在makefile中打印时间戳 [英] Print timestamp in makefile

问题描述

我想测量make文件中每个构建项目的时间，我只是在下面尝试，为什么它不起作用?

I want to measure the time for each of build item in make file, i just try below, why does it not work?

mytest:
    $(info 'Now time is $(date --iso=seconds)')

不打印日期，仅打印

'Now time is '

.有什么问题吗?

make --version GNU Make 3.81

make --version GNU Make 3.81

推荐答案

没有名为date的make函数.如果要调用shell命令，语法为$(shell date).

There is no make function named date. If you want to invoke a shell command, the syntax is $(shell date).

在食谱中使用$(info)并不是特别优雅；该函数不会产生任何对传递给shell有用的东西.您可能只是在寻找

Using $(info) in a recipe is not particularly elegant; the function doesn't produce anything which is useful to pass to a shell. You are probably looking simply for

mytest:
    date +"Now time is +%FT%T%z"

(找不到正确记录的--iso-seconds；从此博客中获取了定义:

(Could not find --iso-seconds documented properly; grabbed the defintion from this blog: http://nixscripts.blogspot.com/2010/07/hidden-arguments-easter-egg-or-what.html)

...或可能效率较低

... or perhaps somewhat less efficiently

mytest:
    printf 'Now time is %s\n' "$$(date --iso-seconds)"

其中双美元符号从Make逃脱了美元符号，以便您通过命令替换到达外壳.

where the double dollar sign escapes the dollar sign from Make so that you pass through a command substitution to the shell.

仅指出显而易见的一点，不幸的是，Make使用的语法与Shell的命令替换语法非常相似.在Make内部，使用$(shell command)或$$(command)将command传递给外壳.前者在纯Make片段中是有意义的(Makefile适当的变量定义，等等)；后者仅在配方中可用.

Just to point out the obvious, it is unfortunate that Make uses a syntax which is so similar to the shell's command substitution syntax. Inside Make, you use $(shell command) or $$(command) to pass command to the shell. The former makes sense in pure Make snippets (variable definitions in the Makefile proper, etc); the latter is only available in recipes.

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