subprocess.run(["dc", "-e", expression] ,expression可控,如何执行ls -l
时间: 2024-10-12 20:17:25 浏览: 13
`subprocess.run()` 是 Python 中用于运行外部命令的函数,它允许你在脚本中像操作系统的命令行那样执行其他程序。如果你想通过 `subprocess.run` 执行 `ls -l` 命令,你需要提供一个列表作为参数,这个列表的第一个元素是要执行的命令名,其余的是传递给该命令的选项和参数。
如果你想要使用 `subprocess.run` 来执行 `ls -l`,你可以这样做:
```python
import subprocess
# 使用子进程执行 ls -l 命令
command = ["ls", "-l"]
result = subprocess.run(command, capture_output=True, text=True) # 输出结果可能会包含换行符,所以设置text=True以便解析为字符串
# 如果你想查看输出
print(result.stdout)
# 或者获取返回码(0通常表示成功)
print(result.returncode)
```
在这个例子中,`capture_output=True` 参数用于捕获子进程的输出,`text=True` 则确保输出是以文本形式返回的,而不是字节流。
相关问题
subprocess.Popen subprocess.run
subprocess.Popen and subprocess.run are both modules in Python's subprocess module that are used for running external commands. Here's a brief explanation of each:
1. subprocess.Popen: This function is used to create a new process and execute a command within it. It provides more flexibility and control over the execution process. Popen returns a Popen object, which allows you to interact with the running process, such as reading its output or terminating it.
Example usage:
```python
import subprocess
# Run a command and get its output
result = subprocess.Popen(['ls', '-l'], stdout=subprocess.PIPE)
output = result.communicate()
print(output.decode('utf-8'))
```
2. subprocess.run: This function is a higher-level convenience function introduced in Python 3.5. It is used to run a command and wait for it to complete. It returns a CompletedProcess object that provides information about the completed process, such as return code and output.
Example usage:
```python
import subprocess
# Run a command and get its output
result = subprocess.run(['ls', '-l'], capture_output=True, text=True)
print(result.stdout)
```
Both functions can be used to execute external commands, but the choice between them depends on your requirements. Popen offers more flexibility, while run provides a simpler and more straightforward way to execute commands.
result = subprocess.run('adb start-server', stdout=subprocess.PIPE, stderr=subprocess.PIPE).stdout 一直没有返回
如果加上了 `stdout=subprocess.PIPE` 参数,`subprocess.run()` 命令就会将命令的标准输出信息重定向到一个管道中,并且阻塞等待命令执行完成。如果命令一直没有返回,可能是因为命令一直在等待某些条件满足,但是这些条件无法满足,导致命令一直阻塞。
比如,在启动 ADB 服务器之前,你需要确认设备已正确连接并启用开发者模式。如果设备没有启用开发者模式,或者没有授权计算机进行调试,ADB 服务器就无法连接设备,而命令就会一直阻塞等待。
你可以尝试加上 `timeout` 参数,设置命令的超时时间,比如 `timeout=10` 表示等待命令执行完成的最长时间为 10 秒。如果命令在超时时间内没有返回,`subprocess.run()` 命令会抛出 `TimeoutExpired` 异常。你可以在捕获异常后进行相应的处理,比如输出错误信息或者尝试重启设备和计算机。下面是一个示例代码:
```python
import subprocess
try:
result = subprocess.run('adb start-server', stdout=subprocess.PIPE, stderr=subprocess.PIPE, timeout=10)
output = result.stdout.decode('utf-8')
print(output)
except subprocess.TimeoutExpired:
print('Command timed out')
except Exception as e:
print('Error:', e)
```
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