[PATCH] redir: detect larger pipe sizes under Linux

[Eric Wong <e@80x24.org>]

Not sure if it's worth it, 4K is a lot for heredoc

	SCRIPT=${SCRIPT-heredoc.sh}
	(
		echo 'cat >/dev/null <<EOF'
		awk </dev/null 'END{for(i=0;i<6000;i++) print 012345789}'
		echo 'EOF'
	) >"$SCRIPT"
---
 src/redir.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/src/redir.c b/src/redir.c
index f96a76b..8a65951 100644
--- a/src/redir.c
+++ b/src/redir.c
@@ -285,6 +285,29 @@ err:
 	sh_error("%d: %s", f, strerror(err));
 }
 
+static size_t
+pipesize(int fd, int want)
+{
+#if defined(F_GETPIPE_SZ) && defined(F_SETPIPE_SZ)
+	static int default_size;
+
+	if (!default_size) {
+		int sz = fcntl(fd, F_GETPIPE_SZ, &sz);
+
+		default_size = sz > 0 ? sz : PIPESIZE;
+	}
+	if (want > default_size) {
+		if (fcntl(fd, F_SETPIPE_SZ, &want) < 0)
+			return default_size;
+
+		return want;
+	}
+
+	return default_size;
+#else
+	return PIPESIZE;
+#endif
+}
 
 /*
  * Handle here documents.  Normally we fork off a process to write the
@@ -309,7 +332,7 @@ openhere(union node *redir)
 	}
 
 	len = strlen(p);
-	if (len <= PIPESIZE) {
+	if (len <= pipesize(pip[0], len)) {
 		xwrite(pip[1], p, len);
 		goto out;
 	}
-- 
EW