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authorPádraig Brady <P@draigBrady.com>2013-11-07 12:32:29 +0000
committerPádraig Brady <P@draigBrady.com>2013-11-08 13:39:35 +0000
commit90181a5926e96f34b5ffff21b81a2874a846ff6f (patch)
tree6cdda1ab6f90c873542c11de9a6d1b9dab667242
parentc2eaef2f57153a22b6dc075b1adc9fde1a4eb7bd (diff)
downloadcoreutils-90181a5926e96f34b5ffff21b81a2874a846ff6f.tar.xz
shred: avoid data write pass with --size=0
* src/shred.c (dopass): Exit early to avoid redundant heap allocation, and more importantly avoiding a file sync when we're writting no data, as this can have side effects. Also with --verbose, this avoids printing of "pass status" which could be confusing as to whether data was actually written. * tests/misc/shred-passes.sh: Ensure the status for data passes are not written when not doing any data writes.
-rw-r--r--src/shred.c4
-rwxr-xr-xtests/misc/shred-passes.sh14
2 files changed, 17 insertions, 1 deletions
diff --git a/src/shred.c b/src/shred.c
index 6ff8322c9..95a255a5b 100644
--- a/src/shred.c
+++ b/src/shred.c
@@ -378,6 +378,10 @@ dopass (int fd, char const *qname, off_t *sizep, int type,
size_t soff; /* Offset into buffer for next write */
ssize_t ssize; /* Return value from write */
+ /* Do nothing for --size=0 or regular empty files with --exact. */
+ if (size == 0)
+ return 0;
+
/* Fill pattern buffer. Aligning it to a page so we can do direct I/O. */
size_t page_size = getpagesize ();
#define PERIODIC_OUTPUT_SIZE (60 * 1024)
diff --git a/tests/misc/shred-passes.sh b/tests/misc/shred-passes.sh
index cfdd68e98..938683bce 100755
--- a/tests/misc/shred-passes.sh
+++ b/tests/misc/shred-passes.sh
@@ -31,9 +31,21 @@ shred: f: removing
shred: f: renamed to 0
shred: f: removed" > exp || framework_failure_
-
shred -v -u f 2>out || fail=1
compare exp out || fail=1
+# Likewise but with --exact to bypass the
+# data passes for the zero length file
+touch f || framework_failure_
+echo "\
+shred: f: removing
+shred: f: renamed to 0
+shred: f: removed" > exp || framework_failure_
+
+shred -x -v -u f 2>out || fail=1
+
+compare exp out || fail=1
+
+
Exit $fail