Monthly Archives: October 2016

Uncategorized

Problem: chmod is ignored in the Git Bash prompt

So here’s a strange one that had me baffled for a bit – the chmod command is pretty much a null operation from the Git Bash prompt (MingW64). This initially showed up on a script for launching a Docker container, but as nearly as I can tell, it happens for any shell script.

So, we have a simple script that prints out “Hello World!”.

blair@Squawk MINGW64 ~/test
$ cat foo
echo Hello World!

Simple enough. Now the thing is, I want to make this script executable. Now this particular Bash implementation will let me run ./foo and it’ll execute, but my real use case (running a Docker container) is going to have a somewhat longer name. Just as a matter of convenience, I’d like to to type just the first few characters, press tab, and have the filename expanded. And besides, your executable files should always be marked as executable.

blair@Squawk MINGW64 ~/test
$ ls -l
total 2
-rwxr-xr-x 1 blair 197121 28 Oct 18 00:20 bar*
-rw-r--r-- 1 blair 197121 18 Oct 18 00:10 foo

blair@Squawk MINGW64 ~/test
$

OK, this is an easy fix, I just need to run chmod and set the execute bit to on, right?

blair@Squawk MINGW64 ~/test
$ ls -l
total 2
-rwxr-xr-x 1 blair 197121 28 Oct 18 00:20 bar*
-rw-r--r-- 1 blair 197121 18 Oct 18 00:10 foo

blair@Squawk MINGW64 ~/test
$ chmod 744 foo
blair@Squawk MINGW64 ~/test
$ ls -l
total 2
-rwxr-xr-x 1 blair 197121 28 Oct 18 00:20 bar*
-rw-r--r-- 1 blair 197121 18 Oct 18 00:10 foo

The execute bit didn’t change. Maybe I need to use the u+x syntax instead?

$ chmod u+x foo
blair@Squawk MINGW64 ~/test
$ ls -l
total 2
-rwxr-xr-x 1 blair 197121 28 Oct 18 00:20 bar*
-rw-r--r-- 1 blair 197121 18 Oct 18 00:10 foo

Still no luck. So why is bar marked as executable? What’s the difference between these two scripts? The answer turns out to be one line of code:

blair@Squawk MINGW64 ~/test
$ chmod u+x foo
blair@Squawk MINGW64 ~/test
$ cat bar
#!/bin/sh
echo Hello World!

Do you see that first line, where it says “#!/bin/sh”. That’s how Bash knows what interpreter to pass the script to. It also turns out, in this particular implementation, that’s how Bash knows the file contains an executable script instead of just text.

So we modify foo, and get this result:

blair@Squawk MINGW64 ~/test$ cat foo
#!/bin/sh
echo Hello World!
blair@Squawk MINGW64 ~/test
$ ls -l
total 2
-rwxr-xr-x 1 blair 197121 28 Oct 18 00:20 bar*
-rwxr--r-- 1 blair 197121 18 Oct 18 00:10 foo*

(Image credit: Screenshot by ThatBlairGuy)

Uncategorized

git error: Permission to user-B/repo.git denied to user-A

I have two GitHub accounts: UserA and UserB. Over time I’ve been switching to working with UserB, but the switchover was a bit difficult.

I created a test repository on GitHub at https://github.com/UserB/test

On the local system, from the command prompt

cd \git
git clone https://UserB@github.com/UserB/test
cd test
# make some changes to README.md, add a new foo.txt
git add *
git commit -m "Banana!" # In real life, you'll probably want a more useful comment.

And that’s where the train went off the rails…

C:\git\test>git push
remote: Permission to UserB/test.git denied to UserA.
fatal: unable to access 'https://UserB@github.com/UserB/test/': The requested URL returned error: 403

So git’s saying that even though I expressly got this as UserB, it still thinks I’m UserA

Google came back with lots of stuff about making sure you have the right SSH key (apparently the cool kids do everything over SSH).

A few search results make reference to the Windows Credential Manager. Apparently the Windows version of Git hooks into that somehow. What’s the Windows Credential Manager? Well, from the name, it sounds like something that might be used for storing userids and passwords.

OK, so how do I invoke it? Dunno. Let’s try the search box on the START menu. Aha! Two entries. One for “Credential Manager” and one for “Manage Windows Credentials.”

So let’s try the first one. Hey! This looks promising:

About halfway down the list, there’s one labeled “git:https://github.com” Let’s expand that.

Oh, looky there! Username and password.

Now what I did was to remove the entry and then push again. I was prompted to enter a userid and password. I still had to type the password at the command prompt, but IT STUCK.

C:\git\test>git push
Counting objects: 3, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (2/2), done.
Writing objects: 100% (3/3), 304 bytes | 0 bytes/s, done.
Total 3 (delta 0), reused 0 (delta 0)
To https://github.com/UserB/test
5e74c47..cf2ca13 master -> master

I probably could have clicked “Edit” and changed the userid and password, and just kept going, but I didn’t notice the “Edit” right away.

It looks as though you might actually be able to have multiple entries for git:https://github.com, but I haven’t tried that yet.

(Public domain photo from PublicDomainPictures.net)