NAME
read - read input
SYNOPSIS
#include <sys/types.h>
#include <unistd.h>
ssize_t read(int d, void *buf, size_t nbytes)
DESCRIPTION
Read attempts to read nbytes of data from the object refer-
enced by the descriptor d into the buffer pointed to by buf.
On objects capable of seeking, the read starts at a position
given by the pointer associated with d (see lseek(2)). Upon
return from read, 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 object is undefined.
Upon successful completion, read return the number of bytes
actually read and placed in the buffer. The system guaran-
tees 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.
If the returned value is 0, then end-of-file has been
reached.
RETURN VALUE
If successful, the number of bytes actually read is
returned. Otherwise, a -1 is returned and the global vari-
able errno is set to indicate the error.
ERRORS
Read will fail if one or more of the following are true:
[EBADF] D is not a valid descriptor open for reading.
[EFAULT] Buf points outside the allocated address
space.
[EIO] An I/O error occurred while reading from the
file system.
[EINTR] A read from a slow device was interrupted
before any data arrived by the delivery of a
signal.
[EAGAIN] The file was marked for non-blocking I/O, and
no data were ready to be read.
SEE ALSO
dup(2), fcntl(2), open(2), pipe(2), write(2).