GETPASS(3) Linux Programmer's Manual GETPASS(3)
NAME
getpass - get a password
SYNOPSIS
#include <unistd.h>
char *getpass( const char * prompt );
DESCRIPTION
This function is obsolete. Do not use it.
The getpass() function opens /dev/tty(1,4) (the controlling terminal of the
process), outputs the string(3,n) prompt, turns off echoing, reads one line
(the "password"), restores the terminal state and closes /dev/tty(1,4)
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 new-
line, terminated by a NUL. This buffer may be overwritten by a follow-
ing call. On error(8,n), the terminal state is restored, errno is set(7,n,1 builtins)
appropriately, and NULL is returned.
ERRORS
The function may fail if(3,n)
ENXIO The process does not have a controlling terminal.
NOTES
For libc4 and libc5, the prompt is not written to /dev/tty(1,4) but to
stderr. Moreover, if(3,n) /dev/tty(1,4) cannot be opened, the password is read(2,n,1 builtins)
from stdin. The static buffer has length 128 so that only the first
127 bytes of the password are returned. While reading the password,
signal(2,7) generation (SIGINT, SIGQUIT, SIGSTOP, SIGTSTOP) is disabled and
the corresponding characters (usually control-C, control-\, 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.
For glibc2, if(3,n) /dev/tty(1,4) cannot be opened, the prompt is written to
stderr and the password is read(2,n,1 builtins) from stdin. There is no limit on the
length of the password. Line editing is not disabled.
According to the SUSv2, the value of PASS_MAX must be defined in(1,8) <lim-
its.h> in(1,8) case it is smaller than 8, and can in(1,8) 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 (). Libc4 and
libc5 have never supported PASS_MAX or _SC_PASS_MAX. Glibc2 accepts
_SC_PASS_MAX and returns BUFSIZ (e.g., 8192).
FILES
/dev/tty(1,4)
SEE ALSO
crypt(3)
HISTORY
A getpass function appeared in(1,8) Version 7 AT&T UNIX.
BUGS
The calling process should zero the password as soon as possible to
avoid leaving the cleartext password visible in(1,8) the process's address
space.
Linux Manpage 2000-12-05 GETPASS(3)