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       getpass - get a password


       #include <unistd.h>

       char *getpass( const char *prompt);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

           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:


       This  function  is  obsolete.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.


       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.


       The function may fail if

       ENXIO  The process does not have a controlling terminal.




   Multithreading (see pthreads(7))
       The getpass() function is not thread-safe.


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


       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

       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).


       The  calling  process  should  zero  the password as soon as possible to avoid leaving the
       cleartext password visible in the process's address space.




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