I'm currently an intern that's out of their depths here, this is really my first time using Linux, and everything I know comes from basic level tutorials.
I was asked by my boss today to install a program, and I'm following this tutorial on it, but am stuck at the Path part of it.
Solved
Every time I try to do this:
~$ export DTITK_ROOT=${autofs/cluster/name/MyUsername/more/path/DTI-TK/dtitk-2.3.1-Linux-x86-64}/dtitk
Like it told me to.
I get:
bash: DTITK_ROOT=${autofs/cluster/name/MyUsername/more/path/DTI-TK/dtitk-2.3.1-Linux-x86-64}/dtitk: bad substitution
Thank you user Muon
In bash, the ${} syntax can be used to substitute in the value of a previously defined variable, and you've enclosed an explicitly typed-out path within it, so bash is looking for a variable called path/MyUsername/more/path/DTI-TK/dtitk-2.3.1-Linux-x86-64 and not finding it. It should work if you run the command without the substitution:
$ export DTITK_ROOT=/path/to/dtitk
Related
I'm sure this is one of the dumbest problems asked on this site, but I am very new to linux, and a little out of my depths. I'm working off of this tutorial here and am stuck on the "add the path" and verify steps.
For this one the tutorial told me to use this:
export PATH=${PATH}:${DTITK_ROOT}/bin:${DTITK_ROOT}/utilities:${DTITK_ROOT}/scripts
I have already defined DTITK_ROOT, and have a few questions about the above instructions.
Should the ${} be left around the DTITK_ROOT?
My DTITK_ROOT is the full path (I think that's the right term) to the file I extracted the program to, should I change that?
What do I write for ${PATH} in that case? I understand that I'm supposed to replace it with something, but I don't know what. Everything I've tried doesn't pass the verify step.
I'm sorry if it seems like a dumb or really simple question, but I don't even know any keywords to google in order to find how to get the answer.
Yes. This is how you access the path stored in DTITK_ROOT. This is called parameter expansion. You can read more about it here.
No, don't change anything. Also, a more commonly used term is absolute path, in comparison to relative path. The absolute path is a path from the root directory, /. Relative path is a path from your current working directory. You can read more about paths in general and the difference between absolute and relative paths here.
You don't replace it with anything. Once again, parameter expansion comes into play and this will be replaced with what is already stored in your path variable. So really all this command is doing is taking your path variable, adding some more paths to it, and then storing it back into your path variable. If you didn't know, the path variable contains paths to all executable files that you would like to execute without typing the full path. Here is a good discussion on path variables, along with other environment variables.
1st command takes care of path
export DTITK_ROOT=mypathonSystem/dtitk
2nd command
export PATH=${PATH}:${DTITK_ROOT}/bin:${DTITK_ROOT}/utilities:${DTITK_ROOT}/scripts
I am not too sure but I think second command should run as is since you defined DDTITK_ROOT in first command
${PATH} is letting the system know where the resources can be found at
have you tried running first command, then running second command unmodified?
Should the ${} be left around the DTITK_ROOT?
Yes. In the case of the shell, it is not essential here because the / that follows the $DTITK_ROOT is enough to signal that we have reached the end of the variable name, but doing ${DTITK_ROOT} explicitly says that the variable name is DTITK_ROOT and not that plus whatever characters might be on the end of it. Other programs (such as make) which allow you to write shell commands to execute might not be so accommodating - make would think that $DTITK_ROOT would be the value of $D followed by the literal characters TITK_ROOT. So, it is a good practice to just get used to putting {} around shell variable names that are longer than a single character.
My DTITK_ROOT is the full path to the file I extracted the program to, should I change that?
If you mean the full path to the directory that you extracted the program to, then that is what you should use. I am assuming that you have something like "export DTITK_ROOT=/Users/huiz/unix/dtitk" (per the example).
On thing you can do is to verify that the value of DTITK_ROOT is available by executing a "echo ${DTITK_ROOT}" to verify that it has the proper value.
I'm looking for a way to validate the syntax of a bash script without executing it.
bash -n only seems to validate base bash syntax, what I am missing is:
function name validations
un-initialized parameter validations
Any ideas on how to achieve that?
I am also missing the validation of the number of parameters a function takes,
but that sounds like a very hard thing to do in theory, in bash.
In other words what I'd like to do is pretty much take a bash script and "compile" it like I would compile a c++ program.
bash -n is certainly the fundamental way to do that.
However there is also a site that will do some validation for you:
http://www.shellcheck.net/ --And there is a link on the site to the source code if you want to run it locally.
We have put together a perl script that essentially looks at the argument that is being passed to it checks if is creating or modifying a file then it saves that in a mysql database so that it is easily accessible later. Here is the interesting part, how do I make this perl script run before all of the commands typed in the terminal. I need to make this dummy proof so people don't forget to run it.
Sorry I didn't formulate this question properly. What I want to do is prepend to each command such that each command will run like so "./run.pl ls" for example. That way I can track file changes if the command is mv or it creates an out file for example. The script pretty much takes care of that but I just don't know how to run it seamlessly to the user.
I am running ubuntu server with the bash terminal.
Thanks
If I understood correctly you need to execute a function before running every command, something similar to preexec and precmd in zsh.
Unfortunately bash doesn't have a native support for this but you can do it using DEBUG trap.
Here is a sample code applying this method.
This page also provide some useful information.
You can modify the ~/.bashrc file and launch your script there. Do note that each user would (and should) still have the privelege to modify this file, potentially removing the script invocation.
The /etc/bash.bashrc file is system-wide and only changeable by root.
These .bashrcs are executed when a new instance of bash is created (e.g. new terminal).
It is not the same as sh, the system shell, that is dash on Ubuntu systems.
I often find myself taking a lot of time to navigate through my filesystem when using the linux shell. This generally occurs because the autocompletion of bash only works if you provide the start of the file/dirname. What I often end up in is a lot of 'ls' with 'grep' commands, finally doing a 'cd'.
When you use a GUI based filebrowser (like Nautilus) you can type any part of a file/dirname and it will have matches that it jumps to directly. This makes it a lot easier and faster to navigate.
I wonder if anybody knows any great tools that helps with this problem. I know of the existence of Midnight Commander, though I never really used it for real and I couldn't figure out a direct solution for my problem the first couple of times I tried it. Also it seems not suitable because I want to have my shell's current working directory to be changed so I can do stuff there, instead of being stuck in an external program like Midnight Commander.
Try autojmp
https://github.com/joelthelion/autojump
And following article provides another solution
http://jeroenjanssens.com/2013/08/16/quickly-navigate-your-filesystem-from-the-command-line.html
You can first use the autocd or autopushd in zsh. You would just have to type the directory you want to go to, without the hassle of typing cd or pushd everytime.
You also have the globing possibility. For example, if I got those file in a directory:
1-a.tar
1-b.tar
c.tar
I can just type
*a.tar
without caring about the beginning of the file.
As a last solution you can always use an alias to the find command with a personalized option.
i want to make a script (to) that makes it easier for me to enter folders.
so eg. if i type "to apache" i want it to change the current directory to /etc/apache2.
however, when i use the "cd" command inside the script, it seems like it changes the path WITHIN the script, so the path in the shell has not changed.
how could i make this work?
Use an alias or function, or source the script instead of executing it.
BASH FAQ entry #60.
use a function
to_apache(){
cd /etc/apache
}
put in a file eg mylibrary.sh and whenever you want to use it, source the file. eg
#!/bin/bash
source /path/mylibrary.sh
to_apache
As Ignacio said, make it into a function (or perhaps an alias).
The way I tend to do it is have a shell script that creates the function - and the script and the function have the same name. Then once at some point in time, I will source the script ('. funcname') and thereafter I can simply use the function.
I tend to prefer functions to aliases; it is easier to manage arguments etc.
Also, for the specific case of changing directories, I use CDPATH. The trick with using CDPATH is to have the empty entry at the start:
export CDPATH=:/work4/jleffler:/u/jleffler:/work4/jleffler/src:\
/work4/jleffler/src/perl:/work4/jleffler/src/sqltools:/work4/jleffler/lib:\
/work4/jleffler/doc:/u/jleffler/mail:/work4/jleffler/work:/work4/jleffler/ids
On this machine, my main home directory is /work4/jleffler. I can get to most of the relevant sub-directories in one go with 'cd whatever'.
If you don't put the empty entry (or an explicit '.') first, then you can't 'cd' into a sub-directory of the current directory, which is disconcerting at least.
Ignacio Vazquez-Abrams gave a link to what probably answers the question, although I didn't really follow it. The short answer is to use either "source" or a single dot before the command, eg:
. to apache
But, I found there are down problems to this if you have a more complicated script. It seems that the original script filename variable ($0) is lost. I see "-bash" instead, so your script can't echo error text that that would include the full filename.
Also, you can't use the "exit" command, or your shell will exit (especially disconcerting from ssh).
Also, the "basename" function gives an error if you use that.
So, it seems to me that a function might be the only way to get around some of these problems, like if you are passing parameters.