To answer my original question, here's a few ways to accomplish what I
wanted with haskell
Perl is still a lot faster than ghc -e, but I guess if you wanted
speed you could compile first.
********************************************************************
thartman@linodewhyou:~/learning/haskell/UnixTools$ ls -l
total 16
-rw-r--r-- 1 thartman thartman 2726 Dec 20 07:56 UnixTools.hs
-rw-r--r-- 1 thartman thartman 82 Jan 7 07:18 echo.hs
-rwxr--r-- 1 thartman thartman 790 Mar 4 05:02 oneliners.sh
-rwxr--r-- 1 thartman thartman 646 Mar 4 04:18 oneliners.sh~
thartman@linodewhyou:~/learning/haskell/UnixTools$ ./oneliners.sh
haskell, ghc -e pipe
16
real 0m1.652s
user 0m0.600s
sys 0m0.030s
**********
haskell, hmap pipe
16
real 0m1.549s
user 0m0.410s
sys 0m0.200s
**********
haskell, two pipes
16
real 0m2.153s
user 0m0.900s
sys 0m0.370s
**********
perl, two pipes
16
real 0m0.185s
user 0m0.010s
sys 0m0.100s
thartman@linodewhyou:~/learning/haskell/UnixTools$
thartman@linodewhyou:~/learning/haskell/UnixTools$ cat oneliners.sh
hmap (){ ghc -e "interact ($*)"; }
hmapl (){ hmap "unlines.($*).lines" ; }
hmapw (){ hmapl "map (unwords.($*).words)" ; }
function filesizes () {
find -maxdepth 1 -type f | xargs du
}
echo haskell, ghc -e pipe
time filesizes | ghc -e 'interact $ (++"\n") . show . sum . map ( (
read :: String -> Integer ) . head . words ) . lines '
echo "**********"
echo haskell, hmap pipe
time filesizes | hmap '(++"\n") . show . sum . map ( ( read :: String
-> Integer ) . head . words ) . lines'
echo "**********"
echo haskell, two pipes
time filesizes | hmapl "map ( head . words )" | hmap '(++"\n") . show
. sum . map ( read :: String -> Integer ) . lines'
echo "**********"
echo perl, two pipes
time filesizes | perl -ane 'print "$F[0]\n"' | perl -e '$sum += $_
while <>; print "$sum\n"'
2007/3/2, Thomas Hartman
Okay, I am aware of
http://haskell.org/haskellwiki/Simple_unix_tools
which gives some implementation of simple unix utilities in haskell.
But I couldn't figure out how to use them directly from the shell, and of course that's what most readers will probably wnat.
Or let me put it another way.
Is there a way to do
find -maxdepth 1 -type f | xargs du | perl -ane 'print "\$F[0]\n"' | perl -e '$sum += $_ while <>; print "$sum\n"'
as a shell command that idiomatically uses haskell?
For non-perlers, that sums up the disk usage of all files in the current directory, skipping subdirs.
print "\$F[0]\n
looks at the first (space delimited) collumn of output.
perl -e '$sum += $_ while <>; print "$sum\n"'
, which is I guess the meat of the program, sums up all the numbers spewed out of the first column, so in the end you get a total.
So, anyone out there want to establish a haskell one liner tradition?
:)
thomas.