STRERROR(3)						   BSD Library Functions Manual 					       STRERROR(3)

NAME

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

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <stdio.h>

     void
     perror(const char *string);

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

     #include <string.h>

     char *
     strerror(int errnum);

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

DESCRIPTION

     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 current value of the global variable errno (intro(2)) and writes it, fol-
     lowed by a newline, to the standard error file descriptor.  If the argument 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
     printed.

     If the error number is not recognized, these functions return an error message string containing ``Unknown error: '' followed by the error
     number 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.

SEE ALSO

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

STANDARDS

     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'').

HISTORY

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

BUGS

     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 compile because they declare it inconsistently.

BSD
								   April 5, 2011							       BSD