[Haskell-cafe] Re: wanted: haskell one-liners (in the perl sense of one-liners)

Thomas Hartman tphyahoo at gmail.com
Wed Mar 7 07:18:14 EST 2007

In the spirit of making easy things easy, here is a "haskell from
shell" one-line grepper, that uses regexen.

Now, if only I could get pcre-regex installed I would be quite
content. (Still stuck using posix RE for now.)


thartman at linodewhyou:~/learning/haskell/UnixTools$ time ./q-words.sh

real    0m3.186s
user    0m1.900s
sys     0m0.810s

thartman at linodewhyou:~/learning/haskell/UnixTools$ cat q-words.sh
cat /usr/share/dict/american-english | ghc -e 'interact $ unlines.
take 10 . filter ( \x -> x =~ "^q" :: Bool ) . lines' Imports.hs

thartman at linodewhyou:~/learning/haskell/UnixTools$ cat Imports.hs
import Text.Regex.Posix


2007/3/2, Thomas Hartman <tphyahoo at gmail.com>:
> 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.

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