Issue in parsing the string output from the command using "subprocess"
srinivasan
srinivasan.rns at gmail.com
Sun Nov 18 14:27:14 EST 2018
Thanks a lot for your quick responses
I tried to fix the issue as below, I verified in my desktop ubuntu
environment, but tomorrow once I can verify on my embedded target, please
let me know if you foresee any issues with the below fix?
def wifi_disconnect(self, timeout=10):
"""
Connect to Access point using SSID and PW.
:param ssid: SSID of the ACCESS POINT.
:param pw: password for connecting to the access point.
:return: command output as True or False.
"""
cmd = "nmcli -t -f TYPE,UUID con"
res = self._helper.execute_cmd_output_string(cmd)
print(res)
lines = res.split("\n")
print(lines)
for line in lines:
parts = line.split(":")
print(parts)
print(parts[0])
if (parts[0] == "802-11-wireless"):
print("------------------------------------------------------")
print("nmcli connection delete uuid " + parts[1])
cmd = "nmcli connection delete uuid '%s'" % parts[1]
for i in range(timeout // 2):
exit_code = self._helper.execute_cmd_return_code(cmd)
print(exit_code)
time.sleep(1)
print "%d seconds have passed" % i
if exit_code == 0:
return True
return False
On Mon, Nov 19, 2018 at 12:50 AM MRAB <python at mrabarnett.plus.com> wrote:
> On 2018-11-18 14:59, srinivasan wrote:
> > Dear Python Experts Team,
> >
> > As am newbie to python and learning python, working on embedded linux
> > platform, my intention is to delete all the SSID's before connecting my
> > Wi-Fi module to specific SSID., I am trying to parse command output using
> > the "subprocess" with wrapper "execute_cmd_output_string" written on
> > it described
> > as below, using the nmcli commands "*nmcli -t -f TYPE,UUID con" and
> "**"nmcli
> > connection delete uuid ".*
> >
> > Could you please help me, what could be the bug in the below method "*def
> > wifi_disconnect_reconnect(self, ssid, pw):" *using the method
> > "execute_cmd_output_string" (in-turn uses "subprocess") which is failing
> to
> > give correct output of., UUID's for *"nmcli connection delete uuid "* ?
> >
> > But which works fine with "commands.getstatusoutput" (res =
> > commands.getstatusoutput("nmcli -t -f TYPE,UUID con")), but I dont want
> to
> > include "commands.getstatusoutput" which costs me for including one more
> > python module in my rootfs
> >
> > Typical output for "nmcli -t -f TYPE,UUID con"
> >
> > ~$ nmcli -t -f TYPE,UUID con
> > 802-11-wireless:3f5011d4-5681-4fed-8dea-95dee790e9e2
> > 802-11-wireless:bfb93be0-740d-426e-b215-0fdc2f652877
> > 802-11-wireless:69b60cf4-65aa-442b-a54c-fb82905adb0d
> > 802-11-wireless:dc2a15ec-d3da-491e-9c8f-cb054f375837
> > 802-11-wireless:5164e7f2-4489-462e-b093-76bc51bf1303
> > 802-11-wireless:d462e8c4-fac7-42f2-8f9a-6846f52d4e8c
> > 802-11-wireless:e5020744-5c9c-453c-92ec-7a854fc893e6
> > 802-11-wireless:eed3358e-8635-471d-b7e9-5c2973a05128
> > 802-11-wireless:ceea6707-a929-4941-9047-a75e061914b6
> > 802-11-wireless:dd6b9c83-db7b-42b9-99c0-14a04f6f35f5
> > 802-11-wireless:9f764fff-6288-49c4-9412-902e89230136
> > 802-11-wireless:72c627cd-77a3-4d16-bb2c-058040d8e4fc
> > ~$
> >
> > *Python Code Snipeet:*
> > *------------------------------*
> > * def wifi_disconnect_reconnect(self, ssid, pw):*
> > * """*
> > * Connect to Access point using SSID and PW.*
> >
> > * :param ssid: SSID of the ACCESS POINT.*
> > * :param pw: password for connecting to the access point.*
> > * :return: command output as True or False.*
> > * """*
> >
> > * cmd = "nmcli -t -f TYPE,UUID con"*
> > * res = self._helper.execute_cmd_output_string(cmd)*
> > * print(res)*
> > * lines = res[1].split('\n') ------------------------> I suspect
> the
> > issue might be here*
> > * print(lines)*
> >
> > * for line in lines:*
> > * parts = line.split(":")*
> > * print(parts)*
> > * print(parts[1])*
> > * if (parts[0] == "802-11-wireless"):*
> > * print("nmcli connection delete uuid "+ parts[1])*
> > * os.system("nmcli connection delete uuid "+ parts[1])*
> >
> > * cmd = "nmcli device wifi connect '%s' password %s" % (ssid, pw)*
> > * exit_code = self._helper.execute_cmd_return_code(cmd)*
> >
> > * return True if exit_code == 0 else False*
> >
> >
> > def execute_cmd_output_string(self, cmd, enable_shell=False):
> > """
> > Execute a command and return its output as a string.
> >
> > :param cmd: abs path of the command with arguments
> > :param enable_shell : force the cmd to be run as shell
> script
> > :return: a string.
> > """
> >
> > try:
> > result = subprocess.check_output(split(cmd),
> > stderr=subprocess.STDOUT,
> > shell=enable_shell)
> >
> > except subprocess.CalledProcessError as e:
> > s = """While executing '{}' something went wrong.
> > Return code == '{}'
> > Return output:\n'{}'
> > """.format(cmd, e.returncode, e.output,
> shell=enable_shell)
> > raise AssertionError(s)
> >
> > return result.strip().decode("utf-8")
> >
> >
> > if __name__ == "__main__":
> > m = wifi()
> > print("disconnect and reconnect")
> > print(m.wifi_disconnect_reconnect("NaWiFi", "abcds"))
> >
> >
> > *Errors:*
> > -----------
> > Traceback (most recent call last):
> > 802-11-wireless:3f5011d4-5681-4fed-8dea-95dee790e9e2
> > 802-11-wireless:dc2a15ec-d3da-491e-9c8f-cb054f375837
> > 802-11-wireless:5164e7f2-4489-462e-b093-76bc51bf1303
> > File
> >
> "/home/srinivasan/Downloads/qa_wifi_nov15_after_incorporating_thilo_comments_zip/qa/test_library/wifi.py",
> > line 153, in <module>
> > 802-11-wireless:d462e8c4-fac7-42f2-8f9a-6846f52d4e8c
> > print(m.wifi_connect("NI WiFi", "T.f.o.s.1996!"))
> > 802-11-wireless:e5020744-5c9c-453c-92ec-7a854fc893e6
> > 802-11-wireless:eed3358e-8635-471d-b7e9-5c2973a05128
> > File
> >
> "/home/srinivasan/Downloads/qa_wifi_nov15_after_incorporating_thilo_comments_zip/qa/test_library/wifi.py",
> > line 77, in wifi_connect
> > 802-11-wireless:ceea6707-a929-4941-9047-a75e061914b6
> > print(parts[1])
> > 802-11-wireless:dd6b9c83-db7b-42b9-99c0-14a04f6f35f5
> > *IndexError: list index out of range*
> > 802-11-wireless:9f764fff-6288-49c4-9412-902e89230136
> > 802-11-wireless:72c627cd-77a3-4d16-bb2c-058040d8e4fc
> > [u'0']
> > [u'0']
> >
> [snip]
> execute_cmd_output_string returns a string, so 'res' will be a string.
>
> For example, res ==
> u'802-11-wireless:3f5011d4-5681-4fed-8dea-95dee790e9e2'.
>
> That means that res[1] == u'0'.
>
> So res[1].split('\n') == [u'0'].
>
> If you follow the code from there, so you'll see that it'll eventually
> raise IndexError.
> --
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>
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