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).