如何以编程（shell脚本），确定是否有变化？ [英] How can I programmatically (in a shell script) determine whether or not there are changes?

问题描述

我想创建一个知道如果在当前工作目录更改的Bash脚本。我知道，

I am trying to create a Bash script that knows if there are changes in current working directory. I know that

$ git status

返回类似无犯的消息。什么我想，是一个变量定义为真或假。这个布尔值会告诉我，如果有还是不变化。

returns a message like "nothing to commit". What I am trying to, is to define a variable to true or false. This boolean value will tell me if there are or not changes.

显然，我不是的bash脚本的专家。我想这样的事情，

Obviously I am not an expert of bash scripts. I tried something like this,

there_are_changes=$(git status | grep nothin)
echo $there_are_changes

但预期它不工作。我应该怎么办？

but it doesn't work as expected. What should I do?

推荐答案

的git-DIFF 手册页介绍这里的相关性两种选择：

The git-diff man page describes two options of relevance here:

--quiet
Disable all output of the program. Implies --exit-code.

和

--exit-code
Make the program exit with codes similar to diff(1). That is, it
exits with 1 if there were differences and 0 means no differences.

因此​​，一个强大的方法将是运行

Therefore, a robust approach would be to run

git diff --quiet; nochanges=$?

shell变量 nochanges 将等于 0 （即真）如果没有变化， 1 （即假）除外。

The shell variable nochanges will be equal to 0 (i.e. true) if there are no changes, and 1 (i.e. false) otherwise.

您就可以使用 nochanges 的条件语句的值如下：

You can then use the value of nochanges in conditional statements as follows:

if [ $nochanges -eq 0 ]; then
    # there are no changes
else
    # there are changes
fi

另外，如果你不需要存储在一个变量的退出状态，你可以这样做：

Alternatively, if you don't need to store the exit status in a variable, you can do:

if git diff --quiet; then
    # there are no changes
else
    # there are changes
fi

---

修改：由于 git的差异是瓷的Git命令，并要以编程方式做的事情，你应该使用称为管道的Git命令 git的差异指数代替（其中也有一个 - 安静标志，但必须提供一个树杂交参数）：

---

Edit: Since git diff is a porcelain Git command and you want to do things programmatically, you should probably use the plumbing Git command called git diff-index instead (which also has a --quiet flag, but which must be supplied a tree-ish argument):

if git diff-index --quiet HEAD; then
    # there are no changes
else
    # there are changes
fi

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