getpass(3) — Linux manual page

GETPASS(3)              Linux Programmer's Manual             GETPASS(3)

NAME         top

       getpass - get a password

SYNOPSIS         top

       #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 <= 2.19: */ _BSD_SOURCE
           Before glibc 2.2.2:
               none

DESCRIPTION         top

       This function is obsolete.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         top

       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.

ERRORS         top

       ENXIO  The process does not have a controlling terminal.

FILES         top

       /dev/tty

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       attributes(7).

       ┌───────────────────────────────┬───────────────┬────────────────┐
       │Interface                      │ Attribute     │ Value          │
       ├───────────────────────────────┼───────────────┼────────────────┤
       │getpass()                      │ Thread safety │ MT-Unsafe term │
       └───────────────────────────────┴───────────────┴────────────────┘

CONFORMING TO         top

       Present in SUSv2, but marked LEGACY.  Removed in POSIX.1-2001.

NOTES         top

       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         top

       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         top

       crypt(3)

COLOPHON         top

       This page is part of release 5.13 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/.

Linux                          2021-03-22                     GETPASS(3)

Pages that refer to this page: crypt(3)

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