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-rw-r--r--man/io_uring.736
1 files changed, 27 insertions, 9 deletions
diff --git a/man/io_uring.7 b/man/io_uring.7
index 972683b..dc76f42 100644
--- a/man/io_uring.7
+++ b/man/io_uring.7
@@ -84,17 +84,35 @@ a read operation under
.BR io_uring ,
started with the
.BR IORING_OP_READ
-operation,
-which issues the equivalent of the
+operation, issues the equivalent of the
.BR read (2)
-system call,
-would return as part of
+system call. In practice, it mixes the semantics of
+.BR pread (2)
+and
+.BR preadv2 (2)
+in that it takes an explicit offset, and supports using -1 for the offset to
+indicate that the current file position should be used instead of passing in
+an explicit offset. See the opcode documentation for more details. Given that
+io_uring is an async interface,
+.I errno
+is never used for passing back error information. Instead,
.I res
-what
-.BR read (2)
-would have returned if called directly,
-without using
-.BR io_uring .
+will contain what the equivalent system call would have returned in case
+of success, and in case of error
+.I res
+will contain
+.I -errno .
+For example, if the normal read system call would have returned -1 and set
+.I errno
+to
+.B EINVAL ,
+then
+.I res
+would contain
+.B -EINVAL .
+If the normal system call would have returned a read size of 1024, then
+.I res
+would contain 1024.
.IP \(bu
Optionally,
.BR io_uring_enter (2)