FMTMSG(3) BSD Library Functions Manual FMTMSG(3)NAMEfmtmsg — display a detailed diagnostic message
Standard C Library (libc, -lc)
fmtmsg(long classification, const char *label, int severity,
const char *text, const char *action, const char *tag);
The fmtmsg() function displays a detailed diagnostic message, based on
the supplied arguments, to stderr and/or the system console.
The classification argument is the bitwise inclusive OR of zero or one of
the manifest constants from each of the classification groups below. The
Output classification group is an exception since both MM_PRINT and
MM_CONSOLE may be specified.
MM_PRINT Output should take place on stderr.
MM_CONSOLE Output should take place on the system console.
Source of Condition (Major)
MM_HARD The source of the condition is hardware related.
MM_SOFT The source of the condition is software related.
MM_FIRM The source of the condition is firmware related.
Source of Condition (Minor)
MM_APPL The condition was detected at the application level.
MM_UTIL The condition was detected at the utility level.
MM_OPSYS The condition was detected at the operating system
MM_RECOVER The application can recover from the condition.
MM_NRECOV The application is unable to recover from the condi‐
Alternatively, the MM_NULLMC manifest constant may be used to specify no
The label argument indicates the source of the message. It is made up of
two fields separated by a colon (‘:’). The first field can be up to 10
bytes, and the second field can be up to 14 bytes. The MM_NULLLBL mani‐
fest constant may be used to specify no label.
The severity argument identifies the importance of the condition. One of
the following manifest constants should be used for this argument.
MM_HALT The application has confronted a serious fault and is
MM_ERROR The application has detected a fault.
MM_WARNING The application has detected an unusual condition, that
could be indicative of a problem.
MM_INFO The application is providing information about a non-
MM_NOSEV No severity level supplied.
The text argument details the error condition that caused the message.
There is no limit on the size of this character string. The MM_NULLTXT
manifest constant may be used to specify no text.
The action argument details how the error-recovery process should begin.
Upon output, fmtmsg() will prefix "TO FIX:" to the beginning of the
action argument. The MM_NULLACT manifest constant may be used to specify
The tag argument should reference online documentation for the message.
This usually includes the label and a unique identifying number. An
example tag is "BSD:ls:168". The MM_NULLTAG manifest constant may be
used to specify no tag.
The fmtmsg() function returns MM_OK upon success, MM_NOMSG to indicate
output to stderr failed, MM_NOCON to indicate output to the system con‐
sole failed, or MM_NOTOK to indicate output to stderr and the system con‐
The MSGVERB (message verbosity) environment variable specifies which
arguments to fmtmsg() will be output to stderr, and in which order.
MSGVERB should be a colon (‘:’) separated list of identifiers. Valid
identifiers include: label, severity, text, action, and tag. If invalid
identifiers are specified or incorrectly separated, the default message
verbosity and ordering will be used. The default ordering is equivalent
to a MSGVERB with a value of "label:severity:text:action:tag".
fmtmsg(MM_UTIL | MM_PRINT, "BSD:ls", MM_ERROR,
"illegal option -- z", "refer to manual", "BSD:ls:001");
BSD:ls: ERROR: illegal option -- z
TO FIX: refer to manual BSD:ls:001
The same code, with MSGVERB set to "text:severity:action:tag", produces:
illegal option -- z: ERROR
TO FIX: refer to manual BSD:ls:001
SEE ALSOerr(3), exit(3), strerror(3)STANDARDS
The fmtmsg() function conforms to IEEE Std 1003.1-2001 (“POSIX.1”).
The fmtmsg() function first appeared in FreeBSD 5.0.
Specifying MM_NULLMC for the classification argument makes little sense,
since without an output specified, fmtmsg() is unable to do anything use‐
In order for fmtmsg() to output to the system console, the effective user
must have appropriate permission to write to /dev/console. This means
that on most systems fmtmsg() will return MM_NOCON unless the effective
user is root.
BSD August 5, 2002 BSD