define a retry_command function in Makefile

Makefile

# retry command with max retries and sleep time
# Notes: No Spaces between commas
# usage: $(call retry_command, command[,max_retries[,sleep_time]])
# example1: $(call retry_command, command -v jx,3,1s)
# example2: $(call retry_command, command -v jx)
# example3: $(call retry_command, command -v jx,3)
define retry_command
	@max_retries=$(or $(2),10); \
	sleep_time=$(or $(3),5s); \
	retries=0; \
	while ! $(1); do \
		retries=$$((retries + 1)); \
		if [[ $$retries -ge $$max_retries ]]; then \
			echo "Failed to execute command after $$max_retries attempts."; \
			exit 1; \
		fi;	\
		echo "Retrying ($$retries/$$max_retries)..."; \
		sleep $$sleep_time; \
	done
endef

x:
	$(call retry_command, command -v jx)

xx:
	$(call retry_command, x,3,1s)

This code defines a makefile function named retry_command that attempts to execute a command until it succeeds or reaches a maximum number of retries. This function takes three parameters:

1. $(1): The command to be executed.
2. $(2): The maximum number of retries, defaulting to 10.
3. $(3): The wait time between each retry, defaulting to 5 seconds.

If the command still fails after reaching the maximum number of retries, the function will output an error message and exit.

Then, this code defines two targets x and xx that call the retry_command function to execute the command -v jx and x commands, respectively. For the xx target, the maximum number of retries is set to 3 and the wait time between each retry is 1 second.

This is a very practical function that can handle situations where command execution fails due to unstable network or other reasons. By retrying, it increases the chance of successful command execution.

这段代码定义了一个名为 retry_command 的 makefile 函数，它用于尝试执行一个命令直到成功，或者达到最大重试次数。这个函数接受三个参数：

1. $(1): 要执行的命令。
2. $(2): 最大重试次数，默认为10次。
3. $(3): 每次重试之间的等待时间，默认为5秒。

如果在达到最大重试次数后命令仍然失败，函数将输出一条错误消息并退出。

然后，这段代码定义了两个目标 x 和 xx，它们分别调用 retry_command 函数来执行 command -v jx 和 x 命令。对于 xx 目标，最大重试次数被设置为3次，每次重试之间的等待时间为1秒。

这是一个非常实用的函数，可以用于处理网络不稳定或者其他原因导致的命令执行失败的情况。通过重试，可以增加命令成功执行的机会。