I would like to iterate over `dirs`in a script, but the script will never show more than one (current) folder
Prior to running the code I have cd/pushd a few folders. Running dirs in the terminal window will list more than one folder. If I type the code in the terminal window I will get the whole list of folders. How can I make it work in the script?
Last edited by alexanderb; 03-30-2019 at 07:29 AM..
Reason: >_ icode was the wrong tag, </> wrapping <code> was better
Now, I am stuck at filtering with associative arrays but I will make a separate topic if I cannot solve it.
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Last edited by RudiC; 03-30-2019 at 02:24 PM..
This User Gave Thanks to alexanderb For This Post:
Please become accustomed to provide decent context info of your problem.
It is always helpful to carefully and detailedly phrase a request, and to support it with system info like OS and shell, related environment (variables, directory structures, options), preferred tools, adequate (representative) sample input and desired output data and the logics connecting the two including your own attempts at a solution, and, if existent, system (error) messages verbatim, to avoid ambiguities and keep people from guessing.
Where are you stuck? Running your given script yields
on my system. Even the exotic ${arr[$i]+7} doesn't give an error message (but doesn't evaluate to something sensible either) .
I apologize for the non satisfactory context. I did not solve how to use associative arrays as a lookup table and used an ordinary array instead.
Context, operating system, bash version
More than 20 years ago, at the release of bash 2.0, I redefined the cd function and I have used my own version of cd ever since on various solaris, bsd and linux systems. Typing cd without any arguments would list the top 7 directories of DIRSTACK and typing cd with a number argument would change directory using the DIRSTACK. It was slightly annoying that the top of DIRSTACK did not necessarily contain unique directories but my cd function was good enough for usage and I never got around to refining it.
The other day I noticed that bash has evolved and now has associative arrays which I thought would solve the issue with the potentially repetitive directory listing.
The problem
I do not know how to check if a key already exists in an associative array. The exotic ${arr[$i]+7} was something I tried reading
wiki.nix-pro.com/view/BASH_associative_arrays#Check_if_key_exists
The basic algorithm I want to do is
which in a sample test code would be
The above program yields
but what I expected (hoped) it to print was
The workaround
I rewrote my old cd function using a simple array for lookup instead of an associated array. The performance hit is negligible but it is annoying that I could not get the associated array to work. It was not without pain to implement since I haven't done any bash programming in 20 years. My new cd function seems to work all right though I haven't tested it extensively. I provide it here for context.
Wow, that's intricate and certainly beyond me on first sight. A few comments:
- You don't need to check if an index is already represented in an associative array; just assign it. If it's aready there, it's overwritten, if not, added.
- your cd without parameter naturally lends itself to bash's select statement; see below (as a proof of concept; it just echoes the cd, no error checking etc.). Note the duplicate /usr entry:
Have two 3 files which has list of servers,users and location and base url which is common on every server
A = server1 server2 server3
B = user1 user2 user3
C = dom1 dom2 dom3
baseurl=/opt/SP/
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