getpass

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



NAME
       getpass - get a password

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

DESCRIPTION
       This function is obsolete.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
       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
       The function may fail if

       ENXIO  The process does not have a controlling terminal.

FILES
       /dev/tty

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

       ┌──────────┬───────────────┬────────────────┐
       │Interface Attribute     Value          │
       ├──────────┼───────────────┼────────────────┤
       │getpass() │ Thread safety │ MT-Unsafe term │
       └──────────┴───────────────┴────────────────┘
CONFORMING TO
       Present in SUSv2, but marked LEGACY.  Removed in POSIX.1-2001.

NOTES
       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
       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)

COLOPHON
       This page is part of release 5.03 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                             2019-03-06                        GETPASS(3)