[SOLVED] Bash Script To Concatenate Environmental Variables

Xplorer4x4 · 03-18-2012, 12:27 AM

I have written a bash script and everything works great except for trying to concatenate some variables in to .bashrc and other system files.

I have 4 instances of edits but here i the edit for bashrc:

Code:

cat >> ~/.bashrc <<EOF
export DEVKITXENON="/usr/local/xenon" 
export PATH="$PATH:$DEVKITXENON/bin:$DEVKITXENON/usr/bin" 
EOF

This does actually edit .bashrc, it just does not actually pass the variables in to the file properly. Here is what it outputs:

Code:

export DEVKITXENON="/usr/local/xenon"
export PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/bin:/usr/bin"

grail · 03-18-2012, 12:35 AM

You have 2 issues here:

1. The variable DEVKITXENON has yet to be set at point of execution, hence when the here document is processed it is expanding the variable to nothing

2. If you did not want the variable to expand then the PATH variable will also not be expanded

May I also ask, do you want this variable available to the shell or is it merely to be used to fill in the data for the PATH variable?

Depending on how you answer the above will change the solution.

Xplorer4x4 · 03-18-2012, 12:47 AM

grail, thanks for your response, but keep in mind this is the newbie forum..

1. Assuming I comprehend this correctly, are you saying that the system does not know what DEVKITXENON is because I have not installed a corresponding package for it? If so, that is not the case as I have installed the corresponding package already. If I manually edited .bashrc the system would have no problem comprehending this.

2. ?

I think my original statement was pretty self explanatory. With in a bash scipt, I am trying to use cat to append the two export lines in .bashrc. Where did I go wrong?

grail · 03-18-2012, 03:22 AM

Yes I fully understand that this is a newbie forum and I was trying to tell you where you went wrong

Number 1 has nothing to do with what is installed but rather how and when the variable is being expanded, ie. the name of the variable at this point is irrelevant.
In the current here document you have used, all variables will be expanded by the shell, bash, prior to the rest of the process being run.
Hence you type:

Code:

cat >> ~/.bashrc <<EOF
export DEVKITXENON="/usr/local/xenon" 
export PATH="$PATH:$DEVKITXENON/bin:$DEVKITXENON/usr/bin" 
EOF

And before executing the cat / here document, the shell does:

Code:

cat >> ~/.bashrc <<EOF
export DEVKITXENON="/usr/local/xenon" 
export PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/bin:/usr/bin" 
EOF

So as the shell currently has no idea what DEVKITXENON is to be set to it is presumed to be not currently set and hence null.

My question surrounding whether or not DEVKITXENON needs to be known to the shell at login was regarding whether or not other applications will look for this to know the value, eg. like JAVA_HOME
can be set and recalled by java applications. If it does not need to be known except to set the PATH variable, then I would set the variable prior to running the here document
and forgo the first line:

Code:

DEVKITXENON="/usr/local/xenon"
cat >> ~/.bashrc <<EOF
export PATH="$PATH:$DEVKITXENON/bin:$DEVKITXENON/usr/bin"

Or if you wish you could also put it into the .bashrc file without the export, but then this brings us to option 2.
This option allows you to deliver the variables as is into your .bashrc and choose either to export or not based on the above information.

Assuming yes to the export:

Code:

cat >> ~/.bashrc <<"EOF"
export DEVKITXENON="/usr/local/xenon" 
export PATH="$PATH:$DEVKITXENON/bin:$DEVKITXENON/usr/bin" 
EOF

By placing the quotes around the here document ending you instruct it not to let the shell evaluate the variables and deliver them as written.

Hope this was clearer

Xplorer4x4 · 03-21-2012, 11:27 PM

Thanks Grail, from what I went with the second method and it seems to work great! Thanks again!

grail · 03-22-2012, 12:44 AM

No problem

Please mark as SOLVED if you have a solution

pan64 · 03-22-2012, 02:19 AM

Quote:

Originally Posted by Xplorer4x4

I have written a bash script and everything works great except for trying to concatenate some variables in to .bashrc and other system files.

I have 4 instances of edits but here i the edit for bashrc:

Code:

cat >> ~/.bashrc <<EOF
export DEVKITXENON="/usr/local/xenon" 
export PATH="$PATH:$DEVKITXENON/bin:$DEVKITXENON/usr/bin" 
EOF

I think you simply missed a few backslashes, the second line should look like this:

Code:

export PATH="$PATH:\$DEVKITXENON/bin:\$DEVKITXENON/usr/bin"