path: root/lib/libc/gen/fmtmsg.3

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.Dd April 11, 2011
.Dt FMTMSG 3
.Os
.Sh NAME
.Nm fmtmsg
.Nd format and display a message
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In fmtmsg.h
.Ft int
.Fn fmtmsg "long classification" "const char *label" "int severity" "const char *text" "const char *action" "const char *tag"
.Sh DESCRIPTION
The
.Fn fmtmsg
function can be used to display messages in the specified format.
Messages may be written either to standard error, to the console, or both.
.Pp
A formatted message consists of up to five components specified in
.Fa label ,
.Fa severity ,
.Fa text ,
.Fa action
and
.Fa tag .
Further information such as the origin of the message, the recoverability
from the condition causing the message and where to display the message
is specified in
.Fa classification .
.Ss Classification
The
.Fa classification
argument consists of a major classification and several sub-classifications.
It has no effect on the content of the message displayed.
With the exception of the display sub-classification, only a single identifier
may be specified for each (sub-)classification.
The following classifications
are available:
.Bl -tag -width "XXX"
.It Em Major classifications
The source of the condition.
Available identifiers are:
.Dv MM_HARD
(hardware),
.Dv MM_SOFT
(software), and
.Dv MM_FIRM
(firmware).
.It Em Message source sub-classifications
The type of software detecting the condition.
Available identifiers are:
.Dv MM_APPL
(application),
.Dv MM_UTIL
(utility), and
.Dv MM_OPSYS
(operating system).
.It Em Display sub-classifications
The displays the formatted messages is to be written to.
Available identifiers are:
.Dv MM_PRINT
(standard error stream) and
.Dv MM_CONSOLE
(system console).
.It Em Status sub-classifications
The capability of the calling software to recover from the condition.
Available identifiers are:
.Dv MM_RECOVER
(recoverable) and
.Dv MM_NRECOV
(non-recoverable).
.El
.Pp
If no
.Fa classification
is to be supplied,
.Dv MM_NULLMC
must be specified.
.Ss Label
The
.Fa label
argument identifies the source of the message.
It consists of two fields separated by a colon (:).
The first field is up to 10 characters, the second is up to 14 characters.
.Pp
If no
.Fa label
is to be supplied,
.Dv MM_NULLLBL
must be specified.
.Ss Severity
The seriousness of the condition causing the message.
The following
.Fa severity
levels are available:
.Bl -tag -width MM_WARNING -offset indent
.It Dv MM_HALT
The software has encountered a severe fault and is halting.
.It Dv MM_ERROR
The software has encountered a fault.
.It Dv MM_WARNING
The software has encountered an unusual non-fault condition.
.It Dv MM_INFO
The software informs about a non-error condition.
.El
.Pp
If no
.Fa severity
level is to be supplied,
.Dv MM_NOSEV
must be specified.
.Ss Text
The description of the condition the software encountered.
The character
string is not limited to a specific size.
.Pp
If no
.Fa text
is to be supplied,
.Dv MM_NOTXT
must be specified.
.Ss Action
The first step to be taken to recover from the condition the software
encountered; it will be preceded by the prefix
.Dq TO FIX: .
The character string is not limited to a specific size.
.Pp
If no
.Fa action
is to be supplied,
.Dv MM_NOACT
must be specified.
.Ss Tag
The on-line documentation which provides further information about the
condition and the message, such as
.Dq Xr fmtmsg 3 .
The character string is not limited to a specific size.
.Pp
If no
.Fa tag
is to be supplied,
.Dv MM_NOTAG
must be specified.
.Pp
Further effect on the formatting of the message as displayed on the
standard error stream (but not on the system console!) may be taken by
setting the
.Ev MSGVERB
environment variable, which selects the subset of message components
to be printed.
It consists of a colon-separated list of the optional keywords
.Fa label ,
.Fa severity ,
.Fa text ,
.Fa action ,
and
.Fa tag ,
which correspond to the arguments to
.Fn fmtmsg
with the same names.
If
.Ev MSGVERB
is either not set or malformed (containing empty or unknown keywords),
its content is ignored an all message components will be selected.
.Pp
Note that displaying a message on the system console may fail due to
inappropriate privileges or a non-permissive file mode of the console device.
.Sh RETURN VALUES
The
.Fn fmtmsg
function returns one of the following values:
.Bl -tag -width MM_NOTOKXXX
.It Dv MM_OK
The function succeeded.
.It Dv MM_NOTOK
The function failed completely.
.It Dv MM_NOMSG
The function was unable to generate a message on standard error,
but otherwise succeeded.
.It Dv MM_NOCOM
The function was unable to generate a message on the console,
but otherwise succeeded.
.El
.Sh SEE ALSO
.Xr printf 3 ,
.Xr syslog 3
.Sh STANDARDS
The
.Fn fmtmsg
function conforms to
.St -xsh5 .