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STRERROR(3)	       FreeBSD Library Functions Manual		   STRERROR(3)

     perror, strerror, strerror_r, sys_errlist,	sys_nerr -- system error mes-

     Standard C	Library	(libc, -lc)

     #include <stdio.h>

     perror(const char *string);

     extern const char * const sys_errlist[];
     extern const int sys_nerr;

     #include <string.h>

     char *
     strerror(int errnum);

     strerror_r(int errnum, char *strerrbuf, size_t buflen);

     The strerror(), strerror_r() and perror() functions look up the error
     message string corresponding to an	error number.

     The strerror() function accepts an	error number argument errnum and
     returns a pointer to the corresponding message string.

     The strerror_r() function renders the same	result into strerrbuf for a
     maximum of	buflen characters and returns 0	upon success.

     The perror() function finds the error message corresponding to the	cur-
     rent value	of the global variable errno (intro(2))	and writes it, fol-
     lowed by a	newline, to the	standard error file descriptor.	 If the	argu-
     ment string is non-NULL and does not point	to the null character, this
     string is prepended to the	message	string and separated from it by	a
     colon and space (``: ''); otherwise, only the error message string	is

     If	the error number is not	recognized, these functions return an error
     message string containing ``Unknown error:	'' followed by the error num-
     ber in decimal.  The strerror() and strerror_r() functions	return EINVAL
     as	a warning.  Error numbers recognized by	this implementation fall in
     the range 0 < errnum < sys_nerr.  The number 0 is also recognized,
     although applications that	take advantage of this are likely to use
     unspecified values	of errno.

     If	insufficient storage is	provided in strerrbuf (as specified in buflen)
     to	contain	the error string, strerror_r() returns ERANGE and strerrbuf
     will contain an error message that	has been truncated and NUL terminated
     to	fit the	length specified by buflen.

     The message strings can be	accessed directly using	the external array
     sys_errlist.  The external	value sys_nerr contains	a count	of the mes-
     sages in sys_errlist.  The	use of these variables is deprecated;
     strerror()	or strerror_r()	should be used instead.

     intro(2), err(3), psignal(3)

     The perror() and strerror() functions conform to ISO/IEC 9899:1999
     (``ISO C99'').  The strerror_r() function conforms	to IEEE	Std
     1003.1-2001 (``POSIX.1'').

     The strerror() and	perror() functions first appeared in 4.4BSD.  The
     strerror_r() function was implemented in FreeBSD 4.4 by Wes Peters

     The strerror() function returns its result	in a static buffer which will
     be	overwritten by subsequent calls.

     The return	type for strerror() is missing a type-qualifier; it should
     actually be const char *.

     Programs that use the deprecated sys_errlist variable often fail to com-
     pile because they declare it inconsistently.

FreeBSD	11.0			 April 5, 2011			  FreeBSD 11.0


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