如何将字符串传递到 subprocess.Popen(使用 stdin 参数)?

问题描述

如果我执行以下操作:

导入子流程从 cStringIO 导入 StringIOsubprocess.Popen(['grep','f'],stdout=subprocess.PIPE,stdin=StringIO('one\ntwo\nthree\nfour\nfive\nsix\n')).communicate()[0]

我明白了:

回溯(最近一次调用最后一次):文件<stdin>"，第 1 行，在 ?文件/build/toolchain/mac32/python-2.4.3/lib/python2.4/subprocess.py"，第 533 行，在 __init__ 中(p2cread, p2cwrite,文件/build/toolchain/mac32/python-2.4.3/lib/python2.4/subprocess.py"，第 830 行，在 _get_handles 中p2cread = stdin.fileno()AttributeError: 'cStringIO.StringI' 对象没有属性 'fileno'

显然，cStringIO.StringIO 对象并没有足够接近文件鸭以适应 subprocess.Popen.我该如何解决这个问题?

解决方案

Popen.communicate() 文档:

注意，如果你想发送数据到进程的标准输入，你需要创建 Popen 对象标准输入=管道.同样，要得到任何东西除了结果元组中的 None 之外，你需要给 stdout=PIPE 和/或stderr=PIPE 也是.

替换 os.popen*

 pipe = os.popen(cmd, 'w', bufsize)# ==>pipe = Popen(cmd, shell=True, bufsize=bufsize, stdin=PIPE).stdin

警告 使用communication() 而不是stdin.write(), stdout.read() 或stderr.read() 避免死锁到任何其他操作系统管道缓冲区填满和阻挡孩子过程.

所以你的例子可以写成如下:

from subprocess import Popen, PIPE, STDOUTp = Popen(['grep', 'f'], stdout=PIPE, stdin=PIPE, stderr=STDOUT)grep_stdout = p.communicate(input=b'one\ntwo\nthree\nfour\nfive\nsix\n')[0]打印(grep_stdout.decode())# ->四# ->五# ->

---

在 Python 3.5+(encoding 为 3.6+)上，您可以使用 subprocess.run，将输入作为字符串传递给外部命令并获取其退出状态，并在一次调用中将其输出作为字符串返回:

#!/usr/bin/env python3从子进程导入运行，PIPEp = run(['grep', 'f'], stdout=PIPE,input='one\ntwo\nthree\nfour\n5\nsix\n', encoding='ascii')打印(p.returncode)# ->0打印(p.stdout)# ->四# ->五# ->

If I do the following:

import subprocess
from cStringIO import StringIO
subprocess.Popen(['grep','f'],stdout=subprocess.PIPE,stdin=StringIO('one\ntwo\nthree\nfour\nfive\nsix\n')).communicate()[0]

I get:

Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "/build/toolchain/mac32/python-2.4.3/lib/python2.4/subprocess.py", line 533, in __init__
    (p2cread, p2cwrite,
  File "/build/toolchain/mac32/python-2.4.3/lib/python2.4/subprocess.py", line 830, in _get_handles
    p2cread = stdin.fileno()
AttributeError: 'cStringIO.StringI' object has no attribute 'fileno'

Apparently a cStringIO.StringIO object doesn't quack close enough to a file duck to suit subprocess.Popen. How do I work around this?

解决方案

Popen.communicate() documentation:

    pipe = os.popen(cmd, 'w', bufsize)
    # ==>
    pipe = Popen(cmd, shell=True, bufsize=bufsize, stdin=PIPE).stdin

So your example could be written as follows:

from subprocess import Popen, PIPE, STDOUT

p = Popen(['grep', 'f'], stdout=PIPE, stdin=PIPE, stderr=STDOUT)
grep_stdout = p.communicate(input=b'one\ntwo\nthree\nfour\nfive\nsix\n')[0]
print(grep_stdout.decode())
# -> four
# -> five
# ->

---

On Python 3.5+ (3.6+ for encoding), you could use subprocess.run, to pass input as a string to an external command and get its exit status, and its output as a string back in one call:

#!/usr/bin/env python3
from subprocess import run, PIPE

p = run(['grep', 'f'], stdout=PIPE,
        input='one\ntwo\nthree\nfour\nfive\nsix\n', encoding='ascii')
print(p.returncode)
# -> 0
print(p.stdout)
# -> four
# -> five
# ->

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