NetBSD/share/man/man9/kprintf.9

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.Dd January 15, 2006
.Dt KPRINTF 9
.Os
.Sh NAME
.Nm printf, snprintf, vprintf, vsnprintf, uprintf, ttyprintf, tprintf
.Nd kernel formatted output conversion
.Sh SYNOPSIS
.In sys/systm.h
.Ft void
.Fn "printf" "const char *format" "..."
.Ft void
.Fn "printf_nolog" "const char *format" "..."
.Ft int
.Fn "snprintf" "char *buf" "size_t size" "const char *format" "..."
.Ft void
.Fn "vprintf" "const char *format" "va_list ap"
.Ft int
.Fn "vsnprintf" "char *buf" "size_t size" "const char *format" "va_list ap"
.Ft void
.Fn "uprintf" "const char *format" "..."
.Ft void
.Fn "ttyprintf" "struct tty *tty" "const char *format" "..."
.In sys/tprintf.h
.Ft tpr_t
.Fn "tprintf_open" "struct proc *p"
.Ft void
.Fn "tprintf" "tpr_t tpr" "const char *format" "..."
.Ft void
.Fn "tprintf_close" "tpr_t tpr"
.Ft void
.Fn "aprint_normal" "const char *format" "..."
.Ft void
.Fn "aprint_naive" "const char *format" "..."
.Ft void
.Fn "aprint_verbose" "const char *format" "..."
.Ft void
.Fn "aprint_debug" "const char *format" "..."
.Ft void
.Fn "aprint_error" "const char *format" "..."
.Ft int
.Fn "aprint_get_error_count" "void"
.Sh DESCRIPTION
The
.Fn printf
family of functions allows the kernel to send formatted messages to various
output devices.
The functions
.Fn printf
and
.Fn vprintf
send formatted strings to the system console.
The
.Fn printf_nolog
function is identical to
.Fn printf ,
except it does not send the data to the system log.
The functions
.Fn snprintf
and
.Fn vsnprintf
write output to a string buffer.
These four functions work similarly to their user space counterparts,
and are not described in detail here.
.Pp
The functions
.Fn uprintf
and
.Fn ttyprintf
send formatted strings to the current process's controlling tty and a specific
tty, respectively.
.Pp
The
.Fn tprintf
function sends formatted strings to a process's controlling tty,
via a handle of type tpr_t.
This allows multiple write operations to the tty with a guarantee that the
tty will be valid across calls.
A handle is acquired by calling
.Fn tprintf_open
with the target process as an argument.
This handle must be closed with a matching call to
.Fn tprintf_close .
.Pp
The functions
.Fn aprint_normal ,
.Fn aprint_naive ,
.Fn aprint_verbose ,
.Fn aprint_debug ,
and
.Fn aprint_error
are intended to be used to print autoconfiguration messages, and change
their behavior based on flags in the
.Dq boothowto
variable:
.Bl -tag -width "aprint_verbose()"
.It Fn aprint_normal
Sends to the console unless
.Dv AB_QUIET
is set.
Always sends to the log.
.It Fn aprint_naive
Sends to the console only if
.Dv AB_QUIET
is set.
Never sends to the log.
.It Fn aprint_verbose
Sends to the console only if
.Dv AB_VERBOSE
is set.
Always sends to the log.
.It Fn aprint_debug
Sends to the console and the log only if
.Dv AB_DEBUG
is set.
.It Fn aprint_error
Like
.Fn aprint_normal ,
but also keeps track of the number of times called.
This allows a subsystem to report the number of errors that occurred
during a quiet or silent initialization phase.
The
.Fn aprint_get_error_count
function reports the number of errors and resets the counter to 0.
.El
.Pp
If
.Dv AB_SILENT
is set, none of the autoconfiguration message printing routines send output
to the console.
The
.Dv AB_VERBOSE
and
.Dv AB_DEBUG
flags override
.Dv AB_SILENT .
.Sh RETURN VALUES
The
.Fn snprintf
and
.Fn vsnprintf
functions return the number of characters placed in the buffer
.Fa buf .
This is different to the user-space functions of the same name.
.Pp
The
.Fn tprintf_open
function returns
.Dv NULL
if no terminal handle could be acquired.
.Sh SEE ALSO
.Xr printf 1 ,
.Xr printf 3 ,
.Xr bitmask_snprintf 9
.Sh CODE REFERENCES
.Pa sys/kern/subr_prf.c
.Sh HISTORY
The
.Fn sprintf
and
.Fn vsprintf
unsized string formatting functions are supported for compatibility only,
and are not documented here.
New code should use the size-limited
.Fn snprintf
and
.Fn vsnprintf
functions instead.
.Pp
In
.Nx 1.5
and earlier,
.Fn printf
supported more format strings than the user space
.Fn printf .
These nonstandard format strings are no longer supported.
For the functionality provided by the former
.Li %b
format string, see
.Xr bitmask_snprintf 9 .
.Pp
The
.Fn aprint_normal ,
.Fn aprint_naive ,
.Fn aprint_verbose ,
and
.Fn aprint_debug
functions first appeared in
.Bsx .
.Sh BUGS
The
.Fn uprintf
and
.Fn ttyprintf
functions should be used sparingly, if at all.
Where multiple lines of output are required to reach a process's
controlling terminal,
.Fn tprintf
is preferred.