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docker/usr/local/bin/wait-for-command.sh

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+#!/usr/bin/env sh
+#
+# Compare a command exit status to some given number(s) for a period of time.
+
+CMD_NAME="${0##*/}"
+CMD=""
+STATUS=0
+TIME=10
+TIME_START=0
+QUIET=0
+EXIT_STATUS=1
+
+usage() {
+  cat << EOF >&2
+Usage: ${CMD_NAME} [-c 'COMMAND']
+       ${CMD_NAME} [OPTION]... [-c 'COMMAND']
+       ${CMD_NAME} [-c 'COMMAND'] [OPTION]...
+
+${CMD_NAME} compares a command exit status to some given number(s)
+for a period of time. If comparison is successfully
+${CMD_NAME} returns 0, otherwise 1.
+
+Example: ${CMD_NAME} -c 'echo > /dev/tcp/127.0.0.1/5432'
+	 ${CMD_NAME} -s 0 57 -c 'curl 127.0.0.1:5432'
+	 ${CMD_NAME} -c 'nc -z 127.0.0.1 5432' -s 0 -t 20 -q
+
+Options:
+  -c, --command ['COMMAND']   execute a COMMAND.
+  -s, --status [NUMBER]...    target exit status of COMMAND, default 0.
+  -t, --time [NUMBER] 	      max time to wait in seconds, default 10.
+  -q, --quiet                 do not make any output, default false.
+      --help	              display this help.
+
+Notice that quotes are needed after -c/--command for multi-argument
+COMMANDs.
+
+Specifying a same OPTION more than once overrides the previews.
+So "${CMD_NAME} -c 'nothing' -c 'curl 127.0.0.1:5432'" will be
+the same as "${CMD_NAME} -c 'curl 127.0.0.1:5432'".
+It does not apply to option -q/--quiet.
+EOF
+  exit 0
+}
+
+output() {
+  if [ "${QUIET}" -ne 1 ]; then
+    printf "%s\n" "$*" 1>&2;
+  fi
+}
+
+process_command() {
+  while [ "$#" -gt 0 ]; do
+    case "$1" in
+      -c | --command)
+	# allow one shift when no arguments
+	if [ -n "$2" ]; then
+	  CMD="$2"
+          shift 1
+	fi
+	shift 1
+	;;
+      -s | --status)
+	# ensure that a number is provided
+	if ([ "$2" -eq "$2" ]) >/dev/null 2>&1; then
+	  unset STATUS
+	  # ensure that a number is provided
+	  while ([ "$2" -eq "$2" ]) >/dev/null 2>&1; do
+	    if [ -z "${STATUS}" ]; then
+	      STATUS="$2"
+	      shift 1
+            else
+	      STATUS="${STATUS} $2"
+	      shift 1
+	    fi
+          done
+	fi
+	shift 1
+	;;
+      -t | --time)
+	# ensure that a number is provided
+	if ([ "$2" -eq "$2" ]) >/dev/null 2>&1; then
+	  TIME="$2"
+	  shift 1
+	fi
+	shift 1
+	;;
+      -q | --quiet)
+	QUIET=1
+	shift 1
+	;;
+      --help)
+	usage
+	;;
+      *)
+	output "Unknown argument: $1"
+	output "Try '${CMD_NAME} --help' for more information."
+	exit "${EXIT_STATUS}"
+	;;
+    esac
+  done
+
+  if [ -z "${CMD}" ]; then
+    output "Missing command: -c, --command ['COMMAND']"
+    output "Try '${CMD_NAME} --help' for more information."
+    exit "${EXIT_STATUS}"
+  fi
+}
+
+main() {
+  message="failed"
+
+  process_command "$@"
+
+  TIME_START=$(date +%s)
+
+  while [ $(($(date +%s)-TIME_START)) -lt "${TIME}" ]; do
+
+    ($CMD) >/dev/null 2>&1 &
+    pid="$!"
+
+    # while both ps and time are running sleep 1s
+    while kill -0 "${pid}" >/dev/null 2>&1 &&
+	      [ $(($(date +%s)-TIME_START)) -lt "${TIME}" ]; do
+      sleep 1
+    done
+
+    # gets CMD status
+    kill "${pid}" >/dev/null 2>&1
+    wait "${pid}" >/dev/null 2>&1
+    cmd_exit_status="$?"
+
+    # looks for equlity in CMD exit status and one of the given status
+    for i in $STATUS; do
+      if ([ "${cmd_exit_status}" -eq "${i}" ]) >/dev/null 2>&1; then
+        message="finished successfully"
+	EXIT_STATUS=0
+	break 2
+      fi
+    done
+
+  done
+
+  output "${CMD_NAME} ${message} after $(($(date +%s)-TIME_START)) second(s)."
+  output "cmd:                 ${CMD}"
+  output "target exit status:  ${STATUS}"
+  output "exited status:       ${cmd_exit_status}"
+
+  exit "${EXIT_STATUS}"
+}
+
+main "$@"