manual page distributed with 4.2BSD

SCCS-vsn: lib/libc/sys/read.2 5.1

diff --git a/usr/src/lib/libc/sys/read.2 b/usr/src/lib/libc/sys/read.2
index fbf44ce..ee458bc 100644 (file)
--- a/usr/src/lib/libc/sys/read.2
+++ b/usr/src/lib/libc/sys/read.2
@@ -2,80 +2,138 @@
 .\" All rights reserved.  The Berkeley software License Agreement
 .\" specifies the terms and conditions for redistribution.
 .\"
 .\" All rights reserved.  The Berkeley software License Agreement
 .\" specifies the terms and conditions for redistribution.
 .\"

-.\"    @(#)read.2      4.1 (Berkeley) %G%
+.\"    @(#)read.2      5.1 (Berkeley) %G%

 .\"
 .\"

-.TH READ 2 
+.TH READ 2 "27 July 1983"

 .UC 4
 .SH NAME
 .UC 4
 .SH NAME

-read \- read from file
+read, readv \- read input

 .SH SYNOPSIS
 .nf
 .SH SYNOPSIS
 .nf

-.B read(fildes, buffer, nbytes)
-.B char *buffer;
+.ft B
+cc = read(d, buf, nbytes)
+int cc, d;
+char *buf;
+int nbytes;
+.PP
+.ft B
+#include <sys/types.h>
+#include <sys/uio.h>
+.PP
+.ft B
+cc = readv(d, iov, iovcnt)
+int cc, d;
+struct iovec *iov;
+int iovcnt;

 .fi
 .SH DESCRIPTION
 .fi
 .SH DESCRIPTION

-A file descriptor is a word
-returned from a successful
-.I "open, creat, dup,"
-or
-.I pipe
-call.
-.I Buffer
-is the location of
+.I Read
+attempts to read

 .I nbytes
 .I nbytes

-contiguous
-bytes into which the input will be placed.
-It is not guaranteed
-that all
-.I nbytes
-bytes will be read; for example
-if the file refers to a typewriter at most one line
-will be returned.
-In any event the number of characters read is returned.
+of data from the object referenced by the descriptor
+.I d
+into the buffer pointed to by
+.IR buf .
+.I Readv
+performs the same action, but scatters the input data
+into the 
+.I iovcnt
+buffers specified by the members of the
+.I iovec
+array: iov[0], iov[1], ..., iov[iovcnt\|\-\|1].

 .PP
 .PP

-If the returned value is 0, then
-end-of-file has been reached.
+For 
+.IR readv ,
+the 
+.I iovec
+structure is defined as

 .PP
 .PP

-Unless the reader is ignoring or holding SIGTTIN signals,
-reads from the control typewriter while not in its process group
-cause a SIGTTIN signal to be sent to the reader's process group;
-in the former case an end-of-file is returned.
+.nf
+.RS
+.DT
+struct iovec {
+       caddr_t iov_base;
+       int     iov_len;
+};
+.RE
+.fi

 .PP
 .PP

-.SH "SEE ALSO"
-open(2), creat(2), dup(2), pipe(2), vread(2)
-.SH 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
-.I nbytes,
-file descriptor not that of
-an input file.
-.SH "ASSEMBLER (PDP-11)"
-(read = 3.)
-.br
-(file descriptor in r0)
-.br
-.B sys read; buffer; nbytes
-.br
-(byte count in r0)
-.SH BUGS
-It should be possible to call
+Each 
+.I iovec
+entry specifies the base address and length of an area
+in memory where data should be placed. 
+.I Readv
+will always fill an area completely before proceeding
+to the next.
+.PP
+On objects capable of seeking, the

 .I read
 .I read

-and have it return immediately without blocking if there is no input available.
-As a single special case, this is currently done on control terminals
-when the reading process has requested SIGTINT signals when input arrives
-(see
-.IR tty (4)).
+starts at a position
+given by the pointer associated with
+.IR d ,
+see
+.IR lseek (2).
+Upon return from
+.IR read ,
+the pointer is incremented by the number of bytes actually read.
+.PP
+Objects that are not capable of seeking always read from the current
+position.  The value of the pointer associated with such a 
+object is undefined.

 .PP
 .PP

-Processes which have been orphaned by their parents
-and have been inherited by
-.IR init (8)
-never receive SIGTTIN signals.
-Instead
+Upon successful completion,

 .I read
 .I read

-returns with an end-of-file indication.
+and
+.I readv
+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 file which has that many bytes left
+before the end-of-file, but in no other cases.
+.PP
+If the returned value is 0, then
+end-of-file has been reached.
+.SH "RETURN VALUE
+If successful, the
+number of bytes actually read is returned.
+Otherwise, a \-1 is returned and the global variable
+.I errno
+is set to indicate the error.
+.SH "ERRORS
+.I Read
+and
+.I readv
+will fail if one or more of the following are true:
+.TP 15
+[EBADF]
+\fIFildes\fP is not a valid file descriptor open for reading.
+.TP 15
+[EFAULT]
+\fIBuf\fP points outside the allocated address space.
+.TP 15
+[EINTR]
+A read from a slow device was interrupted before
+any data arrived by the delivery of a signal.
+.PP
+In addition, 
+.I readv
+may return one of the following errors:
+.TP 15
+[EINVAL]
+.I Iovcnt
+was less than or equal to 0, or greater than 16.
+.TP 15
+[EINVAL]
+One of the
+.I iov_len
+values in the
+.I iov
+array was negative.
+.TP 15
+[EINVAL]
+The sum of the
+.I iov_len
+values in the
+.I iov
+array overflowed a 32-bit integer.
+.SH "SEE ALSO"
+dup(2), open(2), pipe(2), socket(2), socketpair(2)