If a file disappears after reading directory entries tree(1) treats this as a fatal error. I think the code should just ignore files which have disappeared.
Observed when running tree on a directory where temporary files are constantly created and deleted. $ while true; do tree >/dev/null || break; done in this directory will eventually fail with tree: fts_read: No such file or directory Index: Makefile =================================================================== RCS file: /cvs/ports/sysutils/tree/Makefile,v retrieving revision 1.7 diff -u -p -r1.7 Makefile --- Makefile 23 Jun 2011 22:50:29 -0000 1.7 +++ Makefile 9 Sep 2011 12:54:41 -0000 @@ -3,7 +3,7 @@ COMMENT= print ascii formatted tree of a directory structure DISTNAME= tree-0.61 -REVISION = 3 +REVISION = 4 CATEGORIES= sysutils HOMEPAGE= http://spootnik.org/tree/ Index: patches/patch-tree_c =================================================================== RCS file: /cvs/ports/sysutils/tree/patches/patch-tree_c,v retrieving revision 1.1 diff -u -p -r1.1 patch-tree_c --- patches/patch-tree_c 21 Sep 2010 19:17:31 -0000 1.1 +++ patches/patch-tree_c 9 Sep 2011 12:59:08 -0000 @@ -1,6 +1,6 @@ $OpenBSD: patch-tree_c,v 1.1 2010/09/21 19:17:31 stsp Exp $ --- tree.c.orig Wed Jun 21 20:47:54 2006 -+++ tree.c Mon Sep 20 19:59:40 2010 ++++ tree.c Fri Sep 9 14:59:04 2011 @@ -139,7 +139,7 @@ format_entry(FTSENT *entry) if (entry->fts_info == FTS_SL) { @@ -10,3 +10,14 @@ $OpenBSD: patch-tree_c,v 1.1 2010/09/21 err(1, "readlink: %s", entry->fts_path); sz += strlen(buf) + 5; if ((str = realloc(str, sz)) == NULL) +@@ -182,7 +182,9 @@ walk(char *path, int ftsoptions) + (void)printf("%s\n", path); + for (entry = fts_read(tree); entry != NULL; entry = fts_read(tree)) { + +- if (entry->fts_info == FTS_ERR || entry->fts_info == FTS_NS) ++ if (entry->fts_info == FTS_NS) ++ continue; ++ if (entry->fts_info == FTS_ERR) + errx(1, "fts_read: %s", strerror(entry->fts_errno)); + + padlen = (depth * 4) + 1;
