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.Dd September 1, 1998 .Dt KPRINTF 9 .Os .Sh NAME .Nm printf, snprintf, vprintf, vsnprintf, uprintf, ttyprintf, tprintf .Nd kernel formatted output conversion .Sh SYNOPSIS .Fd #include <sys/systm.h> .Ft void .Fn "printf" "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" "..." .Fd #include <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" .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 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.
p The functions .Fn uprintf and .Fn ttyprintf send formatted strings to the current process's controlling tty and a specific tty, respectively.
p 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 . .Sh RETURN VALUES The .Fn snprintf and .Fn vsnprintf functions return the number of characters placed in the buffer .Fa buf . .Sh SEE ALSO .Xr printf 1 , .Xr printf 3 , .Xr bitmask_snprintf 9 .Sh CODE REFERENCES
a 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.
p 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 . .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.