getpass(3)

1getpass(3)                 Library Functions Manual                 getpass(3)
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NAME

6       getpass - get a password
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LIBRARY

9       Standard C library (libc, -lc)
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SYNOPSIS

12       #include <unistd.h>
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14       [[deprecated]] char *getpass(const char *prompt);
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16   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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18       getpass():
19           Since glibc 2.2.2:
20               _XOPEN_SOURCE && ! (_POSIX_C_SOURCE >= 200112L)
21                   || /* glibc >= 2.19: */ _DEFAULT_SOURCE
22                   || /* glibc <= 2.19: */ _BSD_SOURCE
23           Before glibc 2.2.2:
24               none
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DESCRIPTION

27       This  function is obsolete.  Do not use it.  See NOTES.  If you want to
28       read input without terminal echoing enabled, see the description of the
29       ECHO flag in termios(3).
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31       The  getpass() function opens /dev/tty (the controlling terminal of the
32       process), outputs the string prompt, turns off echoing, reads one  line
33       (the  "password"),  restores  the  terminal  state  and closes /dev/tty
34       again.
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RETURN VALUE

37       The function getpass() returns a pointer to a static buffer  containing
38       (the  first  PASS_MAX  bytes of) the password without the trailing new‐
39       line, terminated by a null byte ('\0').  This buffer may be overwritten
40       by  a  following call.  On error, the terminal state is restored, errno
41       is set to indicate the error, and NULL is returned.
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ERRORS

44       ENXIO  The process does not have a controlling terminal.
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FILES

47       /dev/tty
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ATTRIBUTES

50       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
51       tributes(7).
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53       ┌─────────────────────────────────────┬───────────────┬────────────────┐
54       │Interface                            │ Attribute     │ Value          │
55       ├─────────────────────────────────────┼───────────────┼────────────────┤
56       │getpass()                            │ Thread safety │ MT-Unsafe term │
57       └─────────────────────────────────────┴───────────────┴────────────────┘
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STANDARDS

60       None.
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HISTORY

63       Version  7 AT&T UNIX.  Present in SUSv2, but marked LEGACY.  Removed in
64       POSIX.1-2001.
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NOTES

67       You should use instead readpassphrase(3bsd), provided by libbsd.
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69       In the GNU C library implementation, if /dev/tty cannot be opened,  the
70       prompt is written to stderr and the password is read from stdin.  There
71       is no limit on the length of the password.  Line editing  is  not  dis‐
72       abled.
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74       According to SUSv2, the value of PASS_MAX must be defined in <limits.h>
75       in case it is smaller than 8, and can in any  case  be  obtained  using
76       sysconf(_SC_PASS_MAX).    However,   POSIX.2  withdraws  the  constants
77       PASS_MAX and _SC_PASS_MAX, and the function getpass().  The glibc  ver‐
78       sion accepts _SC_PASS_MAX and returns BUFSIZ (e.g., 8192).
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BUGS

81       The  calling  process  should  zero the password as soon as possible to
82       avoid leaving the cleartext password visible in the  process's  address
83       space.
84