errno Technical Information errno External integer for return of error status extern int errno; errno is an external integer that COHERENT links into every program. COHERENT sets errno to the negative value of any error status returned by COHERENT to the functions that perform COHERENT system calls. Mathematical functions use errno to indicate classifications of errors on return. errno is defined within the header file er- rno.h. Because not every function uses errno, it should be polled only in connection with those functions that document its use and the meaning of the various status values. For the names of the error codes (as defined in errno.h, their value, and the message returned by the function perror, see errno.h. ***** Example ***** For an example of using errno in a mathematics program, see the entry for acos. ***** See Also ***** errno.h, mathematics library, perror(), signal(), technical in- formation COHERENT Lexicon Page 1