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

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

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <stdio.h>

     void
     perror(const char *s);

     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 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 s 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 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.

     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), 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
     For unknown error numbers, the strerror() function will return its result
     in a static buffer which may 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.

BSD                            October 12, 2004                            BSD