Currently, we use "ls ... | sort -R | head -n1" (or tail) to choose a
random file in a directory.It sorts the files with "ls", sort it randomly
and pick the first line, which wastes the "ls" sort.
Also, using "sort -R | head -n1" is inefficient. For example, in a
directory with 1000000 files, it takes more than 15 seconds to pick a file.
$ time bash -c "ls -U | sort -R | head -n 1 >/dev/null"
bash -c "ls -U | sort -R | head -n 1 >/dev/null" 15.38s user 0.14s system 99% cpu 15.536 total
$ time bash -c "ls -U | shuf -n 1 >/dev/null"
bash -c "ls -U | shuf -n 1 >/dev/null" 0.30s user 0.12s system 138% cpu 0.306 total
So, we should just use "ls -U" and "shuf -n 1" to choose a random file.
Introduce _random_file() helper to do it properly.
Signed-off-by: Naohiro Aota <naohiro.aota@xxxxxxx>
---
common/rc | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/common/rc b/common/rc
index 5c4429ed0425..4d414955f6d9 100644
--- a/common/rc
+++ b/common/rc
@@ -5224,6 +5224,13 @@ _soak_loop_running() {
return 0
}
+# Return a random file in a directory. A directory is *not* followed
+# recursively.
+_random_file() {
+ local basedir=$1
+ echo "$basedir/$(ls -U $basedir | shuf -n 1)"
+}
+
init_rc
################################################################################
--
2.41.0
