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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:
               _BSD_SOURCE ||
                   (_XOPEN_SOURCE >= 500 ||
                       _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) &&
                   !(_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600)
           Before glibc 2.2.2: none

DESCRIPTION         top

       This function is obsolete.  Do not use it.

       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

       /dev/tty

CONFORMING TO         top

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

NOTES         top

       For libc4 and libc5, the prompt is not written to /dev/tty but to stderr.
       Moreover, if /dev/tty cannot be opened, the password is read from stdin.  The
       static buffer has length 128 so that only the first 127 bytes of the password
       are returned.  While reading the password, signal generation (SIGINT, SIGQUIT,
       SIGSTOP, SIGTSTP) is disabled and the corresponding characters (usually
       control-C, control-\, control-Z and control-Y) are transmitted as part of the
       password.  Since libc 5.4.19 also line editing is disabled, so that also
       backspace and the like will be seen as part of the password.

       For glibc2, 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 the 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().  Libc4 and libc5 have never
       supported PASS_MAX or _SC_PASS_MAX.  Glibc2 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 3.32 of the Linux man-pages project.  A
       description of the project, and information about reporting bugs, can be found
       at http://www.kernel.org/doc/man-pages/.

Linux                                 2010-09-20                           GETPASS(3)

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