Subprocess call with exit status 128

Question

Essentially, I am trying to use a subprocess call to checkout a git commit at a specific sha hash.

However, I keep getting the error subprocess.CalledProcessError: Command '['git', 'checkout', '62bbce43e']' returned non-zero exit status 128.

This is my code below:

with open(filename) as inputfile:
    reader = csv.reader(inputfile, delimiter=",")
    linecount = 0
    for row in reader:
        if linecount == 0:
            linecount += 1
        else:
            repo = str(row[0])
            sha = str(row[2])
            specificfile = str(row[3])
            linenum = int(row[4])
            cl("cd", repo)
            subprocess.check_output(['git', 'checkout', sha])
            print("checkout done")
            git("checkout", "-")

Asked By: paulo

||

Source

Answer 1

A subprocess.check_output() call actually returns the output (and you can also get error output as well by passing a stderr parameter). You may want to have a look at that to see if it gives you an error explaining what happened.

Since you’re getting an exception (meaning the call is not completing hence output may not be returned), you should be able to get the output from one of the exception members:

try:
    output = subprocess.check_output(['git', 'checkout', sha], stderr=subprocess.STDOUT)
except subprocess.CalledProcessError as e:
    print("Exception on process, rc=", e.returncode, "output=", e.output)

One thing I do know is that some git commands tend to return 128 if you’re not actually in a Git repo. So I’d be looking at the path following your cl("cd", repo) line, with:

os.system("pwd")  # use "cd" for Windows.

If that cd of yours is running in a sub-process, that will not affect the current process and therefore you may not necessarily be in a Git repo at all. That would certainly explain the 128 return code.

By way of example, the following transcript shows what happens when I try to run a git command outside of a repo:

>>> try:
...     output = subprocess.check_output(['git', 'checkout', '12345'])
... except subprocess.CalledProcessError as e:
...     print(e.returncode, e.output)
...

128 b'fatal: not a git repository (or any of the parent directories): .gitn'

If it turns out you are in the wrong directory (i.e., the cl("cd", repo) statement is running a sub-process to change directory), you should use the Python-blessed method to change directories ^(a):

import os
os.chdir(path)

That actually changes the directory for the immediate process (the Python interpreter) rather than a transient sub-process.

^(a) This is actually good advice in general – use Python-specific stuff as much as possible (since it’s mostly cross-platform) rather than spawning a sub-shell (which is inherently platform-specific).

Answered By: paxdiablo

Answer 2

Besides the other point—that causing one sub-shell commands to chdir to some other directory does not affect subsequent separate sub-shell or sub-process commands, while calling os.chdir directly affects your process and therefore affects its subprocesses—note that you have two additional options here:

The subprocess functions all accept a keyword cwd argument, whose default is cwd=None. Providing a string here causes Python to os.chdir into the specified directory just for that one subprocess call.

See the details here.
Git itself provides a flag, -C, that tells Git to do its own chdir early on. To invoke git checkout as if it were cd path/to/repo; git checkout, use git -C path/to/repo checkout.

This flag was new in Git version 1.8.5, so if your Git is older than that, you won’t have git -C (but if your Git is older than 2.x it’s long past time to upgrade 🙂 ).

Answered By: torek

Answer 3

For me, running the program from inside the git repo solved the issue.

Answered By: Mohit Gaikwad

Answer 4

For me the issue was that git clone was being called but that the library that I was cloning already existed. So the tool I was using was calling

git clone https://somevendor.org/my-repo

but my-repo was already a non-empty directory that existed. Deleting the existing folder solved the issue.

Answered By: Bram Vanroy

Subprocess call with exit status 128

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