于 2012-9-29 19:53, Kushal Kumaran 写道:
On Sat, Sep 29, 2012 at 6:18 AM, 叶佑群<ye.you...@eisoo.com> wrote:
于 2012-9-28 16:16, Kushal Kumaran 写道:
On Fri, Sep 28, 2012 at 1:15 PM, 叶佑群<ye.you...@eisoo.com> wrote:
Hi, all,
I have the shell command like this:
sfdisk -uM /dev/sdb<< EOT
,1000,83
,,83
EOT
I have tried subprocess.Popen, pexpect.spawn and os.popen, but none
of
these works, but when I type this shell command in shell, it is works
fine.
I wonder how to emulate this type of behavior in python , and if someone
can
figure out the reason why?
The sample code of subprocess.Popen is:
command = ["sfdisk", "-uM", target, "<<EOT", "\r\n",
",", 1000, ",", "83", "\r\n",
",", ",", "83", "\r\n", "EOT", "\r\n"]
pobj = subprocess.Popen (command, bufsize=1, \
stderr=subprocess.PIPE, stdout=subprocess.PIPE)
res = pobj.stderr.readline ()
if res is not None and pobj.returncode != 0:
observer.ShowProgress (u"对设备 %s 分区失败！" % target)
return False
The "<<EOT" syntax (called a here-document) just provides input to the
command. If you use the communicate method, you can provide input as
an argument:
command = ["sfdisk", "-uM", target ]
instructions = """
,1000,83
,,83
"""
pobj = subprocess.Popen(command, stdin=subprocess.PIPE,
stdout=subprocess.PIPE, stderr=subprocess.PIPE)
(output, errors) = pobj.communicate(instructions)
I tried this, but it is still not work.
What do you mean by "not work"?
Sorry for replying so late, these days are long vocation in china.
If I type command in shell line by line, the command will run as
expected, but when I invoke the command in python, it is always failed.
Which is what I mean "not work".
- If you get an exception, copy the entire traceback into an email
No exception occured.
- If you do not get an exception, print out the value of the "errors"
variable to see why the command failed. You can also check
pobj.returncode for the exit status of the subprocess.
I solved this problem as below:
fop = os.popen ("sfdisk -uM %s <<EOT\n,%d,83\n,,83\nEOT\n" % (target, fps))
But when I run it with subprocess.Popen (), it doesn't work as os.popen
even use the code as:
command = ["sfdisk", "-uM", target ]
instructions = """
,1000,83
,,83
"""
pobj = subprocess.Popen(command, stdin=subprocess.PIPE,
stdout=subprocess.PIPE, stderr=subprocess.PIPE)
(output, errors) = pobj.communicate(instructions)
stderr.readline () always return the error message means "sfdisk won't accept more
than one device parameter except -s or -l is specified", it seems that some
parameters were incorrectly treated
A possibility is that you have to replace "sfdisk" with the full path
to the binary, if it cannot be located on the PATH. So you will
replace it with "/usr/sbin/sfdisk", or "/sbin/sfdisk", or wherever the
file actually is.
<from your other email>
If I want to read the output line by line and not put all output to memory
buffer in one
time, how to write the code?
You can read line by line by calling pobj.stdout.readline() and
pobj.stderr.readline(). You can send input to the process by calling
pobj.stdin.write(). If you manage this interaction "by hand", you
should not call communicate(). Also, you should be aware of the
problem mentioned in the subprocess documentation:
"Use communicate() rather than .stdin.write, .stdout.read or
.stderr.read to avoid deadlocks due to any of the other OS pipe
buffers filling up and blocking the child process."
Is there any reason why you need to read line-by-line? You could use
communicate(), and then call stdout.splitlines() to get a list of
lines, if that's all you need.
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