1 .\" Copyright (c) 2000 Andries Brouwer (aeb@cwi.nl)
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24 .TH GETPASS 3 2021-03-22 "Linux" "Linux Programmer's Manual"
26 getpass \- get a password
29 .B #include <unistd.h>
31 .BI "char *getpass(const char *" prompt );
35 Feature Test Macro Requirements for glibc (see
36 .BR feature_test_macros (7)):
42 _XOPEN_SOURCE && ! (_POSIX_C_SOURCE >= 200112L)
43 || /* Glibc since 2.19: */ _DEFAULT_SOURCE
44 || /* Glibc <= 2.19: */ _BSD_SOURCE
49 This function is obsolete.
51 If you want to read input without terminal echoing enabled,
52 see the description of the
61 (the controlling terminal of the process), outputs the string
63 turns off echoing, reads one line (the "password"),
64 restores the terminal state and closes
70 returns a pointer to a static buffer containing (the first
72 bytes of) the password without the trailing
73 newline, terminated by a null byte (\(aq\e0\(aq).
74 This buffer may be overwritten by a following call.
75 On error, the terminal state is restored,
77 is set to indicate the error, and NULL is returned.
79 The function may fail if
82 The process does not have a controlling terminal.
88 .\" function appeared in Version 7 AT&T UNIX.
90 For an explanation of the terms used in this section, see
98 Interface Attribute Value
101 T} Thread safety MT-Unsafe term
107 Present in SUSv2, but marked LEGACY.
108 Removed in POSIX.1-2001.
110 .\" For libc4 and libc5, the prompt is not written to
116 .\" cannot be opened, the password is read from
118 .\" The static buffer has length 128 so that only the first 127
119 .\" bytes of the password are returned.
120 .\" While reading the password, signal generation
125 .\" is disabled and the corresponding characters
126 .\" (usually control-C, control-\e, control-Z and control-Y)
127 .\" are transmitted as part of the password.
128 .\" Since libc 5.4.19 also line editing is disabled, so that also
129 .\" backspace and the like will be seen as part of the password.
131 In the GNU C library implementation, if
133 cannot be opened, the prompt is written to
135 and the password is read from
137 There is no limit on the length of the password.
138 Line editing is not disabled.
140 According to SUSv2, the value of
144 in case it is smaller than 8, and can in any case be obtained using
145 .IR sysconf(_SC_PASS_MAX) .
146 However, POSIX.2 withdraws the constants
152 .\" Libc4 and libc5 have never supported
155 .\" .BR _SC_PASS_MAX .
156 The glibc version accepts
162 The calling process should zero the password as soon as possible to avoid
163 leaving the cleartext password visible in the process's address space.