What is the best way to execute the below command in Python in a single line?
echo $(readlink /sys/dev/block/$(mountpoint -d /))
Tried using individual os.system(cmd) by separating - "mountpoint -d /" first and taking the output and appending to "readlink /sys/dev/block/${0}".format(out.strip()) and doing an echo works. Tried using subprocess and subprocess.Popen and subprocess.check_output but it raises raise CalledProcessError
cmd = "echo $(readlink /sys/dev/block/$(mountpoint -d /))"
You have to call the subcommand separately. And you can use python methods to read the link:
import subprocess
import os
path = "/"
device = subprocess.run(["mountpoint", "-d", path], stdout=subprocess.PIPE, encoding="utf8").stdout.strip()
link = os.readlink("/sys/dev/block/" + device)
print(link)
You probably want to use something like the following:
cmd = "bash -c 'echo $(readlink /sys/dev/block/$(mountpoint -d /))'"
echo doesn't substitute $() blocks, that's what your shell does, so you have to call the shell. os.system(cmd) should work then.
Related
I wish to run a script, lets call it api.sh. The script takes various arguments,
-t token
-r rules.json
-s data.json
and it is going to create a new json file, e.g. data_2.json.
When I run this in terminal I use the following command:
./api.sh -t token -r rules.json -s data.json > data_2.json
However, I wish to run this command line in Python. Any suggestions are appreciated.
Thanks,
I don't know if it supports python but you can use getopts.
Look here
Does this test.py work:
import subprocess
from subprocess import Popen
path_to_output_file = 'data_2.json'
myoutput = open(path_to_output_file,'w+')
p = Popen(["./api.sh", "-t" , "token", "-r", "rules.json", "-s", "data.json"], stdout=myoutput, stderr=subprocess.PIPE, universal_newlines=True)
output, errors = p.communicate()
You can refer to this for details.
I have written a python script which includes this line:
response = subprocess.check_output(['/usr/bin/sudo /bin/su - backup -c "/usr/bin/ssh -q -o StrictHostKeyChecking=no %s bash -s" <<\'EOF\'\nPATH=/usr/local/bin:$PATH\nmvn --version|grep -i Apache|awk \'{print $3}\'|tr -d \'\n\'\nEOF' % i], shell=True)
This is in a for loop that goes through a list of hostnames and each one I want to check the result of the command on it. This works fine when I run it myself, however, this script is to be run by a system user (shinken - a nagios fork) and at that point I hit an issue.
shinken ALL=(ALL) NOPASSWD: ALL
However, I wanted to restrict the user to only allow it to run as the backup user:
shinken ALL=(backup) NOPASSWD: ALL
But when I run the script I get:
sudo: no tty present and no askpass program specified
I have read around this and tried a few things to fix it. I tried adding -t to my ssh command, but that didn't help. I believe I should be able to run the command with something similar to:
response = subprocess.check_output(['/usr/bin/sudo -u backup """ "/usr/bin/ssh -q -o StrictHostKeyChecking=no %s bash -s" <<\'EOF\'\nPATH=/usr/local/bin:$PATH\njava -version|grep -i version|awk \'{print $3}\'|tr -d \'\n\'\nEOF""" ' % i], shell=True)
But then I get this response:
subprocess.CalledProcessError: Command '['/usr/bin/sudo -u backup """ "/usr/bin/ssh -q -o StrictHostKeyChecking=no bamboo-agent-01 bash -s" <<\'EOF\'\nPATH=/usr/local/bin:$PATH\njava -version|grep -i version|awk \'{print $3}\'|tr -d \'\n\'\nEOF""" ']' returned non-zero exit status 1
If I run the command manually I get:
sudo: /usr/bin/ssh: command not found
Which is strange because that's where it lives.... I've no idea if what I'm trying is even possible. Thanks for any suggestions!
As for sudo:
shinken ALL=(backup) NOPASSWD: ALL
...only works when you switch directly from shinken to backup. You aren't doing that here. sudo su - backup is telling sudo to switch to root, and to run the command su - backup as root. Obviously, then, if you're going to use sudo su (which I've advised against elsewhere), you need your /etc/sudoers configuration to support that.
Because your /etc/sudoers isn't allowing direct the switch to root you're requesting, it's trying to prompt for a password, which requires a TTY, which is thus causing a failure.
Below, I'm rewriting the script to switch directly from shinken to backup, without going through root and running su:
As for the script:
import subprocess
remote_script='''
PATH=/usr/local/bin:$PATH
mvn --version 2>&1 | awk '/Apache/ { print $3 }'
'''
def maven_version_for_host(hostname):
# storing the command lets us pass it when constructing a CalledProcessError later
# could move it directly into the Popen creation if you don't need that.
cmd = [
'sudo', '-u', 'backup', '-i', '--',
'ssh', '-q', '-o', 'StrictHostKeyChecking=no', str(hostname),
'bash -s' # arguments in remote-command position to ssh all get concatenated
# together, so passing them as one command aids clarity.
]
proc = subprocess.Popen(cmd,
stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
response, error_string = proc.communicate(remote_script)
if proc.returncode != 0:
raise subprocess.CalledProcessError(proc.returncode, cmd, error_string)
return response.split('\n', 1)[0]
I have a ssh command which I was using in a system() statement but I want to replace it with a subprocess.call() statement. My ssh command is:
cmd ="ssh -i pem-file.pem user#" + hostname + " 'cd /user/home/ && java -cp jar-file.jar com.packg.class -a opt1 -f text-file_" + ts + ".txt'"
system(cmd)
I want to replace above with a subprocess.call() statement as it is giving me some performance issues and I read that subprocess.call() is a much better option to use. I formulated this query but it is not executing:
result = subprocess.call(["ssh","-i", "pem-file.pem","user#" + hostname + " 'cd /user/home/ && java -cp jar-file.jar com.packg.class -a opt1 -f text-file_" + ts + ".txt'"])
What is the mistake I am doing and what is the correct syntax?
The function shlex.split() is useful for parsing command line arguments into the proper format. This should resolve your syntax error:
import shlex
import subprocess
cmd ="ssh -i pem-file.pem user#" + hostname + " 'cd /user/home/ && java -cp jar-file.jar com.packg.class -a opt1 -f text-file_" + ts + ".txt'"
result = subprocess.call(shlex.split(cmd))
If that doesn't fix your error, then you can pass subprocess.call the shell=True argument:
import subprocess
cmd ="ssh -i pem-file.pem user#" + hostname + " 'cd /user/home/ && java -cp jar-file.jar com.packg.class -a opt1 -f text-file_" + ts + ".txt'"
result = subprocess.call(cmd, shell=True)
Using the shell argument will cause your command to be executed through a shell, rather than having the interpreter parse it. However, don't use the shell option if cmd can ever come from an untrusted source. Take at look at the warning in the Python docs.
One more note:
subprocess.system() is newer and more flexible than os.system(), but don't worry too much about "upgrading" to the new function. The advantages of subprocess.call() are in the more flexible options for communicating with your subprocess. If all you're doing is executing a single command and getting the return code, os.system() is probably fine. If you're finding that your command is being flaky and unreliable, switching to subprocess.call() probably isn't going to help much.
Assuming there are no shell meta-characters in hostname (likely), your command could look like this: each command-line argument is a separate list item:
#!/usr/bin/env python
import subprocess
cmd = ["ssh", "-i", "pem-file.pem", "user#" + hostname,
"cd /user/home/ && java -cp jar-file.jar com.packg.class -a opt1 "
"-f text-file_" + ts + ".txt"]
subprocess.check_call(cmd)
Unlike os.system(); it doesn't run the (local) shell.
You could get the argument list using shlex.split(your_original_system_command) (mentioned by #skrrgwasme) but shlex.split() can be fooled and therefore it is mostly useful as a hint on how the result should look like.
I have to run isql command using python.
Currently i'm doing it in this way
ps = subprocess.Popen("""./isql -I /app/sybase/interfaces_global -S %s -U %s -P %s -D %s -s "|" -w 99999 <<EOF
SET NOCOUNT ON
%s
go
EOF""" %(mdbserver,muserid,mpassword,mdatabase,User_Query),stdout=subprocess.PIPE,shell=True,cwd=sybase_path)
But this method is dependent on the /tmp directory of my server because of the here document, everytime when i run it, it creates a tmp file in the /tmp directory and when the /tmp directory is full the script fails to run the Query onto the database.
How can i use the same command with shell=False, So that i can get rid of the here document """ and the temporary file creation.
this doesn't works
ps = subprocess.Popen("./isql","-I","/app/sybase/interfaces_global","-S",mdbserver,"-U",muserid,"-P",mpassword,"-D",mdatabase,"-s","|","-w","99999","\nSET NOCOUNT ON\n",User_Query,"\ngo",stdout=subprocess.PIPE,shell=False,cwd=sybase_path)
You could replace the here-document by setting stdin=PIPE and providing the input as a string using .communicate() method as #Hans Then suggested:
from subprocess import Popen, PIPE
from textwrap import dedent
isql = Popen(['./isql', '-I', '/app/sybase/...',
'-S', mdbserver,
'-U', muserid, ...,
'-w', '99999'], stdin=PIPE, stdout=PIPE, cwd=sybase_path)
output = isql.communicate(dedent("""\
SET NOCOUNT ON
{}
go
""".format(User_Query)))[0]
Check out the subprocess communicate() command. You can use it to send isql commands to the interpreter.
I'm trying to execute a rsync command via subrocess & popen. Everything's ok until I don't put the rsh subcommand where things go wrong.
from subprocess import Popen
args = ['-avz', '--rsh="ssh -C -p 22 -i /home/bond/.ssh/test"', 'bond#localhost:/home/bond/Bureau', '/home/bond/data/user/bond/backups/']
p = Popen(['rsync'] + args, shell=False)
print p.wait()
#just printing generated command:
print ' '.join(['rsync']+args)
I've tried to escape the '--rsh="ssh -C -p 22 -i /home/bond/.ssh/test"' in many ways, but it seems that it's not the problem.
I'm getting the error
rsync: Failed to exec ssh -C -p 22 -i /home/bond/.ssh/test: No such file or directory (2)
If I copy/paste the same args that I output at the time, I'm getting a correct execution of the command.
Thanks.
What happens if you use '--rsh=ssh -C -p 22 -i /home/bond/.ssh/test' instead (I removed the double quotes).
I suspect that this should work. What happens when you cut/paste your line into the commandline is that your shell sees the double quotes and removes them but uses them to prevent -C -p etc. from being interpreted as separate arguments. when you call subprocess.Popen with a list, you've already partitioned the arguments without the help of the shell, so you no longer need the quotes to preserve where the arguments should be split.
Having the same problem, I googled this issue extensively. It would seem you simply cannot pass arguments to ssh with subprocess. Ultimately, I wrote a shell script to run the rsync command, which I could pass arguments to via subprocess.call(['rsyncscript', src, dest, sshkey]). The shell script was: /usr/bin/rsync -az -e "ssh -i $3" $1 $2
This fixed the problem.