errno(3p) - phpMan

ERRNO(P)                                                              ERRNO(P)



NAME
       errno - error return value

SYNOPSIS
       #include <errno.h>

DESCRIPTION
       The lvalue errno is used by many functions to return error values.

       Many  functions provide an error number in errno, which has type int and is defined
       in <errno.h>. The value of errno shall be defined only after a call to  a  function
       for  which  it  is  explicitly stated to be set and until it is changed by the next
       function call or if the application assigns it a value. The value of  errno  should
       only  be  examined  when  it is indicated to be valid by a function’s return value.
       Applications shall obtain the definition of errno by the inclusion of <errno.h>. No
       function in this volume of IEEE Std 1003.1-2001 shall set errno to 0.

       It  is unspecified whether errno is a macro or an identifier declared with external
       linkage. If a macro definition is suppressed in order to access an  actual  object,
       or  a program defines an identifier with the name errno, the behavior is undefined.

       The symbolic values stored in errno are documented in the ERRORS  sections  on  all
       relevant pages.

RETURN VALUE
       None.

ERRORS
       None.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       Previously  both  POSIX  and  X/Open documents were more restrictive than the ISO C
       standard in that they required errno to be defined as an external variable, whereas
       the  ISO C standard required only that errno be defined as a modifiable lvalue with
       type int.

       An application that needs to examine the value of  errno  to  determine  the  error
       should  set  it  to  0  before a function call, then inspect it before a subsequent
       function call.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Error Numbers , the Base Definitions volume of IEEE Std 1003.1-2001, <errno.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std
       1003.1,  2003  Edition,  Standard  for Information Technology -- Portable Operating
       System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C)
       2001-2003  by  the  Institute  of Electrical and Electronics Engineers, Inc and The
       Open Group. In the event of any discrepancy between this version and  the  original
       IEEE  and The Open Group Standard, the original IEEE and The Open Group Standard is
       the  referee  document.  The  original  Standard  can   be   obtained   online   at
       http://www.opengroup.org/unix/online.html .



POSIX                                2003                             ERRNO(P)

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