Issue #16624: `subprocess.check_output` now accepts an `input` argument,
allowing the subprocess's stdin to be provided as a (byte) string.
Patch by Zack Weinberg.
diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index f69b42a..78907e0 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -175,6 +175,9 @@
>>> output = subprocess.check_output(["ls", "-l", "/dev/null"])
+ There is an additional optional argument, "input", allowing you to
+ pass a string to the subprocess's stdin. If you use this argument
+ you may not also use the Popen constructor's "stdin" argument.
Exceptions
----------
@@ -563,14 +566,31 @@
... stderr=STDOUT)
b'ls: non_existent_file: No such file or directory\n'
+ There is an additional optional argument, "input", allowing you to
+ pass a string to the subprocess's stdin. If you use this argument
+ you may not also use the Popen constructor's "stdin" argument, as
+ it too will be used internally. Example:
+
+ >>> check_output(["sed", "-e", "s/foo/bar/"],
+ ... input=b"when in the course of fooman events\n")
+ b'when in the course of barman events\n'
+
If universal_newlines=True is passed, the return value will be a
string rather than bytes.
"""
if 'stdout' in kwargs:
raise ValueError('stdout argument not allowed, it will be overridden.')
+ if 'input' in kwargs:
+ if 'stdin' in kwargs:
+ raise ValueError('stdin and input arguments may not both be used.')
+ inputdata = kwargs['input']
+ del kwargs['input']
+ kwargs['stdin'] = PIPE
+ else:
+ inputdata = None
with Popen(*popenargs, stdout=PIPE, **kwargs) as process:
try:
- output, unused_err = process.communicate(timeout=timeout)
+ output, unused_err = process.communicate(inputdata, timeout=timeout)
except TimeoutExpired:
process.kill()
output, unused_err = process.communicate()
diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
index 28f6935..6d8afaf 100644
--- a/Lib/test/test_subprocess.py
+++ b/Lib/test/test_subprocess.py
@@ -158,8 +158,28 @@
stderr=subprocess.STDOUT)
self.assertIn(b'BDFL', output)
+ def test_check_output_stdin_arg(self):
+ # check_output() can be called with stdin set to a file
+ tf = tempfile.TemporaryFile()
+ self.addCleanup(tf.close)
+ tf.write(b'pear')
+ tf.seek(0)
+ output = subprocess.check_output(
+ [sys.executable, "-c",
+ "import sys; sys.stdout.write(sys.stdin.read().upper())"],
+ stdin=tf)
+ self.assertIn(b'PEAR', output)
+
+ def test_check_output_input_arg(self):
+ # check_output() can be called with input set to a string
+ output = subprocess.check_output(
+ [sys.executable, "-c",
+ "import sys; sys.stdout.write(sys.stdin.read().upper())"],
+ input=b'pear')
+ self.assertIn(b'PEAR', output)
+
def test_check_output_stdout_arg(self):
- # check_output() function stderr redirected to stdout
+ # check_output() refuses to accept 'stdout' argument
with self.assertRaises(ValueError) as c:
output = subprocess.check_output(
[sys.executable, "-c", "print('will not be run')"],
@@ -167,6 +187,20 @@
self.fail("Expected ValueError when stdout arg supplied.")
self.assertIn('stdout', c.exception.args[0])
+ def test_check_output_stdin_with_input_arg(self):
+ # check_output() refuses to accept 'stdin' with 'input'
+ tf = tempfile.TemporaryFile()
+ self.addCleanup(tf.close)
+ tf.write(b'pear')
+ tf.seek(0)
+ with self.assertRaises(ValueError) as c:
+ output = subprocess.check_output(
+ [sys.executable, "-c", "print('will not be run')"],
+ stdin=tf, input=b'hare')
+ self.fail("Expected ValueError when stdin and input args supplied.")
+ self.assertIn('stdin', c.exception.args[0])
+ self.assertIn('input', c.exception.args[0])
+
def test_check_output_timeout(self):
# check_output() function with timeout arg
with self.assertRaises(subprocess.TimeoutExpired) as c: