fmemopen.3: Expand discussion of "current position" for fmemopen() stream

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/man3/fmemopen.3 b/man3/fmemopen.3
index 6b56cb4e8a..dc5136bda0 100644
--- a/man3/fmemopen.3
+++ b/man3/fmemopen.3
@@ -79,8 +79,18 @@ The buffer contents are truncated
 Append; open the stream for reading and writing,
 with the file initial position set to the first null byte.
 .PP
+The stream maintains the notion of a current position,
+the location where the next I/O operation will be performed.
+The current position is implicitly updated by I/O operations.
+It can be explicitly updated using
+.BR fseek (3),
+and determined using
+.BR ftell (3).
 In all modes other than append,
 the initial position is set to the start of the buffer.
+In append mode, if no null byte is found within the buffer,
+then the initial position is
+.IR size+1 .
 .PP
 If
 .I buf