NAME
fmtmsg - print formatted error messages SYNOPSIS
#include
int fmtmsg(long classification, const char *label, int severity, const char *text, const char *action, const char *tag); DESCRIPTION This function displays a message described by its arguments on the device(s) specified in the classification argument. For messages writ‐ ten to stderr, the format depends on the MSGVERB environment variable. The label argument identifies the source of the message. The string must consist of two colon separated parts where the first part has not more than 10 and the second part not more than 14 characters. The text argument describes the condition of the error. The action argument describes possible steps to recover from the error. If it is printed, it is prefixed by "TO FIX: ". The tag argument is a reference to the online documentation where more information can be found. It should contain the label value and a unique identification number. Dummy arguments Each of the arguments can have a dummy value. The dummy classification value MMNULLMC (0L) does not specify any output, so nothing is printed. The dummy severity value NOSEV (0) says that no severity is supplied. The values MMNULLLBL, MMNULLTXT, MMNULLACT, MMNULLTAG are synonyms for ((char *) 0), the empty string, and MMNULLSEV is a synonym for NOSEV. The classification argument The classification argument is the sum of values describing 4 types of information. The first value defines the output channel. MMPRINT Output to stderr. MMCONSOLE Output to the system console. MMPRINT | MMCONSOLE Output to both. The second value is the source of the error: MMHARD A hardware error occurred. MMFIRM A firmware error occurred. MMSOFT A software error occurred. The third value encodes the detector of the problem: MMAPPL It is detected by an application. MMUTIL It is detected by a utility. MMOPSYS It is detected by the operating system. The fourth value shows the severity of the incident: MMRECOVER It is a recoverable error. MMNRECOV It is a nonrecoverable error. The severity argument The severity argument can take one of the following values: MMNOSEV No severity is printed. MMHALT This value is printed as HALT. MMERROR This value is printed as ERROR. MMWARNING This value is printed as WARNING. MMINFO This value is printed as INFO. The numeric values are between 0 and 4. Using addseverity(3) or the environment variable SEVLEVEL you can add more levels and strings to print. RETURN VALUE The function can return 4 values: MMOK Everything went smooth. MMNOTOK Complete failure. MMNOMSG Error writing to stderr. MMNOCON Error writing to the console. ENVIRONMENT The environment variable MSGVERB ("message verbosity") can be used to suppress parts of the output to stderr. (It does not influence output to the console.) When this variable is defined, is non-NULL, and is a
colon-separated list of valid keywords, then only the parts of the mes‐ sage corresponding to these keywords is printed. Valid keywords are "label", "severity", "text", "action" and "tag". The environment variable SEVLEVEL can be used to introduce new sever‐ ity levels. By default, only the five severity levels described above are available. Any other numeric value would make fmtmsg() print noth‐ ing. If the user puts SEVLEVEL with a format like SEVLEVEL=[description[:description[:...]]] in the environment of the process before the first call to fmtmsg(), where each description is of the form
severity-keyword,level,printstring then fmtmsg() will also accept the indicated values for the level (in
addition to the standard levels 0-4), and use the indicated printstring when such a level occurs.
The severity-keyword part is not used by fmtmsg() but it has to be present. The level part is a string representation of a number. The numeric value must be a number greater than 4. This value must be used in the severity argument of fmtmsg() to select this class. It is not possible to overwrite any of the predefined classes. The printstring is the string printed when a message of this class is processed by fmtmsg(). VERSIONS fmtmsg() is provided in glibc since version 2.1. ATTRIBUTES For an explanation of the terms used in this section, see attributes(7). ┌──────────┬───────────────┬─────────────────────────┐ │Interface │ Attribute │ Value │ ├──────────┼───────────────┼─────────────────────────┤
│fmtmsg() │ Thread safety │ glibc >= 2.16: MT-Safe │
│ │ │ glibc < 2.16: MT-Unsafe │ └──────────┴───────────────┴─────────────────────────┘ Before glibc 2.16, the fmtmsg() function uses a static variable that is
not protected, so it is not thread-safe. Since glibc 2.16, the fmtmsg() function uses a lock to protect the
static variable, so it is thread-safe. CONFORMING TO The functions fmtmsg() and addseverity(3), and environment variables MSGVERB and SEVLEVEL come from System V. The function fmtmsg() and
the environment variable MSGVERB are described in POSIX.1-2001. NOTES System V and UnixWare man pages tell us that these functions have been replaced by "pfmt() and addsev()" or by "pfmt(), vpfmt(), lfmt(), and vlfmt()", and will be removed later. EXAMPLE
#include
#include
#include
int main(void) { long class = MMPRINT | MMSOFT | MMOPSYS | MMRECOVER; int err; err = fmtmsg(class, "util-linux:mount", MMERROR, "unknown mount option", "See mount(8).",
"util-linux:mount:017"); switch (err) { case MMOK: break; case MMNOTOK: printf("Nothing printed\n"); break; case MMNOMSG: printf("Nothing printed to stderr\n"); break; case MMNOCON: printf("No console output\n"); break; default: printf("Unknown error from fmtmsg()\n"); } exit(EXITSUCCESS); } The output should be:
util-linux:mount: ERROR: unknown mount option
TO FIX: See mount(8). util-linux:mount:017 and after MSGVERB=text:action; export MSGVERB the output becomes: unknown mount option TO FIX: See mount(8). SEE ALSO addseverity(3), perror(3) COLOPHON
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2013-06-21 FMTMSG(3)