在Python中运行shell内置命令

Question

For training, I have idea to write a script which will display the last bash/zsh command.

First of all, I tried with os.system and subprocess to execute history command. But, as you know, history is a shell builtin, so, it doesn't return anything.

Then, I tried this piece of code:

shell_command = 'bash -i -c "history -r; history"' event = Popen(shell_command, shell=True, stdin=PIPE, stdout=PIPE, stderr=STDOUT)

But it have just shown commands from last session. What i want to see is the previous command (which i just typed) I tried cat ~/.bash_history and have same result, unluckily.

Any idea ?

Answer 1

You could use tail to get the last line:

from subprocess import Popen, PIPE, STDOUT

shell_command = 'bash -i -c "history -r; history"'
event = Popen(shell_command, shell=True, stdin=PIPE, stdout=PIPE,
           stderr=STDOUT)
out = Popen(["tail", "-n", "1"], stdin=event.stdout, stdout=PIPE)

output = out.communicate()
print(output[0])

Or just split the output and get the last line:

from subprocess import Popen, PIPE, STDOUT

shell_command = 'bash -i -c "history -r; history"'
event = Popen(shell_command, shell=True, stdin=PIPE, stdout=PIPE,
           stderr=STDOUT)
print(event.communicate()[0].splitlines()[-1])

Or read bash_history :

from os import path
out= check_output(["tail","-n","1",path.expanduser("~/.bash_history")])
print(out)

Or open the file in python and just iterate until you get to the end of the file:

from os import path
with open(path.expanduser("~/.bash_history")) as f:
    for line in f:
        pass
    last = line
    print(last)