问题
I'm a newbie to haskell and cabal, so I'm probably missing something simple.
I updated cabal-install:
sudo cabal install cabal-install
Password:
Resolving dependencies...
Configuring cabal-install-1.22.0.0...
Building cabal-install-1.22.0.0...
Installed cabal-install-1.22.0.0
Updating documentation index
However cabal --version says:
cabal-install version 1.18.0.5
using version 1.18.1.4 of the Cabal library
What happened to cabal-install 1.22.0.0?
回答1:
There are two ways of making cabal install packages globally. Note that, as a result, cabal may require sudo.
This command will install <PACKAGE> globally:
$ cabal install <PACKAGE> --global
As a more general solution, edit the file ~/.cabal/config and set user-install to False. This will automatically set the --global flag so you can just write cabal install <PACKAGE> without any worry. Here's a snippet of my config file:
...
-- split-objs: False
-- executable-stripping: True
user-install: False
-- package-db:
-- flags:
...
You may also want to set root-cmd to sudo if it's not already, so that cabal will automatically prompt for the root password when it encounters a permission problem.
There's some more info online here.
回答2:
I see that there's an updated cabal at ~/Library/Haskell/bin, so I could replace /usr/bin/cabal with a symbolic link to this copy or I could copy this binary to /usr/bin.
I'm still interested if there is a more elegant/canonical way to make sure the new cabal is what gets used by default.
回答3:
TLDR: Try running hash -r
Bash has a PATH hashtable that maps commands to the location of binaries. You may still have an old version of cabal installed somewhere in your PATH (possibly in a sandbox). Since cabal is not a new command, the hashtable will keep serving up the old version. hash -r rebuilds the hashtable, so the shell will correctly find the new version (providing it appears earlier in your path than the old one).
来源：https://stackoverflow.com/questions/27826656/cabal-install-cabal-install-doesnt-update-cabal-version-in-osx