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getpass(3) [linux man page]

GETPASS(3)						     Linux Programmer's Manual							GETPASS(3)

NAME
getpass - get a password SYNOPSIS
#include <unistd.h> char *getpass( const char *prompt); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): getpass(): Since glibc 2.2.2: _BSD_SOURCE || (_XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) && !(_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600) Before glibc 2.2.2: none DESCRIPTION
This function is obsolete. Do not use it. The getpass() function opens /dev/tty (the controlling terminal of the process), outputs the string prompt, turns off echoing, reads one line (the "password"), restores the terminal state and closes /dev/tty 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 null byte (''). This buffer may be overwritten by a following call. On error, the terminal state is restored, errno is set appropriately, and NULL is returned. ERRORS
The function may fail if ENXIO The process does not have a controlling terminal. FILES
/dev/tty CONFORMING TO
Present in SUSv2, but marked LEGACY. Removed in POSIX.1-2001. NOTES
For libc4 and libc5, the prompt is not written to /dev/tty but to stderr. Moreover, if /dev/tty cannot be opened, the password is read 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 generation (SIGINT, SIGQUIT, SIGSTOP, SIGTSTP) 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 /dev/tty cannot be opened, the prompt is written to stderr and the password is read 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 <limits.h> in case it is smaller than 8, and can in 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). 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. SEE ALSO
crypt(3) COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 2010-09-20 GETPASS(3)

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getpass(3C)						   Standard C Library Functions 					       getpass(3C)

NAME
getpass, getpassphrase - read a string of characters without echo SYNOPSIS
#include <stdlib.h> char *getpass(const char *prompt); char *getpassphrase(const char *prompt); XPG4, SUS, SUSv2 #include <unistd.h> char *getpass(const char *prompt); DESCRIPTION
The getpass() function opens the process's controlling terminal, writes to that device the null-terminated string prompt, disables echoing, reads a string of characters up to the next newline character or EOF, restores the terminal state and closes the terminal. The getpassphrase() function is identical to getpass(), except that it reads and returns a string of up to 257 characters in length. RETURN VALUES
Upon successful completion, getpass() returns a pointer to a null-terminated string of at most 9 bytes that were read from the terminal device. If an error is encountered, the terminal state is restored and a null pointer is returned. ERRORS
The getpass() and getpassphrase() functions may fail if: EINTR The function was interrupted by a signal. EIO The process is a member of a background process attempting to read from its controlling terminal, the process is ignoring or blocking the SIGTTIN signal or the process group is orphaned. EMFILE OPEN_MAX file descriptors are currently open in the calling process. ENFILE The maximum allowable number of files is currently open in the system. ENXIO The process does not have a controlling terminal. USAGE
The return value points to static data whose content may be overwritten by each call. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |getpass() is Standard. | +-----------------------------+-----------------------------+ |MT-Level |Unsafe | +-----------------------------+-----------------------------+ SEE ALSO
attributes(5), standards(5) SunOS 5.11 2 Sep 2003 getpass(3C)

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