I'd like to install openCV to vectorize image, but there's a series error message regarding Xcode and Ruby.
First, I use terminal to install openCV, brew install opencv.
Then, I got error message indicating that the system doesn't like my ruby version.
/usr/local/Homebrew/Library/Homebrew/brew.rb:12:in `<main>':
Homebrew must be run under Ruby 2.3! You're running 2.0.0. (RuntimeError)
So, I want to upgrade my ruby. I followed several update strategy from this post. First ruby upgrade trial: brew link --overwrite ruby & brew unlink ruby && brew link ruby and get
Error: No such keg: /usr/local/Cellar/ruby
Then second ruby upgrade trial: brew upgrade ruby and see the following error message.
Error: Xcode alone is not sufficient on Sierra.
Install the Command Line Tools:
xcode-select --install
This error message means I need to install Xcode which I already install. So, I check my Xcode status with code-select -p and get /Applications/Xcode.app/Contents/Developer which means I am fine.
I saw a comment regarding where you install python could be a big issue. Quote from the source:
If you see /usr/local/bin/python3 then you are correctly using the Homebrew version of Python. If the output is instead /usr/bin/python3 then you are incorrectly using the system version of Python.
I check which python3 and get
/Users/******/anaconda3/bin/python3
Could this be the problem? How can I change system version to local?
Let me explain this myself so people won't make the same mistakes.
When I saw the last line of the error message
Error: Xcode alone is not sufficient on Sierra.
Install the Command Line Tools:
xcode-select --install
My thought was: I already have Xcode why the system ask me to "reinstall" it. However, thanks for #SamiKuhmonen # Beartech #patrick kuang suggestion, I search a page (in Mandarin). xcode-select --install does not reinstall the whole Xcode. It means install some missing command line tools which is required by installing Ruby.
Trying to install k8s package via brew , I just got the same issue a while ago saying in the terminal :
Error: Xcode alone is not sufficient on Sierra.
Install the Command
Line Tools: xcode-select --install
You need to download *.dmg file; named Command Line Tools (macOS x.x.x) for XCode N . Search on it here : https://developer.apple.com/download/more/ . You must have developer account.
Then, congrats! 🎉
update for 2019
macOS Mojave 10.14.5
Use Xcode10.2 for macOS 10.14
I had the same issue in my Macbook Pro on Sierra. Apart from updating Xcode from the App Store, I also installed the command line utilities using the xcode-select --install command.
After the update steps, brew commands started working fine. I also updating my OS during this time.
I got the same message despite having Xcode and the command line tools already being installed a long time ago and updated numerous times.
I think it is the Apple way of telling you that Xcode command line tools need to be updated, as the App Store showed me the below:
After executing the xcode-select --install command, the update disappears from the App Store, which means they are exactly the same thing.
I had the same problem. I installed 'Command Line Tools for XCode' (choose appropriate version) from https://developer.apple.com/download/more/ and restarted my terminal. Issue resolved :)
Related
I am trying to update Xcode from the command line. Initially I tried running:
xcode-select --install
which resulted in this message:
xcode-select: error: command line tools are already installed, use "Software Update" to install updates
So the question remains, is there a way to update Xcode from the command line?
What you are actually using is the command to install the Xcode command line tools - xcode-select --install. Hence the error message you got - the tools are already installed.
The command you need to update Xcode is softwareupdate command [args ...]. You can use softwareupdate --list to see what's available and then softwareupdate --install -a to install all updates or softwareupdate --install <product name> to install just the Xcode update (if available). You can get the name from the list command.
As it was mentioned in the comments here is the man page for the softwareupdate tool.
2019 Update
A lot of users are experiencing problems where softwareupdate --install -a will in fact not update to the newest version of Xcode. The cause for this is more than likely a pending macOS update (as #brianlmerritt pointed out below). In most cases updating macOS first will solve the problem and allow Xcode to be updated as well.
Updating the Xcode Command Line Tools
A large portion of users are landing on this answer in an attempt to update the Xcode Command Line Tools. The easiest way to achieve this is by removing the old version of the tools, and installing the new one.
sudo rm -rf /Library/Developer/CommandLineTools
xcode-select --install
A popup will appear and guide you through the rest of the process.
I had the same issue and I solved by doing the following:
removing the old tools ($ sudo rm -rf /Library/Developer/CommandLineTools)
install xcode command line tools again ($ xcode-select --install).
After these steps you will see a pop to install the new version of the tools.
I encountered the same issue when I uninstalled the complete version of Xcode to reinstall the CLI version. My fix was:
sudo xcode-select -s /Library/Developer/CommandLineTools
After installing Command Line Tools (with xcode-select --install), type:
sudo xcode-select --switch /Library/Developer/CommandLineTools/
You should be able to run git now:
10:29 $ git --version
git version 2.17.2 (Apple Git-113)
I got this error after deleting Xcode. I fixed it by resetting the command line tools path with sudo xcode-select -r.
Before:
navin#Radiant ~$ /usr/bin/clang
xcrun: error: active developer path ("/Applications/Xcode.app/Contents/Developer") does not exist
Use `sudo xcode-select --switch path/to/Xcode.app` to specify the Xcode that you wish to use for command line developer tools, or use `xcode-select --install` to install the standalone command line developer tools.
See `man xcode-select` for more details.
navin#Radiant ~$ xcode-select --install
xcode-select: error: command line tools are already installed, use "Software Update" to install updates
After:
navin#Radiant ~$ /usr/bin/clang
clang: error: no input files
Just type the commands
cd /Library/Developer/CommandLineTools/Packages/;
open macOS_SDK_headers_for_macOS_10.14.pkg
Reference: https://forums.developer.apple.com/thread/104296
$ sudo rm -rf /Library/Developer/CommandLineTools
$ xcode-select --install
I was facing the same problem, resolved it by using the following command.
sudo xcode-select -s /Library/Developer/CommandLineTools
After running the above command then xcode-select -p command showed the following.
/Library/Developer/CommandLineTools
#Vel Genov's answer is correct, except when the version of Xcode can't be updated because it is the latest version for your current version of Mac OS. If you know there is a newer Xcode (for example, it won't load an app onto a device with a recent version of iOS) then it's necessary to first upgrade Mac OS.
Further note for those like me with old Mac Pro 5.1. Upgrading to Mojave required installing the metal gpu (Sapphire AMD Radeon RX 560 in my case) but make sure only HDMI monitor is installed (not 4K! 1080 only). Only then did install Mojave say firmware update required and shut computer down. Long 2 minute power button hold and it all upgraded fine after that!
Catalina update - softwareupdate --install -a won't upgrade xcode from command line if there is a pending update (say you selected update xcode overnight)
I am not sure why this was so tricky for me.
sudo xcode-select --install
Did nothing for me.
softwareupdate --all --install --force
Did nothing for me.
I had to do things in the following order
sudo rm -rf /Library/Developer/CommandLineTools
sudo xcode-select --install
This installed a newer xcode, but not latest.
Then I did
softwareupdate --all --install --force
and they updated completely.
Xcode::Install is a simple cli software that allow you to install/select a specific Xcode version.
You can install it using gem install xcode-install
Then you will be able to install a specific version with xcversion install 9.4.1
And if you have more than one version installed, you can switch version with xcversion select 9.4
You can find more information at https://github.com/KrauseFx/xcode-install
I am now running OS Big Sur. xcode-select --install, and sudo xcode-select --reset did not resolve my issue, neither did the recommended subsequent softwareupdate --install -a command. For good measure, I tried the recommended download from Apple Downloads, but the Command Line Tools downloads available there are not compatible with my OS.
I upvoted the fix that resolved for me, sudo xcode-select --switch /Library/Developer/CommandLineTools/ and added this post for environment context.
I was able to update via CLI using:
softwareupdate --list --verbose
and then
softwareupdate -i Command\ Line\ Tools\ for\ Xcode-13.2
I was trying to use the React-Native Expo app with create-react-native-app but for some reason it would launch my simulator and just hang without loading the app. The above answer by ipinak above reset the Xcode CLI tools because attempting to update to most recent Xcode CLI was not working. the two commands are:
rm -rf /Library/Developer/CommandLineTools
xcode-select --install
This process take time because of the download.
I am leaving this here for any other would be searches for this specific React-Native Expo fix.
I was faced with this today after an update from Xcode (App Store on Mac) updated my Xcode.
My SourceTree wouldn't allow me to do a merge conflict.
In Xcode I found that Command Tools was NOT selected.
I selected it, however still no dice as I was getting the same message of:
I performed the command:
softwareupdate --list
which gave me a list of products, including THREE (3) versions of CommandLine Tools
Software Update Tool
Finding available software
Software Update found the following new or updated software:
Label: Command Line Tools for Xcode-13.2
Title: Command Line Tools for Xcode, Version: 13.2, Size: 577329K, Recommended: YES,
Label: SFSymbolsAuto-3.3
Title: SF Symbols, Version: 3.3, Size: 169368K, Recommended: YES,
Label: Command Line Tools for Xcode-13.3
Title: Command Line Tools for Xcode, Version: 13.3, Size: 718145K, Recommended: YES,
Label: Command Line Tools for Xcode-13.4
Title: Command Line Tools for Xcode, Version: 13.4, Size: 705462K, Recommended: YES,
my version of Xcode is 13.4, so I preceded to try to update just the one.
I used the Label, with escaped spaces (which also works with just quoted label btw "Command Line Tools for Xcode-13.4"
softwareupdate -i Command\ Line\ Tools\ for\ Xcode-13.4
In doing so, ALL 3 updates of Command Line Tools disappeared and I was able to continue.
Hope this helps someone else out there.
Hello I solved it like this:
Install Application> Xcode.app> Contents> Resources> Packages> XcodeSystemResources.pkg.
I arrived here trying to install Appium. Adding my answer in case other folks land here for the same issue.
appium-doctor --ios
... bunch of stuff...
WARN AppiumDoctor ✖ Error running xcrun simctl
... bunch of stuff...
info AppiumDoctor ### Manual Fixes Needed ###
info AppiumDoctor The configuration cannot be automatically fixed, please do the
following first:
WARN AppiumDoctor ➜ Manually install Xcode, and make sure 'xcode-select -p' command shows proper path like '/Applications/Xcode.app/Contents/Developer'
In my case
xcode-select -p
/Library/Developer/CommandLineTools
which appeared wrong...but I knew I had recently updated Xcode and the command line tools
so...
sudo xcode-select -r (sudo required)
then...
xcode-select -p
/Applications/Xcode.app/Contents/Developer
After this, no warning. Appium-doctor returned clean.
xCode version 11.2.1 is necessary for building app in iPad 13.2.3, When I directly try to upgrade from xcode 11.1 to 11.2.1 through App Store it get struck, So after some research , I found a solution to upgrade by removing the existing xcode from the system
So here I am adding the steps to upgrade after uninstalling existing xcode.
Go to Applications and identify Xcode and drag it to trash.
Empty trash to permenently delete Xcode.
Now go to ~/Library/Developer/ folder and remove the contents completely Use sudo rm -rf ~/Library/Developer/ to avoid any
permission issue while deleting
Lastly remove any cache directory associated with xcode in the path ~/Library/Caches/com.apple.dt.Xcode sudo rm -rf
~/Library/Caches/com.apple.dt.Xcode/*
After completing the above steps you can easly install xcode from App Store, which will install the current latest version of xcode
Note: Please take a backup of your existing projects before making the above changes
Update with this one-liner.
softwareupdate --install -a
This reminds me why I hate MacOS. Every time I tried one of these errors I would get the incomprehensible error: No install could be requested (perhaps no UI is present)
Turns out this "CLI" actually needs a graphical session to run. WTF! Very useful when you're actually only ever connecting to the remote mac server over SSH to queue iOS builds.
So the answer for me was:
Physically travel to the Mac, attach screen, mouse and keyboard, and run the command there.
To those having this issue after update to Catalina, just execute this command on your terminal
sudo rm -rf /Library/Developer/CommandLineTools; xcode-select --install;
I have been trying to instal the Git on my mac, But every time I use the command $git --version.
I get the following error
xcrun: error: active developer path ("/Volumes/Xcode/Xcode.app/Contents/Developer") does not exist, use xcode-select --switch path/to/Xcode.app to specify the Xcode that you wish to use for command line developer tools (or see man xcode-select)
I have already installed the Xcode on my mac for iOS App development.
I am not sure what this error is trying to say.
My case:
I removed XCode. JetBrains integration with git - breaks. Found this error in terminal.
My soltuion:
I don't want to download XCode to restore PyCharm. So I ran:
sudo xcode-select --reset
So from discussion in the comments above, it seems the right fix here is just to run the command /usr/bin/xcode-select -switch once (i.e., run it with the full path to the executable, rather than just as xcode-select) with /Applications/Xcode.app/Contents/Developer/ as the argument:
sudo /usr/bin/xcode-select -switch /Applications/Xcode.app/Contents/Developer
After running that once, everything should work as expected from then on.
sudo /usr/bin/xcode-select --switch /Library/Developer/CommandLineTools
and reboot your computer.
Try this below answer. It's worked for me.
Open your Xcode Preferences,
--> Select Locations
--> Select your specific Xcode version in Command Line Tools
It was easier for me to let Xcode pick the install location of Command Line Tools for me, instead of the other way around. After downloading the .xip file from the Apple Developer downloads page, expanding the compressed contents, and installing Xcode.App, I was able to open it using Spotlight.
And open preferences:
And select my Command Line Tools under "Locations".
You can install git via the brew package manager for Mac. I recommend installing software this way since it's a great way to manage your installed packages in one place. For example, you can do brew update to get a list of the latest package updates, or brew upgrade to upgrade all of your software installed through brew.
To install brew, open a terminal window and run:
ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
Update your brew packages with brew update
Install git with brew install git
I had installed git, then returned to a terminal window open prior to the installation. I try running command git --version and this raised error message below. To resolve, I ran command source /etc/profile in same terminal window. BTW, terminal window is inside my Webstorm and my end goal is to git init and setup git for my new reactjs project. Happy coding!
The error:
xcrun: error: active developer path ("/Volumes/Xcode/Xcode.app/Contents/Developer") does not exist, use \`xcode-select --switch path/to/Xcode.app\` to specify the Xcode that you wish to use for command line developer tools (or see \`man xcode-select\`)
I'm trying to install and use Cocoapods with Xcode. I've installed already Brew, so I've used this command:
sudo gem install cocoapods
but it stays there, without response and without asking me for password (that's really strange, because of sudo command).
Maybe I got some problem with Brew Installation or Ruby on my Yosemite iMac?
I met the same error in the past, there is something wrong with my development environment. I re-install the Command Line Tools follow this guide, then everything is ok.
You can get the detail information from here, hope it can help you.
I have problems with my macport after update to OS X 10.9.
I try to follow this manual https://trac.macports.org/wiki/Migration to fix them.
But when I install Command Line Tools:
xcode-select --install
I get message
Can't install the software because it is not currently available from
the Software Update server.
Meanwhile I successfully updated my other machine to OS X 10.9. and installed command-line tools with no problems, so they must be available.
What is the problem here?
You can download the command line tools for OS X Mavericks manually from here:
https://developer.apple.com/downloads/index.action?name=for%20Xcode
For OSX 10.11 or more you can download from here https://developer.apple.com/download/more/.
(The link in the accepted answer doesn't display command line tools for El Capitan (OSX 10.11))
If you are trying this on a latest Mac OS X Mavericks, command line tools come with the Xcode 5.x
So make sure you have installed & updated Xcode to latest
after which make sure Xcode command line tools is pointed correctly using this command
xcode-select -p
Which might show some path like
/Applications/Xcode.app/Contents/Developer
Change the path to correct path using the switch command:
sudo xcode-select --switch /Library/Developer/CommandLineTools/
this should help you set it to correct path, after which you can use the same above command -p to check if it is set correctly
I faced same problem of Can't install the software because it is currently not available from the Software Update Server. You may try following steps instead to make the Software Update initiate update for the Command Line Tools.
Check if Command Line Tools Update is mentioned in your list of softwares to be updated by using following command: softwareupdate -l
If Command Line Tools Update is not mentioned in that list, then manually make it part of the list using following command which will create a temporary file: sudo touch /tmp/.com.apple.dt.CommandLineTools.installondemand.in-progress
Verify that the list now has the Command Line Tools mentioned by running softwareupdate -l again.
Now, press Cmd+Space to initiate Mac's Spotlight Search. Search for Software Update. Start the Software Update.
That will show you following kind of dialog for installing the Command Line Tools. Install away the update and be merry. :)
Remove the temporary file created in Step 2: sudo rm /tmp/.com.apple.dt.CommandLineTools.installondemand.in-progress.
I deleted the command tools directory given by xcode-select -p due to npm gyp error.
xcode-select failed to install the files with the not available error.
I ran the Xcode application and the command tools installed as part of the startup.
npm worked.
However this didn't fully fix the tools. I had to use xcode-select to switch the path to the Developer directory within the Xcode application directory.
sudo xcode-select --switch /Applications/Xcode.app/Contents/Developer
MacOS catalina.
I just got the same error after I upgraded to 10.14 Mojave and had to reinstall command line tools (I don't use the full Xcode IDE and wanted command line tools a la carte).
My xcode-select -p path was right, per Basav's answer, so that wasn't the issue.
I also ran sudo softwareupdate --clear-catalog per Lambda W's answer and that reset to Apple Production, but did not make a difference.
What worked was User 92's answer to visit https://developer.apple.com/download/more/.
From there I was able to download a .dmg file that had a GUI installer wizard for command line tools :)
I installed that, then I restarted terminal and everything was back to normal.
I know this is an old post but I also ran into this problem today. I found out that when I executed sudo softwareupdate -l the Command Line Tools were listed as an update, so I installed them using sudo softwareupdate -i -a.
This error can occur if you are using a software update server which doesn't host the required package.
You can check this by running
defaults read /Library/Preferences/com.apple.SoftwareUpdate
and seeing if you have an entry called CatalogURL or AppleCatalogURL
You can point back at the Apple software update server by either removing this entry or using the command
sudo softwareupdate --clear-catalog
And then run the command line tools install again.
I got the same issue on MacOS Catalina.
I think I identified the root cause: I have switched the default Apple ID account and the new one was not activated as a Developer account. When I ran the xcode-select --install command, I got the same error as stated in the issue description.
After reading this post on stackoverflow, I went on https://developer.apple.com/downloads and I was asked to accept Developers terms. I think it enabled my account as a developer one. Then, I tried to run xcode-select --install again and it worked.
The command
xcode-select --install
proposes 3 options: Get Xcode; Not Now; Install.
When I choose to get full Xcode the command finished successfully. It took a while, but this way I was able to complete all macports migration instructions.
Once you get the command line tools loaded as described by Nikos M in his excellent answer above you will need to agree to the gcc license and if you are using ruby gems you may need to link llvm-gcc as gcc-4.2.
If you do not do these the gem install will report "You have to install development tools first." after you have already installed them.
The steps are:
sudo gcc
sudo ln -s /usr/bin/llvm-gcc /usr/bin/gcc-4.2
The gcc must be run once under sudo so Apple can update their license info, you don't need an input file, it will update the license before it checks its arguments. The link is needed so that ruby 1.9 can find the compiler when building certain gems, such as the debugger. This may be fixed in ruby 2.x, but I'll cross that bridge when I get there.
I had to run Xcode.app and agree to the License Agreement
Setup: Brand new MacBook with Mavericks, then brew install and other c/l type things 'just work'.
I solved this by going to the App Store and installing Xcode.
It was a pretty large 11GB install, so this is probably overkill. But, as a last resort, it seems to have solve my issues. In the middle of the installation (well around 10GB), Mac OS told me there was an update to Command Line Tools for Xcode. Performing this installation won't fix anything until Xcode is fully installed.
Once the install is done, it should start working (after you accept the license agreement).
Command + Space
Search for Xcode
Open it and accept license
Then run again from terminal xcode-select --install
Had the same issue and was getting the same error. When i ran xcode-select -p, it gave output as /Library/Developer/CommandLineTools. So that means xcode was already installed in my system. Then i ran steps as given on this answer. After which any command which required xcode ran successfully.
I am having trouble getting MacPorts to function properly. I just installed OSX Lion 10.7.3 I downloaded and installed MacPorts first, and then after reading the requirements, I downloaded Xcode4.3 from the App Store, and then installed it. I launched Xcode and it looks to be operational and functional. However when I attempted to port with MacPorts, it gave me this error message(excerpt):
Warning: xcodebuild exists but failed to execute
Warning: Xcode does not appear to be installed; most ports will likely fail to build.
I followed the advice from:
How do i install additional packages for Xcode on OSX Lion to allow MacPorts to work
and installed command_line_tools_for_xcode from the Preferences within Xcode. I closed Xcode, and again got the errors:
$ sudo port install libsocketsPassword:
Warning: xcodebuild exists but failed to execute
Warning: Xcode does not appear to be installed; most ports will likely fail to build.
---> Computing dependencies for libsockets
---> Dependencies to be installed: openssl zlib
---> Extracting zlib
Error: Couldn't determine your Xcode version (from '/usr/bin/xcodebuild -version').
Error:
Error: If you have not installed Xcode, install it now; see:
Error: http://guide.macports.org/chunked/installing.xcode.html
Error:
Error: Target org.macports.extract returned: unable to find Xcode
Error: Failed to install zlib
Log for zlib is at: /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_archivers_zlib/zlib/main.log
Error: The following dependencies were not installed: openssl zlib
Error: Status 1 encountered during processing.
I am uncertain where to go next with this. How do i trouble shoot my Xcode and MacPort interface?
In theory this should work if you have Xcode4.3 installed (in /Applications):
$ sudo xcode-select -switch /Applications/Xcode.app/Contents/Developer/
(And you've installed the optional command line tools)
Everything will start working fine after installation of "Command Line Tools for Xcode" package.
You can get it from here: https://developer.apple.com/downloads/index.action#
Please see the MacPorts migration instructions for Xcode 4.3.
The instructions are pretty involved. You need to run xcode-select to set a new tools path, update developer_dir in macports.conf (as described by Henk Poley), re-install MacPorts (ouch), and finally uninstall and re-install all of your ports (double ouch).
Edit: libpvx still wouldn't install after the above. Two extra steps were required:
sudo ln -s /Developer /
sudo ln -s /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs /SDKs
YMMV if you have different ports installed!
Also in /opt/local/etc/macports/macports.conf change the line with developer_dir to point to / instead of /Developer.
After
sudo xcode-select -switch /Applications/Xcode.app
I also had to run
sudo xcodebuild -license
and accept the licence
Here is a solution that has worked for me:
Install Command Line Tools for Xcode
Xcode -> Preferences -> Downloads
Help MacPorts find the right Xcode folder
sudo /usr/bin/xcode-select -switch /Applications/Xcode.app
Create symbolic links for clang compilers as they now live elsewhere
sudo ln -s `which clang` /Applications/Xcode.app/Contents/Developer/usr/bin/
sudo ln -s `which clang++` /Applications/Xcode.app/Contents/Developer/usr/bin/
Try using trunk, there's no release supporting Xcode 4.3 yet.
Setting the developer path in /opt/local/etc/macports.conf works for me,
developer_dir /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain
since most of the compilers are stored there now instead of /usr/bin under Developer.
None of this works for me. Wait for macports to release a new version that officially supports XCode 4.3+
sudo mv /usr/bin/xcodebuild /usr/bin/xcodebuild.old
sudo ln -s /Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild /usr/bin/xcodebuild
Starting with Xcode 4.3, the command-line build tools are not installed by default. Launch Xcode, open the Preferences, and go to the Downloads tab. From there you should have an option to install the command-line tools.
You can also download them from the web here: https://developer.apple.com/downloads/index.action
Disclaimer: I haven't installed Xcode 4.3 yet. I have only read about it on the web.
As of 27/2/2012, the official suggestion from MacPorts seems to be to not use XCode 4.3 and instead use 4.1 through 4.2.1, which can be downloaded from Apple.
There is a bug ticket which might be useful to follow the evolution of this.
Incidentally, and as reported in my comment #11 in that bug report, I am able to build ports without warnings by using the 2 most sane-looking suggestions found in this question: sudo /usr/bin/xcode-select -switch /Applications/Xcode.app/Contents/Developer and changing developer_dir in /opt/local/etc/macports/macports.conf to /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain
I have macports installed without admin/root privileges, so I was unable to test the xcode-select answers. However, I observed that Pall Melsted's answer worked, but not initially. What I found out was that I had not accepted the Xcode 4.5 license agreement!
If you have just installed Xcode for the purposes of macports, and you haven't accepted the Xcode license yet, you might get the error presented by the original post. When I checked my Xcode version using /usr/bin/xcodebuild -version, I was given the prompt to read and accept the license. After doing so, and after having made the changes suggested by Pall to the macports.conf developer_dir, it all works now.
As alternative: you can make downgrade of Xcode to 4.2.1 version. DMG of Xcode 4.2.1 placed here: https://developer.apple.com/downloads/index.action
After this MacPorts became works fine for me.
This is fixed in MacPorts 2.0.4.
To upgrade:
Download MacPorts 2.0.4 from the install site or run sudo port selfupdate.
Run the MacPorts migration described here to reinstall all ports. This is painful but required to get back to a working state.
You should definitely run sudo xcode-select -switch /Applications/Xcode.app like everyone here says, that'll fix many problems, but certainly not all.
Afaik, all the remaining problems exist within the configuration information for various packages. You might simply reinstall MacPorts as described in the migration instructions, but I found another solution.
You should begin finding all effected port files using commands like grep /Developer/ ..., after executing sudo bash and cd /opt/local naturally.
You should identify all effected ports by using port provides ..., which I piped through sed and sort | uniq. You could simply reinstall all these ports using either port -n upgrade --force ... or separate port uninstall ... and port install ... commands.
I recommend using one large port -n upgrade --force ... command to avoid duplicate rebuilds of dependencies, using the separate uninstall and install commands afterwards.
There are of course various ports for which /Developer exists only inside text config files, meaning you can fix them manually with sed -i -e 's/\/Developer//g' ..., but you cannot do so with binaries obviously.
I'm afraid you must at minimum rebuild all your Python and Perl installations, making this upgrade an ideal time to clean out packages that depend upon older versions, ala python26 and perl5.8.
There are several technically effected ports I decided against rebuilding like fuse4x-kext, who contained /Developer inside Library/Extensions/fuse4x.kext/Contents/MacOS/fuse4x but hasn't prevented sshfs from working correctly.
I had initially installed xcode 3.2.2, after which I installed 4.3. When I ran the xcode-select, I still got the same error about no xcode project in /Applications. I then dug into the /usr/bin/xcodebuild script and found out that this was working correctly, and another instance of xcodebuild (the one installed with xcode 4.3, not the one in /usr/bin) was being run and returning the error:
xcodebuild: error: The directory /Applications does not contain an Xcode project.
It seems the /usr/bin/xcode-select does not work for xcode 4.3, (it's compiled so you can't really see why it's not working). Strings doesn't give any clues. Good thing osx has strace.. oh wait.
Anyways, the best I could do was modify /opt/local/etc/macports.conf
and uncomment the line containing the path to the xcode installation. That seems to fix my problem for the most part.