#include <lcio.h> size_t afreadh(void *ptr, size_t size, size_t count, FILE *f);
afreadh
reads up to count
items from the current record of the
stream associated with the FILE
object that f
addresses.
size
defines the size of each item, and ptr
addresses the area
into which the items will be read.
Calls to afreadh
to obtain items of type typeval
commonly have
this form:
typeval buf[count]; afreadh(buf, sizeof(typeval), count, f);
afreadh
can only be used with a binary stream. See
Augmented Standard I/O for more information.
afreadh
returns the number of items read from the record (which may be
less than the maximum).
afreadh
behaves exactly
like fread
because these files are processed as a continuous stream
of characters without record boundaries. To process a file with relative
attributes on a record-by-record basis, you must open it with afopen
and specify the "seq"
access method.
If afreadh
reads a zero-length record, it skips it and ignores it.
Use the afread0
function if you are processing a file that may
contain zero-length records.
afreadh
never reads past the end of the current record; an error occurs
if the record contains a fractional number of items.
The return value from afreadh
does not indicate whether the call was
completely successful. You can use the ferror
function to determine
whether an error occurred.
#include <lcio.h> #define NAMESIZE 30 #define ADDRSIZE 80 main() { FILE *custf; struct hdr { int custno; char type; }; struct custrec { char name[NAMESIZE]; char addr[ADDRSIZE]; }; typedef double payrec; struct hdr header; struct custrec customer; payrec payment; custf = fopen("tso:custfile", "rb"); if (!custf) exit(1); for (;;) { /* Read customer number and record type. */ afreadh(&header, sizeof(header), 1, custf); if (feof(custf) || ferror(custf)) break; if (header.type == 'C'){ /* a customer record */ /* Read rest of customer record. */ afread(&customer, sizeof(customer), 1, custf); if (feof(custf) || ferror(custf)) break; printf("Customer record %d read:n" "Name: %snAddress: %sn", header.custno, customer.name, customer.addr); } else if (header.type == 'P'){ /* a payment record */ afread(&payment, sizeof(payment), 1, custf); if (feof(custf) || ferror(custf)) break; printf("Payment record for customer %d read:n" "Amount: %.2fn", header.custno, payment); } else{ printf("Unknown record type %c, aborting.n", header.type); abort(); } } if (ferror(custf)){ puts("Aborting due to error reading file."); abort(); } fclose(custf); exit(0); }
afread
Copyright (c) 1998 SAS Institute Inc. Cary, NC, USA. All rights reserved.