Go to main content

man pages section 3: Basic Library Functions

Exit Print View

Updated: Wednesday, July 27, 2022



lfmt - display error message in standard format and pass to logging and monitoring services


#include <pfmt.h>

int lfmt(FILE *stream, long flags, char *format, ... /* arg*/);


The lfmt() function retrieves a format string from a locale-specific message database (unless MM_NOGET is specified) and uses it for printf(3C) style formatting of args. The output is displayed on stream. If stream is NULL no output is displayed.

The lfmt() function encapsulates the output in the standard error message format (unless MM_NOSTD is specified, in which case the output is like that of printf(). It forwards its output to the logging and monitoring facility, even if stream is NULL. Optionally, lfmt() displays the output on the console with a date and time stamp.

If the printf() format string is to be retrieved from a message database, the format argument must have the following structure:


If MM_NOGET is specified, only the <defmsg> field must be specified.

The <catalog> field indicates the message database that contains the localized version of the format string. This field is limited to 14 characters selected from a set of all characters values, excluding the null character (\0) and the ASCII codes for slash (/) and colon (:).

The <msgnum> field is a positive number that indicates the index of the string into the message database.

If the catalog does not exist in the locale (specified by the last call to setlocale(3C) using the LC_ALL or LC_MESSAGES categories), or if the message number is out of bound, lfmt() will attempt to retrieve the message from the C locale. If this second retrieval fails, lfmt() uses the <defmsg> field of the format argument.

If <catalog> is omitted, lfmt() will attempt to retrieve the string from the default catalog specified by the last call to setcat(3C). In this case, the format argument has the following structure:


The lfmt() function will output the message

Message not found!!\n

as the format string if <catalog> is not a valid catalog name, if no catalog is specified (either explicitly or with setcat()), if <msgnum> is not a valid number, or if no message could be retrieved from the message databases and <defmsg> was omitted.

The flags argument determines the type of output (whether the format should be interpreted as it is or be encapsulated in the standard message format) and the access to message catalogs to retrieve a localized version of format.

The flags argument is composed of several groups, and can take the following values (one from each group):

Output format control

Do not use the standard message format but interpret format as a printf() format. Only catalog access control flags, console display control and logging information should be specified if MM_NOSTD is used; all other flags will be ignored.


Output using the standard message format (default value is 0).

Catalog access control

Do not retrieve a localized version of format. In this case, only the <defmsg> field of format is specified.


Retrieve a localized version of format from <catalog>, using <msgid> as the index and <defmsg> as the default message (default value is 0).

Severity (standard message format only)

Generate a localized version of HALT, but do not halt the machine.


Generate a localized version of ERROR (default value is 0).


Generate a localized version of WARNING.


Generate a localized version of INFO.

Additional severities can be defined with the addsev(3C) function, using number-string pairs with numeric values in the range [5-255]. The specified severity is formed by the bitwise OR operation of the numeric value and other flags arguments.

If the severity is not defined, lfmt() uses the string SEV=N where N is the integer severity value passed in flags.

Multiple severities passed in flags will not be detected as an error. Any combination of severities will be summed and the numeric value will cause the display of either a severity string (if defined) or the string SEV=N (if undefined).


Specify an action message. Any severity value is superseded and replaced by a localized version of TO FIX.

Console display control

Display the message to the console in addition to the specified stream.


Do not display the message to the console in addition to the specified stream (default value is 0).

Logging information
Major classification

Identify the source of the condition. Identifiers are: MM_HARD (hardware), MM_SOFT (software), and MM_FIRM (firmware).

Message source subclassification

Identify the type of software in which the problem is spotted. Identifiers are: MM_APPL (application), MM_UTIL (utility), and MM_OPSYS (operating system).


The lfmt() function displays error messages in the following format:

label: severity: text

If no label was defined by a call to setlabel(3C), the message is displayed in the format:

severity: text

If lfmt() is called twice to display an error message and a helpful action or recovery message, the output may appear as follows:

label: severity: text
label: TO FIX: text

Return Values

Upon successful completion, lfmt() returns the number of bytes transmitted. Otherwise, it returns a negative value:


Write the error to stream.


Cannot log and/or display at console.


Since lfmt() uses gettxt(3C), it is recommended that lfmt() not be used.


Example 1 The following example
     "test:2:Cannot open file: %s\n", strerror(errno));

displays the message to stderr and to the console and makes it available for logging:

UX:test: ERROR: Cannot open file: No such file or directory
Example 2 The following example
lfmt(stderr, MM_INFO|MM_SOFT|MM_UTIL,
        "test:23:test facility is enabled\n");

displays the message to stderr and makes it available for logging:

UX:test: INFO: test facility enabled


See attributes(7) for descriptions of the following attributes:


See Also

addsev(3C), gettxt(3C), pfmt(3C), printf(3C), setcat(3C), setlabel(3C), setlocale(3C), attributes(7), environ(7)