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)):

           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:

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       This function is obsolete.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 appropriately, and NULL is returned.

ERRORS         top

       The function may fail if

       ENXIO  The process does not have a controlling terminal.

FILES         top


ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │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

       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

SEE ALSO         top


COLOPHON         top

       This page is part of release 5.08 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

Linux                            2019-03-06                       GETPASS(3)

Pages that refer to this page: crypt(3)crypt_r(3)