add cros-safe-write.bash

cros-safe-write.bash

+#!/bin/bash
+# Copy stdin to a file
+
+cmd=$(basename "$0")
+usage="Usage: $cmd DST < SRC
+
+Where DST is the destination file
+
+Copy stdin to DST. Data is flushed regularly to avoid some eventual crash during cache sync.
+
+Example:
+  gunzip myimage.img.gz -c | sudo bash $cmd /dev/sda"
+
+KiB=1024
+MiB=$((1024 * $KiB))
+bs=4096
+count=$((50 * $MiB / $bs))
+
+infostep=50
+infounit=MiB
+
+cooldd() {
+  local _cooldd_out
+  local _cooldd_length=$infostep
+  [ $# = 1 ] || { echo "$usage" >&2 ; return 2 ; }
+  [ $1 != - ] || { echo "DST should not be '-'" >&2 ; return 2 ; }
+  while [ $? = 0 ] ; do
+    echo "+ copying until $_cooldd_length $infounit"
+    _cooldd_length=$(($_cooldd_length + $infostep))
+    _cooldd_out=$(dd bs=$bs count=$count of="$1" 2>&1) || { echo "$_cooldd_out" ; return 1 ; }
+    echo "$_cooldd_out"
+    ! echo "$_cooldd_out" | grep '(0 B) copied' > /dev/null
+  done
+  return 0
+}
+
+cooldd "$@"