mirror of https://github.com/mkerrisk/man-pages
150 lines
3.9 KiB
Groff
150 lines
3.9 KiB
Groff
.\" Copyright (c) 2000 Andries Brouwer (aeb@cwi.nl)
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.\"
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.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
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.\" This is free documentation; you can redistribute it and/or
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.\" modify it under the terms of the GNU General Public License as
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.\" published by the Free Software Foundation; either version 2 of
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.\" the License, or (at your option) any later version.
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.\"
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.\" The GNU General Public License's references to "object code"
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.\" and "executables" are to be interpreted as the output of any
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.\" document formatting or typesetting system, including
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.\" intermediate and printed output.
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.\"
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.\" This manual is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public
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.\" License along with this manual; if not, see
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.\" <http://www.gnu.org/licenses/>.
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.\" %%%LICENSE_END
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.\"
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.TH GETPASS 3 2010-09-20 "Linux" "Linux Programmer's Manual"
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.SH NAME
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getpass \- get a password
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.SH SYNOPSIS
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.B #include <unistd.h>
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.sp
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.BI "char *getpass( const char *" prompt );
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.BR getpass ():
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.ad l
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.RS 4
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.PD 0
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.TP 4
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Since glibc 2.2.2:
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.nf
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_BSD_SOURCE ||
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(_XOPEN_SOURCE\ >=\ 500 ||
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_XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED) &&
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!(_POSIX_C_SOURCE\ >=\ 200112L || _XOPEN_SOURCE\ >=\ 600)
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.TP 4
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.fi
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Before glibc 2.2.2: none
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.PD
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.RE
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.ad b
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.SH DESCRIPTION
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This function is obsolete.
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Do not use it.
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.PP
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The
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.BR getpass ()
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function opens
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.I /dev/tty
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(the controlling terminal of the process), outputs the string
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.IR prompt ,
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turns off echoing, reads one line (the "password"),
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restores the terminal state and closes
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.I /dev/tty
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again.
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.SH RETURN VALUE
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The function
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.BR getpass ()
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returns a pointer to a static buffer containing (the first
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.B PASS_MAX
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bytes of) the password without the trailing
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newline, terminated by a null byte (\(aq\\0\(aq).
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This buffer may be overwritten by a following call.
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On error, the terminal state is restored,
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.I errno
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is set appropriately, and NULL is returned.
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.SH ERRORS
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The function may fail if
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.TP
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.B ENXIO
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The process does not have a controlling terminal.
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.SH FILES
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.I /dev/tty
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.\" .SH HISTORY
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.\" A
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.\" .BR getpass ()
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.\" function appeared in Version 7 AT&T UNIX.
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.SH CONFORMING TO
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Present in SUSv2, but marked LEGACY.
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Removed in POSIX.1-2001.
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.SH NOTES
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For libc4 and libc5, the prompt is not written to
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.I /dev/tty
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but to
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.IR stderr .
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Moreover, if
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.I /dev/tty
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cannot be opened, the password is read from
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.IR stdin .
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The static buffer has length 128 so that only the first 127
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bytes of the password are returned.
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While reading the password, signal generation
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.RB ( SIGINT ,
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.BR SIGQUIT ,
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.BR SIGSTOP ,
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.BR SIGTSTP )
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is disabled and the corresponding characters
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(usually control-C, control-\e, control-Z and control-Y)
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are transmitted as part of the password.
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Since libc 5.4.19 also line editing is disabled, so that also
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backspace and the like will be seen as part of the password.
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.PP
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For glibc2, if
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.I /dev/tty
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cannot be opened, the prompt is written to
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.I stderr
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and the password is read from
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.IR stdin .
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There is no limit on the length of the password.
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Line editing is not disabled.
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.PP
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According to the SUSv2, the value of
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.B PASS_MAX
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must be defined in
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.I <limits.h>
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in case it is smaller than 8, and can in any case be obtained using
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.IR sysconf(_SC_PASS_MAX) .
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However, POSIX.2 withdraws the constants
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.B PASS_MAX
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and
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.BR _SC_PASS_MAX ,
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and the function
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.BR getpass ().
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Libc4 and libc5 have never supported
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.B PASS_MAX
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or
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.BR _SC_PASS_MAX .
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Glibc2 accepts
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.B _SC_PASS_MAX
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and returns
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.B BUFSIZ
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(e.g., 8192).
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.SH BUGS
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The calling process should zero the password as soon as possible to avoid
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leaving the cleartext password visible in the process's address space.
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.SH SEE ALSO
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.BR crypt (3)
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