[thirdparty/man-pages.git] / man3 / getpass.3

.\" Copyright (c) 2000 Andries Brouwer (aeb@cwi.nl)
.\"
.\" This is free documentation; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License as
.\" published by the Free Software Foundation; either version 2 of
.\" the License, or (at your option) any later version.
.\"
.\" The GNU General Public License's references to "object code"
.\" and "executables" are to be interpreted as the output of any
.\" document formatting or typesetting system, including
.\" intermediate and printed output.
.\"
.\" This manual is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
.\" GNU General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public
.\" License along with this manual; if not, write to the Free
.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
.\" USA.
.\"
.TH GETPASS 3  2000-12-05 "Linux Manpage" "Linux Programmer's Manual"
.SH NAME
getpass \- get a password
.SH SYNOPSIS
.B #include <unistd.h>
.sp
.B "char *getpass( const char *" prompt );
.SH DESCRIPTION
This function is obsolete. Do not use it.
.PP
The
.BR getpass ()
function opens
.I /dev/tty
(the controlling terminal of the process), outputs the string
.IR prompt ,
turns off echoing, reads one line (the "password"),
restores the terminal state and closes
.I /dev/tty
again.
.SH "RETURN VALUE"
The function
.B getpass
returns a pointer to a static buffer containing the
(first PASS_MAX bytes of) the password without the trailing
newline, terminated by a NUL.
This buffer may be overwritten by a following call.
On error, the terminal state is restored,
.I errno
is set appropriately, and NULL is returned.
.SH ERRORS
The function may fail if
.TP
.B ENXIO
The process does not have a controlling terminal. 
.SH NOTES
For libc4 and libc5, the prompt is not written to
.I /dev/tty
but to
.IR stderr .
Moreover, if
.I /dev/tty
cannot be opened, the password is read from
.IR 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, SIGTSTOP) is disabled and the corresponding characters
(usually control-C, control-\e, 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.
.PP
For glibc2, if
.I /dev/tty
cannot be opened, the prompt is written to
.I stderr
and the password is read from
.IR stdin .
There is no limit on the length of the password.
Line editing is not disabled.
.PP
According to the SUSv2, the value of PASS_MAX must be defined in
.I <limits.h>
in case it is smaller than 8, and can in any case be obtained using
.IR sysconf(_SC_PASS_MAX) .
However, POSIX.2 withdraws the constants PASS_MAX
and _SC_PASS_MAX, and the function
.B getpass ().
Libc4 and libc5 have never supported PASS_MAX or _SC_PASS_MAX.
Glibc2 accepts _SC_PASS_MAX and returns BUFSIZ (e.g., 8192).
.SH FILES
.I /dev/tty
.SH "SEE ALSO"
.BR crypt (3)
.SH HISTORY
A
.B getpass
function appeared in Version 7 AT&T UNIX.
.SH 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.
Commit	Line	Data
fea681da MK	1	.\" Copyright (c) 2000 Andries Brouwer (aeb@cwi.nl)
	2	.\"
	3	.\" This is free documentation; you can redistribute it and/or
	4	.\" modify it under the terms of the GNU General Public License as
	5	.\" published by the Free Software Foundation; either version 2 of
	6	.\" the License, or (at your option) any later version.
	7	.\"
	8	.\" The GNU General Public License's references to "object code"
	9	.\" and "executables" are to be interpreted as the output of any
	10	.\" document formatting or typesetting system, including
	11	.\" intermediate and printed output.
	12	.\"
	13	.\" This manual is distributed in the hope that it will be useful,
	14	.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
	15	.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	16	.\" GNU General Public License for more details.
	17	.\"
	18	.\" You should have received a copy of the GNU General Public
	19	.\" License along with this manual; if not, write to the Free
	20	.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
	21	.\" USA.
	22	.\"
	23	.TH GETPASS 3 2000-12-05 "Linux Manpage" "Linux Programmer's Manual"
	24	.SH NAME
	25	getpass \- get a password
	26	.SH SYNOPSIS
	27	.B #include <unistd.h>
	28	.sp
	29	.B "char getpass( const char " prompt );
	30	.SH DESCRIPTION
	31	This function is obsolete. Do not use it.
	32	.PP
	33	The
	34	.BR getpass ()
	35	function opens
	36	.I /dev/tty
	37	(the controlling terminal of the process), outputs the string
	38	.IR prompt ,
	39	turns off echoing, reads one line (the "password"),
	40	restores the terminal state and closes
	41	.I /dev/tty
	42	again.
	43	.SH "RETURN VALUE"
	44	The function
	45	.B getpass
	46	returns a pointer to a static buffer containing the
	47	(first PASS_MAX bytes of) the password without the trailing
	48	newline, terminated by a NUL.
	49	This buffer may be overwritten by a following call.
	50	On error, the terminal state is restored,
	51	.I errno
	52	is set appropriately, and NULL is returned.
	53	.SH ERRORS
	54	The function may fail if
	55	.TP
	56	.B ENXIO
	57	The process does not have a controlling terminal.
	58	.SH NOTES
	59	For libc4 and libc5, the prompt is not written to
	60	.I /dev/tty
	61	but to
	62	.IR stderr .
	63	Moreover, if
	64	.I /dev/tty
65	cannot be opened, the password is read from
66	.IR stdin .
67	The static buffer has length 128 so that only the first 127
68	bytes of the password are returned.
69	While reading the password, signal generation (SIGINT, SIGQUIT,
70	SIGSTOP, SIGTSTOP) is disabled and the corresponding characters
71	(usually control-C, control-\e, control-Z and control-Y)
72	are transmitted as part of the password.
73	Since libc 5.4.19 also line editing is disabled, so that also
74	backspace and the like will be seen as part of the password.
75	.PP
76	For glibc2, if
77	.I /dev/tty
78	cannot be opened, the prompt is written to
79	.I stderr
80	and the password is read from
81	.IR stdin .
82	There is no limit on the length of the password.
83	Line editing is not disabled.
84	.PP
85	According to the SUSv2, the value of PASS_MAX must be defined in
86	.I <limits.h>
87	in case it is smaller than 8, and can in any case be obtained using
88	.IR sysconf(_SC_PASS_MAX) .
89	However, POSIX.2 withdraws the constants PASS_MAX
90	and _SC_PASS_MAX, and the function
91	.B getpass ().
92	Libc4 and libc5 have never supported PASS_MAX or _SC_PASS_MAX.
93	Glibc2 accepts _SC_PASS_MAX and returns BUFSIZ (e.g., 8192).
94	.SH FILES
95	.I /dev/tty
96	.SH "SEE ALSO"
97	.BR crypt (3)
98	.SH HISTORY
99	A
100	.B getpass
101	function appeared in Version 7 AT&T UNIX.
102	.SH BUGS
103	The calling process should zero the password as soon as possible to avoid
104	leaving the cleartext password visible in the process's address space.