Add a helper script to retry failed commands

scripts/retry_command.sh

@@ -0,0 +1,73 @@
+#!/bin/sh
+
+set -e
+
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# Copyright (C) 2022-2022  kcgen <kcgen@users.noreply.github.com>
+
+usage()
+{
+    printf "%s\n" "\
+    Usage: ATTEMPTS COMMAND [[ARG1] ARG2 ...]
+    Where:
+        ATTEMPTS  : Retry the COMMAND up to this many times.
+        COMMAND   : The executable or command to run.
+        ARG(s)    : One or more arguments for the COMMAND.
+
+    Note: Place COMMAND or ARG(s) inside single or double
+          quotes if they contain spaces.
+    "
+}
+
+# Setup the error handler
+error_code=1
+fail() {
+  if [ "$error_code" -ne 0 ]; then
+    echo "$1" >&2
+  fi
+  exit "$error_code"
+}
+
+# Check number of arguments
+if [ "$#" -lt 2 ]; then
+  usage
+  fail "Please provide both the number of ATTEMPTS and COMMAND to run."
+fi
+
+# Setup our current and total number of attempts
+attempt=1
+attempts="$1"
+shift
+case "$attempts" in
+    ''|*[!0-9]*) usage; fail "$attempts is invalid, please provide a number 1 or greater"  ;;
+esac
+if [ "$attempts" -lt 1 ]; then
+  usage
+  fail "$attempts cannot be a negative number, please provide a number 1 or greater"
+fi
+
+while true; do
+  # reset the error code
+  error_code=0
+
+  # Launch and capture the error code on failure
+  $* || error_code=$?
+
+  # Quit if it passed
+  if [ "$error_code" -eq 0 ]; then
+    break
+  fi
+
+  # Inform the user
+  echo -n "\"$*\" quit with error-code $error_code on attempt $attempt of $attempts, " >&2
+
+  # Maybe loop again or bail out
+  if [ "$attempt" -lt "$attempts" ]; then
+    attempt=$((attempt+1))
+    sleep 1
+    echo "retrying ...\n" >&2
+  else
+    fail "quitting.\n"
+  fi
+done