.\" Copyright (c) 1980, 1991 Regents of the University of California.
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.\" @(#)read.2 6.7 (Berkeley) 3/10/91
.Fd #include <sys/types.h>
.Fn read "int d" "char *buf" "size_t nbytes"
.Fn readv "int d" "struct iovec *iov" "int iovcnt"
of data from the object referenced by the descriptor
into the buffer pointed to by
performs the same action, but scatters the input data
buffers specified by the members of the
array: iov[0], iov[1], ..., iov[iovcnt\|\-\|1].
.Bd -literal -offset indent -compact
entry specifies the base address and length of an area
in memory where data should be placed.
will always fill an area completely before proceeding
On objects capable of seeking, the
given by the pointer associated with
the pointer is incremented by the number of bytes actually read.
Objects that are not capable of seeking always read from the current
position. The value of the pointer associated with such an
Upon successful completion,
return the number of bytes actually read and placed in the buffer.
The system guarantees to read the number of bytes requested if
the descriptor references a normal file that has that many bytes left
before the end-of-file, but in no other case.
number of bytes actually read is returned. Upon reading end-of-file,
Otherwise, a -1 is returned and the global variable
is set to indicate the error.
is not a valid file or socket descriptor open for reading.
points outside the allocated address space.
An I/O error occurred while reading from the file system.
A read from a slow device was interrupted before
any data arrived by the delivery of a signal.
The pointer associated with
The file was marked for non-blocking I/O,
and no data were ready to be read.
may return one of the following errors:
was less than or equal to 0, or greater than 16.
array overflowed a 32-bit integer.
points outside the process's allocated address space.
is expected to conform to IEEE Std 1003.1-1988