Run python script by shebang with `time` command

Run python script by shebang with `time` command

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I have a python script, which I want to be able to run from bash. This is simply solved by shebang. The next step is to implement the time command into the shebang. My best but not the complete successful idea was to use

#!/usr/bin/env -vS bash -c "time /usr/bin/python3 -OO"

which does so sadly not make python interpret the script file and ends in an interactive python session.

The output is

split -S:  ‘bash -c "time /usr/bin/python3 -OO"’
 into:    ‘bash’
     &    ‘-c’
     &    ‘time /usr/bin/python3 -OO’
executing: bash
   arg[0]= ‘bash’
   arg[1]= ‘-c’
   arg[2]= ‘time /usr/bin/python3 -OO’
   arg[3]= ‘./’
Python 3.7.3 (default, Apr  3 2019, 05:39:12)

How can I do the job? Thanks in advance.

You can solve this by creating a secondary bash script, and just invoking it as the shebang.

Kamori@Kamori-PC:/tmp# ./

real    0m0.028s
user    0m0.016s
sys     0m0.000s
Kamori@Kamori-PC:/tmp# cat

Kamori@Kamori-PC:/tmp# cat
#!/usr/bin/env bash

time python3.7

Run Python scripts without explicitly invoking `python`, There are two things you need to do: Make sure the file is executable: chmod +x Use a shebang to let the kernel know what interpreter to use. The top  With execution permissions and the shebang line properly configured, you can run the script by simply typing its filename at the command-line. Finally, you need to note that if your script isn’t located at your current working directory, you’ll have to use the file path for this method to work correctly.

You cannot do that with a shebang, because it's format (on Linux) is:

#!interpreter [optional-arg]

And this argument is passed as single string (see "Interpreter scripts" and "Interpreter scripts" in the linked document). In other words, you cannot pass multiple arguments (unless they can be concatenated to a single string) to an interpreter. This is down to kernel implementation of how code gets executed.

Using env -S is also not helpful here, because as you can see in your debugging output:

   arg[0]= ‘bash’
   arg[1]= ‘-c’
   arg[2]= ‘time /usr/bin/python3 -OO’
   arg[3]= ‘./’

It runs shell, tells to run a command (-c) starting python wrapped in time and then passed ‘./’ to bash (not python) as its last argument. meaning of which is (applying to the bash):


If the -c option is present, then commands are read from the first non-option argument command_string. If there are arguments after the command_string, the first argument is assigned to $0 and any remaining arguments are assigned to the positional parameters. The assignment to $0 sets the name of the shell, which is used in warning and error messages.

As for you objective. You could create a wrapper that is used as an interpreter in place of env in your case that does desired actions and passed the script to an actual interpreter.

How to Run a Python Script? (Step by Step Tutorial, with Example), You can write and run python scripts from the command line. Just use the When working on data science projects, you'll write Python code all the time… You know that The shebang line for Python3 scripts looks like this: Subscribe to this blog. Follow by Email Random GO~

I guess you already simply tried

#!/usr/bin/time python3

Was it not ok? (i.e. is the -OO in your tests mandatory?)


$ cat
#!/usr/bin/time python3
import sys
print (sys.argv)

$ ./ 
0.01user 0.00system 0:00.02elapsed 95%CPU (0avgtext+0avgdata 9560maxresident)k
0inputs+0outputs (0major+1164minor)pagefaults 0swaps

Although this doesn't solve the -OO yet

Python Tutorial: Execute a Script, This chapter shows how to execute a Python script or program. We start a Python interactive shell in a terminal with the command "python". as in the first shebang line, the interpreter is searched for and located at the time the script is run. If you can't execute or run a Python script, then programming is pointless. When you run a Python script, the interpreter converts a Python program into something that that the computer can understand. Executing a Python program can be done in two ways: calling the Python interpreter with a shebang line, and using the interactive Python shell.

At the end summing up all helpful details from here, I was able to reach my goal with the following solution.

  1. Installing time utiliy by running sudo apt install time
  2. Using the shebang #!/usr/bin/env -S /usr/bin/time /usr/bin/python3 -OO

And now all is running the way I was looking for.

How to Run Your Python Scripts – Real Python, How to Run Python Scripts Using the Command-Line Upon completion you will receive a score so you can track your learning progress over time: combination​, which is commonly called hash bang or shebang, and continues with the path  This quick tutorial shows you how to execute shell commands in Python. Python is an excellent scripting language. More and more sysadmins are using Python scripts to automate their work. Since the sysadmin tasks involve Linux commands all the time, running Linux commands from the Python script is a great help.

Running a Python Script in the Background, If you did not add a shebang to the file you can instead run the script with this command: nohup python /path/to/ &. The output will be  Python is a wonderful language for scripting and automating workflows and it is packed with useful tools out of the box with the Python Standard Library. A common thing to do, especially for a sysadmin, is to execute shell commands. But what usually will end up in a bash or batch file, can be also done in Python. You’ll learn here how to do just that with the os and subprocess modules.

Running Programs, You will be able to run Python scripts from IDLE without the shebang line, but the Use the -3 command line argument to make py.exe run the latest Python 3 to type the full absolute path for the Python program every time you want to run it. When a script’s first line starts with a shebang, what follows a shebang is used as the interpreter for the commands listed in the script. “/bin/bash” in the above example.

How Do I Make My Own Command-Line Commands Using Python , The Python script you just wrote would make a great little command-line type python all the time to launch your program gets daunting fast. So instead it takes a wild guess and tries to run your Python script like a shell to your advantage by adding a shebang line that points to the system Python interpreter:. Starting a Script With #! It is called a shebang or a "bang" line. It is nothing but the absolute path to the Bash interpreter. It consists of a number sign and an exclamation point character (#!), followed by the full path to the interpreter such as /bin/bash. All scripts under Linux execute using the interpreter specified on a first line.