verbose(l) BEGEMOT Library verbose(l)NAMEverb - print verbose messages
SYNOPSIS
# include <begemot.h>
void verb(u_int opt, u_int level, const char *fmt, ...);
void verbc(u_int opt, u_int level, const char *fmt, ...);
void verbn(u_int opt, u_int level, const char *fmt, ...);
void vverb(u_int opt, u_int level, const char *fmt, va_list ap);
void vverbc(u_int opt, u_int level, const char *fmt, va_list ap);
void vverbn(u_int opt, u_int level, const char *fmt, va_list ap);
u_int verb_level(u_int opt);
void verb_option(char * optarg);
void verb_update(FILE * fp);
void verb_opts(verb_option_t * opts);
DESCRIPTION
The verb family of functions may be used to print debug and other
information from programs in a uniform way. They can be used in simple
programs, as well as in large programs.
The functions employ the concept of so-called verbose facilities and
levels. A facility (or option) usually represents one sub-system or
sub-function of a given program, whereas the verbose level controls the
amount of information to be printed for each facility. In simple pro‐
grams one facility (the default one) may be sufficient, whereas in com‐
plex programs it is often desirable to enable/disable debugging print‐
out in different parts of the program independent of each other.
Facilities are defined by providing a definition of an array of
verb_option_t's. This array consists of structures, the first field of
which is an ASCII string for the facility name. So the definition
verb_option_t verbopts[] = {
{ "lexer" },
{ "parser" },
{ "gen" },
{ NULL }
};
could be used to define the facilities for a compiler. The array must
be terminated with a NULL entry. If your program consists of more than
one source file, you may also want to provide symbolic definitions of
the facilities in a header file (for only one source file, you don't
need an extra header):
enum {
V_LEXER,
V_PARSER,
V_GEN
};
The option array is made known to the library by calling verb_opts. If
verb_opts is not called, the default definition from the library, con‐
taining the facility "verbose" is used, which is sufficient for simple
programs. A symbolic definition of V_DFTL is provided in this case for
the facility.
The verbose level is usually set through command line arguments. You
should aquire the habit of using the same option for verbosity in all
your programs. A convention could be to use the 'v' or 'd'. The argu‐
ment of this option should be passed to verb_option. The argument may
take one of two forms: a facility name or facility=value, where value
is an integer. In the first case, the level of the verbose facility is
incremented by one, in the second case it is set to the given value.
The facility "all" is always defined (and you can't override this defi‐
nition) to mean: change all facilities. So the string all=2 will set
all verbose levels to 2.
For simple programs with only one verbose facility, you can use your
option without an argument and call verb_option("all") instead.
Verbose levels can also be changed from a file by calling verb_update
with an open file pointer. This is useful for long-running complex pro‐
grams, where you may want to change the verbose level dynamically. In
this case you could catch a signal, open a file with a fixed name in
the signal handler and pass the file to verb_update.
To actually print something the functions verb, verbn or verbc or their
va_list equivalents are used. These functions differ in the appearance
of the output: verb prints the standard prefix (see panic(l)), the mes‐
sage and appends a newline. verbn does not append the newline and
verbc only prints the message without prefix and newline. The output is
sent to the standard error file descriptor.
To obtain the current verbose level for a given facility you may call
verb_level.
ENVIRONMENT
BEGEMOT_ERR
Overrides the prefix format mode.
SEE ALSOpanic(l),
AUTHOR
Harti Brandt
BEGEMOT 17 Mar 1998 verbose(l)
