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Changes to m4/doc/m4.texinfo,v [branch-1_4]
From: |
Eric Blake |
Subject: |
Changes to m4/doc/m4.texinfo,v [branch-1_4] |
Date: |
Mon, 11 Sep 2006 13:17:21 +0000 |
CVSROOT: /sources/m4
Module name: m4
Branch: branch-1_4
Changes by: Eric Blake <ericb> 06/09/11 13:17:21
Index: doc/m4.texinfo
===================================================================
RCS file: /sources/m4/m4/doc/m4.texinfo,v
retrieving revision 1.1.1.1.2.74
retrieving revision 1.1.1.1.2.75
diff -u -b -r1.1.1.1.2.74 -r1.1.1.1.2.75
--- doc/m4.texinfo 7 Sep 2006 22:48:15 -0000 1.1.1.1.2.74
+++ doc/m4.texinfo 11 Sep 2006 13:17:20 -0000 1.1.1.1.2.75
@@ -4093,7 +4093,7 @@
are not read by @code{m4}. @xref{Esyscmd}, if you need to process the
command output.
-Prior to executing the command, @code{m4} flushes its output buffers.
+Prior to executing the command, @code{m4} flushes its buffers.
The default standard input, output and error of @var{shell-command} are
the same as those of @code{m4}.
@@ -4119,7 +4119,11 @@
using standard input (either by specifying no files, or by passing
@samp{-} as a file name on the command line, @pxref{Invoking m4}), and
also invoking subcommands via @code{syscmd} or @code{esyscmd} that
-consume data from standard input.
+consume data from standard input. When standard input is a seekable
+file, the subprocess will pick up with the next character not yet
+processed by @code{m4}; when it is a pipe or other non-seekable file,
+there is no guarantee how much data will already be buffered by
address@hidden and thus unavailable to the child.
@ignore
@comment If the user types the example below with stdin being an
@@ -4148,7 +4152,7 @@
Expands to the standard output of the shell command
@var{shell-command}.
-Prior to executing the command, @code{m4} flushes its output buffers.
+Prior to executing the command, @code{m4} flushes its buffers.
The default standard input and error output of @var{shell-command} are
the same as those of @code{m4}. The error output of @var{shell-command}
is not a part of the expansion: it will appear along with the error
@@ -4168,6 +4172,9 @@
Note how the expansion of @code{esyscmd} keeps the trailing newline of
the command, as well as using the newline that appeared after the macro.
+Just as with @code{syscmd}, care must be exercised when sharing standard
+input between @code{m4} and the child process of @code{esyscmd}.
+
@node Sysval
@section Exit status
@@ -4452,6 +4459,11 @@
error, such as a write error on standard out, the exit status will be
non-zero even if @code{m4exit} requested zero.
+If standard input is seekable, then the file will be positioned at the
+next unread character. If it is a pipe or other non-seekable file,
+then there are no guarantees how much data @code{m4} might have read
+into buffers, and thus discarded.
+
@node Frozen files
@chapter Fast loading of frozen state
- Changes to m4/doc/m4.texinfo,v [branch-1_4], Eric Blake, 2006/09/04
- Changes to m4/doc/m4.texinfo,v [branch-1_4], Eric Blake, 2006/09/04
- Changes to m4/doc/m4.texinfo,v [branch-1_4], Eric Blake, 2006/09/05
- Changes to m4/doc/m4.texinfo,v [branch-1_4], Eric Blake, 2006/09/07
- Changes to m4/doc/m4.texinfo,v [branch-1_4],
Eric Blake <=
- Changes to m4/doc/m4.texinfo,v [branch-1_4], Eric Blake, 2006/09/14
- Changes to m4/doc/m4.texinfo,v [branch-1_4], Eric Blake, 2006/09/19
- Changes to m4/doc/m4.texinfo,v [branch-1_4], Eric Blake, 2006/09/21
- Changes to m4/doc/m4.texinfo,v [branch-1_4], Eric Blake, 2006/09/21