NAME

getpass — get a password

SYNOPSIS

#include <pwd.h>
#include <unistd.h>

char *
getpass(const char *prompt);

DESCRIPTION

The getpass() function displays a prompt to, and reads in a password from, /dev/tty. If this file is not accessible, getpass() displays the prompt on the standard error output and reads from the standard input.

The password may be up to _PASSWORD_LEN (currently 128, as defined in the <pwd.h> include file) characters in length. Any additional characters and the terminating newline character are discarded.

getpass() turns off character echoing while reading the password.

The calling process should zero the password with explicit_bzero(3) as soon as possible to avoid leaving the cleartext password visible in the process's address space.

RETURN VALUES

Upon successful completion, getpass() returns a pointer to a NUL-terminated string of at most _PASSWORD_LEN characters. If an error is encountered, the terminal state is restored and a null pointer is returned.

FILES

/dev/tty

 

ERRORS

[EINTR]

The getpass() 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]

The process has already reached its limit for open file descriptors.

[ENFILE]

The system file table is full.

SEE ALSO

crypt(3), readpassphrase(3)

STANDARDS

Historically, BSD versions of getpass() have accepted a password on the standard input if /dev/tty is unavailable. This contradicts X/Open Portability Guide Issue 4, Version 2 (“XPG4.2”) but the OpenBSD implementation is conformant in all other respects. Removed from IEEE Std 1003.1-2001 (“POSIX.1”).

HISTORY

A getpass() function appeared in Version 7 AT&T UNIX.

CAVEATS

The getpass() function leaves its result in an internal static object and returns a pointer to that object. Subsequent calls to getpass() will modify the same object.