *getpass(const char *prompt);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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:
This function is obsolete.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
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
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 appropriately, and NULL is returned.
The function may fail if
ENXIO The process does not have a controlling terminal.
For an explanation of the terms used in this section, see at-
|Interface | Attribute | Value |
|getpass() | Thread safety | MT-Unsafe term |
Present in SUSv2, but marked LEGACY. Removed in POSIX.1-2001.
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-
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).
The calling process should zero the password as soon as possible to
avoid leaving the cleartext password visible in the process's address
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Linux 2019-03-06 GETPASS(3)
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