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FMTMSG(3) | Linux Programmer's Manual | FMTMSG(3) |
NAME¶
fmtmsg - print formatted error messagesSYNOPSIS¶
#include <fmtmsg.h>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 written 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 MM_NULLMC (0L) does not specify any output, so nothing is printed. The dummy severity value NO_SEV (0) says that no severity is supplied. The values MM_NULLLBL, MM_NULLTXT, MM_NULLACT, MM_NULLTAG are synonyms for ((char *) 0), the empty string, and MM_NULLSEV is a synonym for NO_SEV.The classification argument¶
The classification argument is the sum of values describing 4 types of information.- MM_PRINT
- Output to stderr.
- MM_CONSOLE
- Output to the system console.
- MM_PRINT | MM_CONSOLE
- Output to both.
- MM_HARD
- A hardware error occurred.
- MM_FIRM
- A firmware error occurred.
- MM_SOFT
- A software error occurred.
- MM_APPL
- It is detected by an application.
- MM_UTIL
- It is detected by a utility.
- MM_OPSYS
- It is detected by the operating system.
- MM_RECOVER
- It is a recoverable error.
- MM_NRECOV
- It is a nonrecoverable error.
The severity argument¶
The severity argument can take one of the following values:- MM_NOSEV
- No severity is printed.
- MM_HALT
- This value is printed as HALT.
- MM_ERROR
- This value is printed as ERROR.
- MM_WARNING
- This value is printed as WARNING.
- MM_INFO
- This value is printed as INFO.
RETURN VALUE¶
The function can return 4 values:- MM_OK
- Everything went smooth.
- MM_NOTOK
- Complete failure.
- MM_NOMSG
- Error writing to stderr.
- MM_NOCON
- 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 message corresponding to these keywords is printed. Valid keywords are "label", "severity", "text", "action" and "tag". The environment variable SEV_LEVEL can be used to introduce new severity levels. By default, only the five severity levels described above are available. Any other numeric value would make fmtmsg() print nothing. If the user puts SEV_LEVEL with a format likeSEV_LEVEL=[description[:description[:...]]]
severity-keyword,level,printstring
VERSIONS¶
fmtmsg() is provided in glibc since version 2.1.CONFORMING TO¶
The functions fmtmsg() and addseverity(3), and environment variables MSGVERB and SEV_LEVEL 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 <stdio.h> #include <stdlib.h> #include <fmtmsg.h> int main(void) { long class = MM_PRINT | MM_SOFT | MM_OPSYS | MM_RECOVER; int err; err = fmtmsg(class, "util-linux:mount", MM_ERROR, "unknown mount option", "See mount(8).", "util-linux:mount:017"); switch (err) { case MM_OK: break; case MM_NOTOK: printf("Nothing printed\n"); break; case MM_NOMSG: printf("Nothing printed to stderr\n"); break; case MM_NOCON: printf("No console output\n"); break; default: printf("Unknown error from fmtmsg()\n"); } exit(EXIT_SUCCESS); }The output should be:
util-linux:mount: ERROR: unknown mount option TO FIX: See mount(8). util-linux:mount:017and after
MSGVERB=text:action; export MSGVERBthe output becomes:
unknown mount option TO FIX: See mount(8).
SEE ALSO¶
addseverity(3), perror(3)COLOPHON¶
This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.2008-06-14 |