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Header file <errno.h> defines several macros,
all relating to the reporting of error conditions.
The macros are
EDOM ERANGEwhich expand to integral constant expressions with distinct nonzero values, suitable for use in
#if preprocessing
directives; and
errnowhich expands to a modifiable lvalue that has type
int, the value of which is set to a positive error number by
several library functions.
The value of errno is zero at program startup, but
is never set to zero by any library program, thus, a program that
uses errno for error checking should set it to zero
before a library function call, then inspect it before a subsequent
library function call.
The value of errno may be set to nonzero by a
library function call whether or not there is an error, provided
the use of errno is not documented in the description
of the function in the C Standard.
Implementations may specify additional macro definitions,
beginning with E and a digit or E and an
uppercase letter.
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Last modified: Thu Mar 23 13:43:10 2000