How do I automate removing a symlink and adding a new one

Question

Basically I want to create a quick set of commands so that I can type into the terminal and have it do this:

cd /path/to/folder/of/symlink
sudo rm -f symlink
sudo ln -s /new/path/of/symlink
cd /new/path/of/symlink

I work for a company whose software is housed in a central location and uses symlinks to work around problems created by working out of a subversion repo branch (or whatever else) since the software relies on specific paths to run. My dilemma is that I tend to have to switch back and forth between various branches and the trunk on a regular basis (several times a day). So what I would like to do is at the very least create some type of script I can run in the terminal and enter a unique command example:

./subchange trunk

or

./subchange branch1

I don't mind having to hardcode the above stuff per folder I need to switch to, or making a unique identifier for each to make my life just a little easier, but I'm not sure how to actually create a script so that I can use it as a custom command or what kind of scripting I would need to use for it to work in linux. So any advice/help would be good for me at this point.

Answer 1

If a script is executable and its parent directory is in your $PATH, then you can use it as a command. For example you can create a bash script out of the commands you mentioned:

#!/bin/bash

cd /path/to/folder/of/symlink
sudo rm -f symlink
sudo ln -s /new/path/of/symlink
cd /new/path/of/symlink

Then you can save that as a file, subchange, and make it executable with chmod +x subchange. I have a directory of scripts on my system (for example /tech/scripts) that I add to my $PATH. Often times the $PATH environment variable is set in a ~/.profile, ~/.bashrc, /etc/bashrc or similar file. You can add your directory by doing:

export PATH=/tech/scripts:$PATH

If you added that to a startup file you'll need to restart your shell or source it (e.g. source ~/.bashrc). Now you can use subchange on the command line and it will execute those commands. To add an argument to the command you can use the $1 operator. In bash this stands for the first argument, so if I do subchange trunk then $1 will be trunk. You can then add this into your script as needed:

#!/bin/bash

cd /path/to/folder/of/symlink
sudo rm -f symlink
sudo ln -s /new/path/$1/symlink
cd /new/path/$1/symlink

The #! at the top of the file is called a shebang (she move... she move...). For a script on a unix system it tells the system what binary to run the following commands through. In this case we're specifying /bin/bash because we want to execute this file as bash commands and the bash binary is in /bin. This could specify another language though and point to its binary.