From: Martin v. Löwis <martin@v.loewis.de>
Date: Sat, 18 Oct 2003 09:38:01 +0000 (+0000)
Subject: Patch #809535: Mention behaviour of seek on text files. Backported to 2.3.
X-Git-Tag: v2.4a1~1422
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=849a972f35a6740c4784c80a8271af9f5592d7b6;p=python

Patch #809535: Mention behaviour of seek on text files. Backported to 2.3.
---

diff --git a/Doc/lib/libstdtypes.tex b/Doc/lib/libstdtypes.tex
index 62f16446c5..531e385e9d 100644
--- a/Doc/lib/libstdtypes.tex
+++ b/Doc/lib/libstdtypes.tex
@@ -1337,7 +1337,12 @@ flush the read-ahead buffer.
   \method{seek()} operations will be undone at the next write.  If the
   file is only opened for writing in append mode (mode \code{'a'}),
   this method is essentially a no-op, but it remains useful for files
-  opened in append mode with reading enabled (mode \code{'a+'}).
+  opened in append mode with reading enabled (mode \code{'a+'}).  If the
+  file is opened in text mode (mode \code{'t'}), only offsets returned
+  by \method{tell()} are legal.  Use of other offsets causes undefined
+  behavior.
+
+  Note that not all file objects are seekable.
 \end{methoddesc}
 
 \begin{methoddesc}[file]{tell}{}
diff --git a/Objects/fileobject.c b/Objects/fileobject.c
index 6f90fb9e84..ff66117b11 100644
--- a/Objects/fileobject.c
+++ b/Objects/fileobject.c
@@ -1613,7 +1613,9 @@ PyDoc_STRVAR(seek_doc,
 "0 (offset from start of file, offset should be >= 0); other values are 1\n"
 "(move relative to current position, positive or negative), and 2 (move\n"
 "relative to end of file, usually negative, although many platforms allow\n"
-"seeking beyond the end of a file).\n"
+"seeking beyond the end of a file).  If the file is opened in text mode,\n"
+"only offsets returned by tell() are legal.  Use of other offsets causes\n"
+"undefined behavior."
 "\n"
 "Note that not all file objects are seekable.");