Open Source Software

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   This  function  is obsolete.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 4.09 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/.



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