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• Finding the shortest path through a digraph that visits all nodes

  - by Boluc Papuccuoglu

  I am trying to find the shortest possible path that visits every node through a graph (a node may be visited more than once, the solution may pick any node as the starting node.). The graph is directed, meaning that being able to travel from node A to node B does not mean one can travel from node B to node A. All distances between nodes are equal. I was able to code a brute force search that found a path of only 27 nodes when I had 27 nodes and each node had a connection to 2 or 1 other node. However, the actual problem that I am trying to solve consists of 256 nodes, with each node connecting to either 4 or 3 other nodes. The brute force algorithm that solved the 27 node graph can produce a 415 node solution (not optimal) within a few seconds, but using the processing power I have at my disposal takes about 6 hours to arrive at a 402 node solution. What approach should I use to arrive at a solution that I can be certain is the optimal one? For example, use an optimizer algorithm to shorten a non-optimal solution? Or somehow adopt a brute force search that discards paths that are not optimal? EDIT: (Copying a comment to an answer here to better clarify the question) To clarify, I am not saying that there is a Hamiltonian path and I need to find it, I am trying to find the shortest path in the 256 node graph that visits each node AT LEAST once. With the 27 node run, I was able to find a Hamiltonian path, which assured me that it was an optimal solution. I want to find a solution for the 256 node graph which is the shortest.

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• Using Traveling Salesman Solver to Decide Hamiltonian Path

  - by Firas Assaad

  This is for a project where I'm asked to implement a heuristic for the traveling salesman optimization problem and also the Hamiltonian path or cycle decision problem. I don't need help with the implementation itself, but have a question on the direction I'm going in. I already have a TSP heuristic based on a genetic algorithm: it assumes a complete graph, starts with a set of random solutions as a population, and works to improve the population for a number of generations. Can I also use it to solve the Hamiltonian path or cycle problems? Instead of optimizing to get the shortest path, I just want to check if there is a path. Now any complete graph will have a Hamiltonian path in it, so the TSP heuristic would have to be extended to any graph. This could be done by setting the edges to some infinity value if there is no path between two cities, and returning the first path that is a valid Hamiltonian path. Is that the right way to approach it? Or should I use a different heuristic for Hamiltonian path? My main concern is whether it's a viable approach since I can be somewhat sure that TSP optimization works (because you start with solutions and improve them) but not if a Hamiltonian path decider would find any path in a fixed number of generations. I assume the best approach would be to test it myself, but I'm constrained by time and thought I'd ask before going down this route... (I could find a different heuristic for Hamiltonian path instead)

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• Passing PATH through sudo

  - by whitequark

  In short: how to make sudo not to flush PATH everytime? I have some websites deployed on my server (Debian testing) written with Ruby on Rails. I use Mongrel+Nginx to host them, but there is one problem that comes when I need to restart Mongrel (e.g. after making some changes). All sites are checked in VCS (git, but it is not important) and have owner and group set to my user, whereas Mongrel runs under the, huh, mongrel user that is severely restricted in it's rights. So Mongrel must be started under root (it can automatically change UID) or mongrel. To manage mongrel I use mongrel_cluster gem because it allows starting or stopping any amount of Mongrel servers with just one command. But it needs the directory /var/lib/gems/1.8/bin to be in PATH: this is not enough to start it with absolute path. Modifying PATH in root .bashrc changed nothing, tweaking sudo's env_reset and keepenv didn't either. So the question: how to add a directory to PATH or keep user's PATH in sudo?

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• concatenate files including path in header - path contains spaces

  - by manolo

  I have to concatenate a number of files in a directory structure which contains spaces in the folder names looking like this: ./CH 0000100014/A10/11XT/11xt#001.csv find . -name "*.csv" -type f -print0 | xargs -0 cat > allmycsv.txt does the job, however now I need to include the information contained in the path, i.e. CH 0000100014/A10/11XT as a header of each inputfile to cat. find . -name "*.csv" -type f -print0 | xargs -0 -I % sh -c 'echo %; cat %' >allmycsv.txt would do the job, if I had no spaces in the path, but in my case, cat does not get along with the space in the path name. Is there a way out? Cheers, E P.S. I am working on bash on OSX

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• Getting PATH right for python after MacPorts install

  - by BenjaminGolder

  I can't import some python libraries (PIL, psycopg2) that I just installed with MacPorts. I looked through these forums, and tried to adjust my PATH variable in $HOME/.bash_profile in order to fix this but it did not work. I added the location of PIL and psycopg2 to PATH. I know that Terminal is a version of python in /usr/local/bin, rather than the one installed by MacPorts at /opt/local/bin. Do I need to use the MacPorts version of Python in order to ensure that PIL and psycopg2 are on sys.path when I use python in Terminal? Should I switch to the MacPorts version of Python, or will that cause more problems? In case it is helpful, here are more facts: PIl and psycopg2 are installed in /opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages which pythonreturns/usr/bin/python echo $PATHreturns (I separated each path for easy reading): :/opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/ :/opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages :/opt/local/bin :/opt/local/sbin :/usr/local/git/bin :/usr/bin :/bin :/usr/sbin :/sbin :/usr/local/bin :/usr/local/git/bin :/usr/X11/bin :/opt/local/bin in python, sys.path returns: /Library/Frameworks/SQLite3.framework/Versions/3/Python /Library/Python/2.6/site-packages/numpy-override /Library/Frameworks/GDAL.framework/Versions/1.7/Python/site-packages /Library/Frameworks/cairo.framework/Versions/1/Python /System/Library/Frameworks/Python.framework/Versions/2.6/lib/python26.zip /System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6 /System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/plat-darwin /System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/plat-mac /System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/plat-mac/lib-scriptpackages /System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python /System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-tk /System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-old /System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-dynload /Library/Python/2.6/site-packages /System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/PyObjC /System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/wx-2.8-mac-unicode I welcome any criticism and comments, if any of the above looks foolish or poorly conceived. I'm new to all of this. Thanks! Running OSX 10.6.5 on a MacBook Pro, invoking python 2.6.1 from Terminal

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• Cannot set ILMerge path to console

  - by KMC

  I install ILMerge.exe; path is C:\Program Files\Microsoft\ILMerge\ILMerge.exe. I want to set the command to the Path so I can type ilmerge anywhere to use the application. I googled and tried all the following but none works: setx -m ilmerge;C:\Program Files\Microsoft\ILMerge\ILMerge.exe setx -M ilmerge;C:\Program Files\Microsoft\ILMerge\ILMerge.exe setx -m %PATH%;C:\Program Files\Microsoft\ILMerge\ILMerge.exe setx /S system /U administrator ilmerge;C:\Program Files\Microsoft\ILMerge\ILMerge.exe I then tried to add, the GUI's Environment Variables, click New and input the variable "ilmerge" and value "C:\Program Files\Microsoft\ILMerge\ILMerge.exe". But in command prompt and type in ilmerge, still gives me 'ilmerge' is not recognized as an internal or external command, operable program or bath file. Why something as basic as setting a path that confusing..

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• Make PATH variable changes permanent on openSuse

  - by Marlon

  Okay, so I'm trying to do something that should be rather simple but for some reason I can't quite seem to make it work. All I simply want to do is add a path to the PATH environment variable in openSuse. So far, I've edited the following line in /etc/default/su : PATH=/usr/local/bin:/bin:/usr/bin with this line : PATH=/usr/local/bin:/bin:/usr/bin:/usr/local/php/bin:/usr/local/mysql/bin Basically, all I want to do is have access to php and mysqld regardless of how I log in directly from the command prompt without having to type trailing /usr/local/php/bin/ every time. Am I even editing the right file? I'm a bit of a Linux newbie and to achieve something as trivial as this is eluding me. Server gods out there, drop be a crumb, please? :-)

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• Python version priority in OSX/UNIX PATH environment variable

  - by mindthief

  Hi all, I want my system to use /usr/bin/python, but it's currently using /opt/local/bin/python, which points to /usr/bin/python2.6. I tried modifying the PATH variable in my .bashrc as PATH=~/bin:$PATH ...and then set a symbolic link in ~/bin to point to /usr/bin/python. i.e. ~/bin/python --> /usr/bin/python I figured this might prioritize this symlink over the /opt/local version if it came before the other one in the PATH variable, but when I opened a new shell I still found python pointing to /opt/local/bin. Any advice on a good way to get the system to use /usr/bin/python? Also, I usually use ipython as opposed to python directly. I'm assuming that if the system starts to use the correct version of python then ipython would also use that version? If not, how could I also get ipython to use the correct version? Thanks!

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• How to copy files from shadow copy with long source path

  - by Jake

  The files and folders in my shared network drive (set up with DFS) were mass deleted. Currently I am trying to recover the files from the shadow copy "Previous Version". Problem is, thousands of files are deeply nested with long paths making the file path too long. When copying, it shows the dialog "Source Path Too Long". My guess is that the file path just barely hits the limit when saved into the network drive, but shadaw copy service appends the date and time to the folders so the path character limit is exceeded. How else can I copy the files from shadow copy?

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• Modify PATH variable for X11 during log-in

  - by user1028435

  I am working on some lab computers (read: no administrative rights) that, if I log in, I need to change the PATH variable as X11 starts. The reason is that I need to change the PATH variable at this time, as opposed to later, is that the Print Screen command seems to "bind" during login (forgive my bad explanation of this). Currently, I have a .bashrc script as a workaround: #!/bin/bash export PATH=/home/username/bin:$PATH I can make it work by starting a new X, but I was wondering if it is possible to change upon login. cat /etc/redhat-release tells me my distribution is: Red Hat Enterprise Linux Client release 5.8 (Tikanga)

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• What does "/" , "./", "../" represent while giving path?

  - by q234e

  What does "/" , "./", "../" represent while giving path?

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• Windows 7 - User-specific %PATH%

  - by MiffTheFox

  I'd like to set up a system for Windows 7 where each user has their own private directory in %PATH%. I tried setting %PATH% to %HOMEDRIVE%%HOMEPATH%\Bin;%SystemRoot%\System32;[...] but it doesn't seem to work. For those who don't realize what I'm trying to do, it's sort of like EXPORT PATH=~/bin would be on *nix. It can be on a user specific basis if need be (and that would actually be prefer to the machine-wide settings).

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• SQL SERVER – Solution – 2 T-SQL Puzzles – Display Star and Shortest Code to Display 1

  - by pinaldave

  Earlier on this blog we had asked two puzzles. The response from all of you is nothing but Amazing. I have received 350+ responses. Many are valid and many were indeed something I had not thought about it. I strongly suggest you read all the puzzles and their answers here - trust me if you start reading the comments you will not stop till you read every single comment. Seriously trust me on it. Personally I have learned a lot from it. Let us recap the puzzles here quickly. Puzzle 1: Why following code when executed in SSMS displays result as a * (Star)? SELECT CAST(634 AS VARCHAR(2)) Puzzle 2: Write the shortest code that produces results as 1 without using any numbers in the select statement. Bonus Q: How many different Operating System (OS) NuoDB support? As I mentioned earlier the participation was nothing but Amazing. I will write about the winners and the best answers in short time. Meanwhile I will give to the point answers to above puzzles. Solution 1: When you convert character or binary expressions (char, nchar, nvarchar, varchar,binary, or varbinary) to an expression of a different data type, data can be truncated, only partially displayed, or an error is returned because the result is too short to display. Conversions to char, varchar, nchar, nvarchar, binary, and varbinary are truncated, except for the conversions shown in the following table. Reference of the text and table from MSDN. Solution 2: The shortest code to produce answer 1 : SELECT EXP($) or SELECT COS($) or SELECT DAY($) When SELECT $ it gives us the result as 0.00 and the EXP of the same is 1. I believe it is pretty neat. There were plenty other answers but this was the shortest. Another shorter answer would be PRINT EXP($) but no one has proposed that as in original Question I have explicitly mentioned SELECT in the original question. Bonus Answer: 5 OS: Windows, MacOS, Linux, Solaris, Joyent SmartOS Reference Please do read every single comment here. Do leave a comment which one do you think is the best comment out of all the comments. Meanwhile if there is a better solution and I have missed it do let me know as we still have time to correct it. I will be selecting the winner before the weekend as I am going through each and every of 350 comment. I will be selecting the best comments along with the winning comment. If our selection matches – one of you may still win something cool.  Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology Tagged: NuoDB

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• Could I do this blind relative to absolute path conversion (for perforce depot paths) better?

  - by wonderfulthunk

  I need to "blindly" (i.e. without access to the filesystem, in this case the source control server) convert some relative paths to absolute paths. So I'm playing with dotdots and indices. For those that are curious I have a log file produced by someone else's tool that sometimes outputs relative paths, and for performance reasons I don't want to access the source control server where the paths are located to check if they're valid and more easily convert them to their absolute path equivalents. I've gone through a number of (probably foolish) iterations trying to get it to work - mostly a few variations of iterating over the array of folders and trying delete_at(index) and delete_at(index-1) but my index kept incrementing while I was deleting elements of the array out from under myself, which didn't work for cases with multiple dotdots. Any tips on improving it in general or specifically the lack of non-consecutive dotdot support would be welcome. Currently this is working with my limited examples, but I think it could be improved. It can't handle non-consecutive '..' directories, and I am probably doing a lot of wasteful (and error-prone) things that I probably don't need to do because I'm a bit of a hack. I've found a lot of examples of converting other types of relative paths using other languages, but none of them seemed to fit my situation. These are my example paths that I need to convert, from: //depot/foo/../bar/single.c //depot/foo/docs/../../other/double.c //depot/foo/usr/bin/../../../else/more/triple.c to: //depot/bar/single.c //depot/other/double.c //depot/else/more/triple.c And my script: begin paths = File.open(ARGV[0]).readlines puts(paths) new_paths = Array.new paths.each { |path| folders = path.split('/') if ( folders.include?('..') ) num_dotdots = 0 first_dotdot = folders.index('..') last_dotdot = folders.rindex('..') folders.each { |item| if ( item == '..' ) num_dotdots += 1 end } if ( first_dotdot and ( num_dotdots > 0 ) ) # this might be redundant? folders.slice!(first_dotdot - num_dotdots..last_dotdot) # dependent on consecutive dotdots only end end folders.map! { |elem| if ( elem !~ /\n/ ) elem = elem + '/' else elem = elem end } new_paths << folders.to_s } puts(new_paths) end

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• Python os.path.join on Windows

  - by Jim

  I am trying to learn python and am making a program that will output a script. I want to use os.path.join, but am pretty confused. According to the docs if I say: os.path.join('c:', 'sourcedir') I get "C:sourcedir". According to the docs, this is normal, right? But when I use the copytree command, Python will output it the desired way, for example: import shutil src = os.path.join('c:', 'src') dst = os.path.join('c':', 'dst') shutil.copytree(src, dst) Here is the error code I get: WindowsError: [Error 3] The system cannot find the path specified: 'C:src/*.*' If I wrap the os.path.join with os.path.normpath I get the same error. If this os.path.join can't be used this way, then I am confused as to its purpose. According to the pages suggested by Stack Overflow, slashes should not be used in join—that is correct, I assume?

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• Optimizing Dijkstra for dense graph?

  - by Jason

  Is there another way to calculate the shortest path for a near complete graph other than Dijkstra? I have about 8,000 nodes and about 18 million edges. I've gone through the thread "a to b on map" and decided to use Dijkstra. I wrote my script in Perl using the Boost::Graph library. But the result isn't what I expected. It took about 10+ minutes to calculate one shortest path using the call $graph-dijkstra_shortest_path($start_node,$end_node); I understand there are a lot of edges and it may be the reason behind the slow running time. Am I dead in the water? Is there any other way to speed this up?

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• How to find full module path of a class to import in other file

  - by Pooya

  I have method that returns module path of given class name def findModulePath(path, className): attributes = [] for root, dirs, files in os.walk(path): for source in (s for s in files if s.endswith(".py")): name = os.path.splitext(os.path.basename(source))[0] full_name = os.path.splitext(source)[0].replace(os.path.sep, '.') m = imp.load_module(full_name, *imp.find_module(name, [root])) try: attr = getattr(m, className) attributes.append(attr) except: pass if len(attributes) <= 0: raise Exception, "Class %s not found" % className for element in attributes: print "%s.%s" % (element.__module__, className) but it does not return the full path of the module, For example I have a python file named "objectmodel" in objects package,and it contains a Model class, So I call findModulePath(MyProjectPath,"Model"). it prints objectmodel.Model but I need objects.objectmodel.Model

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• Getting a partial path to a file in a bash script

  - by Massif

  I have a path that is stored in a variable $FULLPATH="/this/is/the/path/to/my/file.txt" I also have another variable containing a partial path $PARTIAL="/this/is/the/" I want to remove the partial path from the full path so that I am left with: path/to/my/file.txt What's the best way to do this?

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• sendmail is using return-path instead of from address

  - by magd1

  I have a customer that is complaining about emails marked as spam. I'm looking at the header. It shows the correct From: [email protected] However, it doesn't like the return-path. Return-Path: <[email protected]> Received-SPF: neutral (google.com: x.x.x.x is neither permitted nor denied by domain of [email protected]) client-ip=x.x.x.x; Authentication-Results: mx.google.com; spf=neutral (google.com: x.x.x.x is neither permitted nor denied by domain of [email protected]) [email protected] How do I configure sendmail to use the From address for the Return-Path?

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• 32-bit java dominates my PATH magically

  - by Kos

  I have a 32-bit Java installed just for Chrome and 64-bit Java JDK for everything else. When I type java -version in the cmd, the 32-bit Java answers: C:\>java -version java version "1.6.0_26" Java(TM) SE Runtime Environment (build 1.6.0_26-b03) Java HotSpot(TM) Client VM (build 20.1-b02, mixed mode, sharing) This is the 32-bit JRE installed for Chrome (the installer name was chromeinstall.exe). However, I'd like the default Java to be this one: C:\>"Program Files\Java\jre6\bin\java.exe" -version java version "1.6.0_26" Java(TM) SE Runtime Environment (build 1.6.0_26-b03) Java HotSpot(TM) 64-Bit Server VM (build 20.1-b02, mixed mode) And for the fun part, only the 64-bit one is in PATH! C:\>echo %PATH% C:\Windows\system32;C:\Program Files\Java\jre6\bin (snipped irrelevant entries) So long story short: 64-bit JRE is in PATH, but 32-bit JRE is ran by default. What is happening here? How to fix it? Tried reinstalling the 64-bit JDK as a whole, didn't help.

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• Changing path to basedir of mysql

  - by shantanuo

  When-ever I need to start mysql from command line, I need to cd to the base directory and then use mysql command as shown below: # cd /home/ec2-user/percona-5.5.30-tokudb-7.0.1-fedora-x86_64/ # ./bin/mysql Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 3 mysql> How do I start mysql simply by typing "mysql" at command prompt? I tried to export the path but it did not work. export path=$PATH:/home/ec2-user/percona-5.5.30-tokudb-7.0.1-fedora-x86_64/bin/

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• Mac OS X 10.6 executable not found without full path

  - by Danack

  I just installed Apache via MacPorts. It seems that my Mac was absolutely confused about which version of the Apache executables to run. After moving the Apache executables that ship with the Mac to a directory that is not listed in the PATH variable, trying to run the httpd built by MacPorts fails even though the correct directory (/opt/local/apache2/bin) is listed in the PATH variable. If I navigate to the directory /opt/local/apache2/bin and type the command httpd I still get the error message -bash: httpd: command not found If I type the command with the full path /opt/local/apache2/bin/httpd it works fine. I've run the command alias to see if something was clashing but the only thing listed is: alias wget='curl -O' How do I find what is intercepting the command and preventing the executable being found in the directory, even when I'm inside the same directory? By the way, the httpd file is executable: -rwxr-xr-x 1 root admin 442496 9 May 2012 httpd

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• Windows 7 PATH not expanding

  - by trinithis

  I am using the following to create and edit environment variables for Windows 7. Control Panel\All Control Panel Items\System -> Advanced system settings -> Environment Variables Under System variables I have the following pertinant variables: PROG32=C:\Program Files (x86) REALDWG_SDK_DIR=%PROG32%\Autodesk\RealDWG 2011 Path=%REALDWG_SDK_DIR%;%PROG32%\Haskell\bin However, the following happens: C:\>echo %PROG32% C:\Program Files (x86) C:\>echo %Path% %REALDWG_SDK_DIR%;C:\Program Files (x86)\Haskell\bin Is it possible to have a chain of variables expand? If I rename Path to something else, I sometimes get the problem, and sometimes I don't.

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• PATH env variable on Mac OS X and/or Eclipse

  - by Jason S

  When I print out the path in bash, it prints this: /usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin When I run System.out.println(System.getenv("PATH")); in Java running under Eclipse, it prints /usr/bin:/bin:/usr/sbin:/sbin How can I figure out why there is this discrepancy? I need to add /usr/local/bin to the PATH and make it available to Java apps under Eclipse. (note: I have made no modifications system paths, so these are the defaults set by the OS or perhaps by one or more of the applications i've installed.)

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• Path erased in Debian

  - by Lyon83

  I'm trying to deploy a rails app in Debian, using Apache/Passenger. I was trying to fox a problem with some GEMs and in the process I put executed this in console: export PATH=/var/lib/gems/1.8/bin/:${vendor/cache} Now my path environmental variable is gone, or at least its content. My server is running under Debian 6. Is there a way to recover my path info? Or at least can someone point me where to find the file where that variable i s stored? Some help please. This is a BIG problem for me. Thanks in advance!

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