read(2) [v7 man page]

READ(2) 							System Calls Manual							   READ(2)

NAME

       read - read from file

SYNOPSIS

       read(fildes, buffer, nbytes)
       char *buffer;

DESCRIPTION

       A  file	descriptor is a word returned from a successful open, creat, dup, or pipe call.  Buffer is the location of nbytes contiguous bytes
       into which the input will be placed.  It is not guaranteed that all nbytes bytes will be read; for example if the file refers  to  a  type-
       writer at most one line will be returned.  In any event the number of characters read is returned.

       If the returned value is 0, then end-of-file has been reached.

SEE ALSO

       open(2), creat(2), dup(2), pipe(2)

DIAGNOSTICS

       As  mentioned,  0  is  returned	when the end of the file has been reached.  If the read was otherwise unsuccessful the return value is -1.
       Many conditions can generate an error: physical I/O errors, bad buffer address, preposterous nbytes, file descriptor not that of  an  input
       file.

ASSEMBLER

       (read = 3.)
       (file descriptor in r0)
       sys read; buffer; nbytes
       (byte count in r0)

																	   READ(2)

READ(2) 							System Calls Manual							   READ(2)

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 referenced 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 guarantees to read the num-
       ber 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 variable 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).

4th Berkeley Distribution					   May 23, 1986 							   READ(2)