Mercurial > ecos-v2_0-branch

annotate packages/net/tcpip/current/doc/read.html @ 97:ced4577552cd ecos-sw-2000-06-06

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Merge from eCos master repository on 2000-06-06-08:44:00-BST
author jlarmour
date Tue, 06 Jun 2000 08:39:36 +0000
parents
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
97
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
1 <html>
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
2 <body>
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
3 <pre>
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
4 NAME
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
5 read - read from a file descriptor
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
6
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
7 SYNOPSIS
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
8 ssize_t read(int fd, void *buf, size_t count);
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
9
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
10 DESCRIPTION
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
11 read() attempts to read up to count bytes from file
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
12 descriptor fd into the buffer starting at buf.
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
13
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
14 If count is zero, read() returns zero and has no other
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
15 results.
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
16
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
17
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
18 RETURN VALUE
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
19 On success, the number of bytes read is returned (zero
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
20 indicates end of file), and the file position is advanced
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
21 by this number. It is not an error if this number is
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
22 smaller than the number of bytes requested; this may hap-
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
23 pen for example because fewer bytes are actually available
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
24 right now (maybe because we were close to end-of-file, or
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
25 because we are reading from a pipe, or from a terminal),
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
26 or because read() was interrupted by a signal. On error,
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
27 -1 is returned, and errno is set appropriately. In this
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
28 case it is left unspecified whether the file position (if
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
29 any) changes.
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
30
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
31 ERRORS
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
32 EINTR The call was interrupted by a signal before any
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
33 data was read.
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
34
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
35 EAGAIN Non-blocking I/O has been selected using O_NON-
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
36 BLOCK and no data was immediately available for
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
37 reading.
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
38
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
39 EIO I/O error. This will happen for example when the
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
40 process is in a background process group, tries to
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
41 read from its controlling tty, and either it is
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
42 ignoring or blocking SIGTTIN or its process group
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
43 is orphaned. It may also occur when there is a
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
44 low-level I/O error while reading from a disk or
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
45 tape.
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
46
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
47 EISDIR fd refers to a directory.
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
48
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
49 EBADF fd is not a valid file descriptor or is not open
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
50 for reading.
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
51
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
52 EINVAL fd is attached to an object which is unsuitable
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
53 for reading.
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
54
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
55 Other errors may occur, depending on the object connected
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
56 to fd. POSIX allows a read that is interrupted after
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
57 reading some data to return -1 (with errno set to EINTR)
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
58 or to return the number of bytes already read.
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
59 </pre>
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
60 </body>
ced4577552cd Merge from eCos master repository on 2000-06-06-08:44:00-BST
jlarmour
parents:
diff changeset
61 </html>