Reading from Linux Command Line with Python

Reading from linux command line with Python

You need to read stdin from the python script.

import sys

data = sys.stdin.read()
print 'Data from stdin -', data

Sample run -

$ date | python test.py
Data from stdin - Wed Jun 17 11:59:43 PDT 2015

Execute a command by reading contents of a text file

This should work:

import subprocess

# read in users and strip the newlines
with open('/tmp/users.txt') as f:
    userlist = [line.rstrip() for line in f]

# get list of commands for each user
cmds = []
for user in userlist:
    cmds.append('smbmap -u {} -p p@ssw0rd -H 192.168.2.10'.format(user))

# results from the commands
results=[]

# execute the commands
for cmd in cmds:
    results.append(subprocess.call(cmd, shell=True))

# check for which worked
for i,result in enumerate(results):
    if result == 0:
        print(cmds[i])

Edit: made it your file path, changed to .format(), checked result == 0 (works for ssh trying passwords)

Edit: forgot to add shell=True

python - read linux command output continuously

You can read the output line by line and process/print it. Meanwhile use p.poll to check if the process has ended.

def get_message(command):
    p = subprocess.Popen(
        command, 
        stdout=subprocess.PIPE,
    )
    while True:
        output = p.stdout.readline()
        if output == '' and p.poll() is not None:
            break
        if output:
            yield output.strip()

Reading the output of a linux command from C

-As I said in the comments, instead of using system or popen, you might use the system pipe command: |.

Using the pipe command means redirecting the output (stdout) of one program to the input (stdin) of another program.

The simple program (program_that_monitors), that I've insert below, rewrites on the console all the output generated by another program (program_to_monitor) piped (pipe is | ) by it.

from command line:

prog_to_monitor | program_that_monitors

With this trivial command, to have the stderr too, it will be necessary to redirect it to the stdout. All very simple:

from command line:

prog_to_monitor 2>&1 | program_that_monitors

where 2>&1 redirects stderr to stdout and | performs pipelining from program_to_monitor to program_that_monitors

Obviously, instead of the part that rewrites the output coming from program_to_monitor, you can insert your control logic.

Here is the very simple C code:

#include <stdio.h>
#include <string.h>
int main()
{
    char buff[1000];

    while( fgets(buff, 1000, stdin) ) {
        printf(">> ");
        fwrite(buff,1,strlen(buff),stdout);
    }

    return 0;
}

How can I run a python code with input on Linux terminal?

You need to use command line arguments.

For example, in the following code:

import sys

print ('# Args:', len(sys.argv))
print ('Argument List:', str(sys.argv))

If you call it from the terminal...

python3 test_args.py ar1 ar2 ar3 ar4 ar5

Gives as a result:

# Args:: 6
Argument List: ['test_args.py', 'ar1', 'ar2', 'ar3', 'ar4', 'ar5']

Reading input file to Python script, using CMD

script.py < example.txt sends the file contents to stdin which can be accessed via sys.stdin. The following works:

import sys

# First try supporting commands formatted like: script.py example.txt
if len(sys.argv) > 1:
    with open(sys.argv[1]) as f:
        contents = f.read()
# Now try supporting: script.py < example.txt
elif sys.stdin:
    contents = ''.join(sys.stdin)
# If both methods failed, throw a user friendly error
else:
    raise Exception('Please supply a file')

print(contents)

But in good old Python fashion, there is a built-in library that can make our life very easy. The library is fileinput, and it will automatically support both methods of reading input that you mentioned:

import fileinput
contents = fileinput.input()
print( ''.join(contents) )

And that works regardless of if you do script.py example.txt or script.py < example.txt or cat example.txt | script.py and you can even do script.py example1.txt example2.txt example3.txt and you will receive the file contents of the different files combined together.

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