调用系统命令

调用一个外部命令并处理输出内容

下面的代码将调用操作系统中的 git log --oneline 命令，然后使用 regex 对它输出到 stdout 上的调用结果进行解析，以获取哈希值和最后 5 条提交信息( commit )。

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调用 python 解释器运行代码并检查返回的错误码

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通过管道来运行外部命令

下面的例子将显示当前目录中大小排名前十的文件和子目录，效果等效于命令 du -ah . | sort -hr | head -n 10。

Command 命令代表一个进程，其中父进程通过 Stdio::piped 来捕获子进程的输出。

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将子进程的 stdout 和 stderr 重定向到同一个文件

下面的例子将生成一个子进程，然后将它的标准输出和标准错误输出都输出到同一个文件中。最终的效果跟 Unix 命令 ls . oops >out.txt 2>&1 相同。

File::try_clone 会克隆一份文件句柄的引用，然后保证这两个句柄在写的时候会使用相同的游标位置。

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持续处理子进程的输出

下面的代码会创建一个管道，然后当 BufReader 更新时，就持续从 stdout 中读取数据。最终效果等同于 Unix 命令 journalctl | grep usb。

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读取环境变量

使用 std::env::var 可以读取系统中的环境变量。

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