Home/ Questions/The oserror: [errno 8] exec format error error: What should you do?
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Julia Bataille
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Asked: 2022-05-17T13:00:27+00:00 In:

The oserror: [errno 8] exec format error error: What should you do?

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As advised, I used some code samples in another forum, but it could not improve the problem. My question is the “oserror: [errno 8] exec format error” in python – how to solve it? The command line is:

import subprocess
 Out = subprocess.Popen(['/usr/local/bin/script', 'hostname = ', 'actual server name', '-p', 'LONGLIST'],shell=True,stdout=subprocess.PIPE,stderr=subprocess.PIPE)

and the result:

OSError: [Errno 8] Exec format error

What does the message mean? Can you advise me to fix it? If you have other better answers, leave them in the answer box below.

oserror
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2 Answers

  1. Best Answer
    Expert

    The cause: The error because at the top of the shell script has no shebang line.

    If you run the command in the shell, there is no error. By default, subprocess.check output() does not run the shell; no subprocess functions run the shell unless asked clearly.

    Solution: You should do the ways like this:

    • Adding /bin/bash at the start of the command or the faulty file
    • Adding shebang #!/bin/sh like in a first-line

    For instance:

    #python -c "import pexpect; p=pexpect.spawn('/bin/bash /usr/local/ssl/bin/openssl_1.1.0f version'); p.interact()"
OpenSSL 1.1.0f 25 May 2017
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  2. OSError: [Errno 8] Exec format error can occur if you don’t have a shebang line at top of your shell script, and you try to execute the script directly. This is an example of the problem: 

    >>> with open('a','w') as f: f.write('exit 0') # create the script
... 
>>> import os
>>> os.chmod('a', 0b111101101) # rwxr-xr-x make it executable 
>>> os.execl('./a', './a') # execute it 
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "/usr/lib/python2.7/os.py", line 312, in execl
 execv(file, args)
OSError: [Errno 8] Exec format error

    You can fix it by adding the shebang, e.g., to a shell script; add #!/bin/sh to the top of your script. 

    >>> with open('a','w') as f: f.write('#!/bin/sh\nexit 0')
... 
>>> os.execl('./a', './a')

    It executes exit 0 with no errors

    Shell parses the command-line on POSIX systems. Your script will not see any spaces around =, e.g. if script: 

    #!/usr/bin/env python
import sys
print(sys.argv)

    Then, run it in the shell 

    $ /usr/local/bin/script hostname = '<hostname>' -p LONGLIST

    produces: 

    ['/usr/local/bin/script', 'hostname', '=', '<hostname>', '-p', 'LONGLIST']

    Note: is not allowed around '='. To escape the redirection metacharacters <>, I have added quotes around <hostname>.

    Run: 

    from subprocess import check_call

cmd = ['/usr/local/bin/script', 'hostname', '=', '<hostname>', '-p', 'LONGLIST']
check_call(cmd)

    Note: no shell=True. You don’t have to escape <>, as no shell is running.

    "Exec format error" could indicate that your script is not in the correct format. Run: 

    $ file /usr/local/bin/script

    Find out more. Compare the architecture to the output of: 

    $ uname -m
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