pfmt(3C) pfmt(3C)
NAME
pfmt, vpfmt - display error message in standard format
SYNOPSIS
#include <pfmt.h>
int pfmt(FILE *stream, long flags, char *format, . . . /* args */);
#include <stdarg.h>
#include <pfmt.h>
int vpfmt(FILE *stream, long flags, char *format, va_list ap);
DESCRIPTION
pfmt
pfmt uses a format string for printf style formatting of args.
The output is displayed on stream. pfmt encapsulates the
output in the standard error message format.
If the printf format string is to be retrieved from a message
database, the format argument must have the following
structure:
[[catalog]:[msgnum]:]defmsg.
defmsg can only appear alone if flags include MM_NOGET.
catalog indicates the message database that contains the
localized version of the format string. catalog must be
limited to 14 characters. These characters must be selected
from a set of all characters values, excluding \0 (null) and
the ASCII codes for / (slash) and : (colon).
msgnum must be a positive number that indicates the index of
the string into the message database.
If catalog does not exist in the locale (specified by the last
call to setlocale using the LC_ALL or LC_MESSAGES categories),
or if the message number is out of bounds, pfmt attempts to
retrieve the message from the C locale. If this second
retrieval fails, pfmt uses the defmsg part of the format
argument.
If catalog is omitted, pfmt attempts to retrieve the string
from the default catalog specified by the last call to setcat.
In this case, the format argument has the following structure:
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pfmt(3C) pfmt(3C)
msgnum:defmsg.
pfmt outputs
Message not found!! . . .
as the format string if:
catalog is not a valid catalog name as defined above
no catalog is specified (either explicitly or via
setcat)
msgnum is not a positive number,
no message could be retrieved and defmsg was omitted
The flags determine the type of output (that is, whether the
format should be interpreted as is or encapsulated in the
standard message format), and the access to message catalogs
to retrieve a localized version of format.
The flags are composed of several groups, and can take the
following values (one from each group):
Output format control
MM_NOSTD do not use the standard message format,
interpret format as a printf format. Only
catalog access control flags should be
specified if MM_NOSTD is used; all other
flags will be ignored.
MM_STD output using the standard message format
(default, value 0).
Catalog access control
MM_NOGET do not retrieve a localized version of
format. In this case, only the defmsg part
of the format is specified.
MM_GET retrieve a localized version of format,
from the catalog, using msgnum as the index
and defmsg as the default message (default,
value 0).
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pfmt(3C) pfmt(3C)
Severity (standard message format only)
MM_HALT generates a localized version of HALT.
MM_ERROR generates a localized version of ERROR
(default, value 0).
MM_WARNING generates a localized version of WARNING.
MM_INFO generates a localized version of INFO.
Additional severities can be defined.
Add-on severities can be defined with
number-string pairs with numeric values
from the range [5-255], using addsev(3C).
The numeric value ORed with other flags
will generate the specified severity.
If the severity is not defined, pfmt uses
the string SEV=N where N is replaced by 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).
Action
MM_ACTION specifies an action message. Any severity
value is superseded and replaced by a
localized version of TO FIX.
Standard Error Message Format
pfmt displays error messages in the following format:
label: severity: text
If no label was defined by a call to setlabel, the message is
displayed in the format:
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pfmt(3C) pfmt(3C)
severity: text
If pfmt is called twice to display an error message and a
helpful action or recovery message, the output can look like:
label: severity: text
label: TO FIX: text
vpfmt
vpfmt is the same as pfmt except that instead of being called
with a variable number of arguments, it is called with an
argument list as defined by the stdarg.h header file.
The stdarg.h header file defines the type va_list and a set of
macros for advancing through a list of arguments whose number
and types may vary. The argument ap to vpfmt is of type
va_list. This argument is used with the stdarg.h header file
macros va_start, va_arg and va_end [see va_start, va_arg, and
va_end in stdarg(5)]. The USAGE sections below show their
use.
The macro va_alist is used as the parameter list in a function
definition as in the function called error in the example
below. The macro
va_start(ap, )
where ap is of type va_list, must be called before any attempt
to traverse and access unnamed arguments. Calls to
va_arg(ap, atype)
traverse the argument list. Each execution of va_arg expands
to an expression with the value and type of the next argument
in the list ap, which is the same object initialized by
va_start. The argument atype is the type that the returned
argument is expected to be.
The
va_end(ap)
macro must be invoked when all desired arguments have been
accessed. [The argument list in ap can be traversed again if
va_start is called again after va_end.] In the example below,
va_arg is executed first to retrieve the format string passed
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to error. The remaining error arguments, arg1, arg2, . . .,
are given to vpfmt in the argument ap.
Return Values
On success, pfmt and vpfmt return the number of bytes
transmitted. On failure, they return a negative value:
Errors
-1 write error to stream
USAGE
pfmt Example 1
setlabel("UX:test");
pfmt(stderr, MM_ERROR, "test:2:Cannot open file: %s\n",
strerror(errno));
displays the message:
UX:test: ERROR: Cannot open file: No such file or directory
pfmt Example 2
setlabel("UX:test");
setcat("test");
pfmt(stderr, MM_ERROR, ":10:Syntax error\n");
pfmt(stderr, MM_ACTION, ":55:Usage ...\n");
displays the message
UX:test: ERROR: Syntax error
UX:test: TO FIX: Usage ...
vpfmt Example
The following demonstrates how vpfmt could be used to write an
error routine:
#include <pfmt.h>
#include <stdarg.h>
. . .
/*
* error should be called like
* error(format, arg1, ...);
*/
void error(const char *format, ...)
{
va_list ap;
va_start(ap, );
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(void) vpfmt(stderr, MM_ERROR, format, ap);
va_end(ap);
(void) abort();
}
REFERENCES
addsev(3C), environ(5), fprintf(3S), gettxt(3C), lfmt(3C),
pfmt(1), setcat(3C), setlabel(3C), setlocale(3C), stdarg(5)
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