Question

I’m using msysgit on Windows and wrote a simple shell script that I would like to use. I added the folder that the .sh file is in to the PATH variable of my Windows computer but when I want to use my script I have to type rd.sh instead of just plain rd.

How do I use this by just referring to its name rd and not the full file name with the .sh file extension (rd.sh)?

Answer 1

The shell provided with msysgit is bash, which runs in an emulated Unix-like environment.

If you’re running the script from the bash shell, you need to type the name of the script, which as far as the Unix-like environment is concerned is rd.sh. The .sh has no particular meaning in a Unix environment; it’s just the last three characters of the file name. The first line of the script should be #!/bin/sh or #!/bin/bash; this is known as a “shebang”.

On the other hand, if you want to run it from Windows (say, from a cmd.exe command prompt), then the .sh extension is used by Windows to determine how to execute it, and you can invoke it as rd if (a) it’s in a directory in your %PATH%, and (b) Windows is configured (in Folder Options and/or by setting %PATHEXT%) to use sh or bash to launch .sh files.

If you want to be able to run the same script from either environment, you can create a symbolic link that will be recognized in the emulated Unix-like environment. For example, if rd.sh is in $HOME/bin, then this:

ln -s $HOME/bin/rd.sh $HOME/bin/rd

will create the appropriate symlink. (You could make rd a copy of rd.sh, but then changes to one won’t apply to the other.)

If you only need to run it from bash, just call it rd rather than rd.sh; as I mentioned, as far as bash is concerned the .sh extension is just part of the name and has no particular significance. It’s the #! line, not the .sh extension, that tells bash how to execute the script.

(Well, strictly speaking it’s not bash that handles the #!. On actual Unix or Linux systems, it’s handled by the kernel; I’m not sure what the exact mechanism is under msysgit.)