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PERROR(3C)                           SysV                           PERROR(3C)



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

SYNOPSIS
     #include <stdio.h>
     void perror(s)
     const char *s;

     #include <string.h>

     char *strerror(errnum)
     int errnum;

     strerror_r (errnum, buffer, len)
     int errnum;
     char *buffer;
     int len;

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

DESCRIPTION
     The perror function maps the error number in errno to an error message.
     It generates a short error message on the standard error file, describing
     the error encountered by a C program during its most recent call to the
     system.  If s is not null, and does not point to the null character,
     perror prints s, followed by a colon and a blank.  The error message,
     terminated with a newline, is then printed, regardless of the value of s.
     To be of most use, s should include the name of the program that incurred
     the error.

     The error message is selected from sys_errlist, using the value of the
     external variable errno, which is set when errors occur but not cleared
     by successful calls.

     To simplify creation of variant formats, the vector of message strings
     sys_errlist is provided.  sys_nerr is the number of messages provided for
     in the table.  If errnum is less than sys_nerr, strerror returns an
     address from sys_errlist pointing to a message string without the
     newline.  Otherwise, strerror returns a pointer to the string "Unknown
     error". You should check sys_nerr because new error codes may be added to
     the system before they are added to the table.  Typically, the value
     passed to strerror should be errno.

     The contents of the error message strings are the same as those returned
     by the strerror function.

     The perror function marks the file associated with the standard error
     error stream as having been written (st_ctime st_mtime marked for update)
     at some time between its successful completion and the completion of
     fflush(3) or fclose(3) on stderr, or exit(2) or abort(2).

     The strerror function maps the error number in errnum to an error message
     string and returns a pointer thereto. The string pointed to is not
     modified by the program, but may be overwritten by a subsequent call to
     the strerror function.

     strerror_r is the reentrant version of the strerror function.

ERRORS
     If strerror or strerror_r fails, errno may be set to the following value:

     [EINVAL]
          len is less than NL_TEXTMAX as specified in limits.h.

NOTES
     More verbose, Domain/OS-specific error messages may be obtained by
     setting the environment variable APOLLO_STATUS to "true".

SEE ALSO
     <stdio.h>.