read(2) [plan9 man page]

READ(2) 							System Calls Manual							   READ(2)

NAME

       read, readn, write - read or write file

SYNOPSIS

       #include <u.h>
       #include <libc.h>

       long read(int fd, void *buf, long nbytes)

       long readn(int fd, void *buf, long nbytes)

       long write(int fd, void *buf, long nbytes)

DESCRIPTION

       Read reads nbytes bytes of data from the offset in the file associated with fd into memory at buf.  The offset is advanced by the number of
       bytes read.  It is not guaranteed that all nbytes bytes will be read; for example if the file refers to the console, at most one line  will
       be returned.  In any event the number of characters read is returned.  A return value of 0 is conventionally interpreted as end of file.

       Readn is just like read, but does successive read calls until nbytes have been read, or a read system call returns a non-positive count.

       Write  writes nbytes bytes of data starting at buf to the file associated with fd at the file offset.  The offset is advanced by the number
       of bytes written.  The number of characters actually written is returned.  It should be regarded as an error if this is	not  the  same	as
       requested.

SOURCE

       /sys/src/libc/9syscall
       /sys/src/libc/port/readn.c

SEE ALSO

       intro(2), open(2), dup(2), pipe(2)

DIAGNOSTICS

       These functions set errstr.

																	   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)