Mircea Draghicescu wrote:
> [...]
> What is the easiest way to run an external command from a Haskell
> program and capture its output (stdout) as a string in Haskell?
Have a look at the function runPiped in
http://www.pms.informatik.uni-muenchen.de/mitarbeiter/panne/haskell_libs/daVinci/DaVinci.hs
which is part of the daVinci for Haskell:
http://www.pms.informatik.uni-muenchen.de/mitarbeiter/panne/haskell_libs/daVinci.html
It connects to an external program and returns (apart from the process
id) two handles for communication: One for reading the stdout from the
other program and another for writing into its stdin. If you only ask
for a simple one-way communication like popen/pclose, simply cut down
runPiped. You can use hGetContents to read from a Handle.
[ AFAIK popen/pclose is not in the POSIX standard, but inclusion in
GHC's libs would be nice anyway. <= Hint! :-) ]
> Also, what are the "handles" mentioned in the ghc Posix library
> and how do they relate to the file descriptors?
Handles are basically Haskell's equivalent of C's FILE*, see
http://haskell.org/onlinelibrary/io.html
Cheers,
Sven
--
Sven Panne Tel.: +49/89/2178-2235
LMU, Institut fuer Informatik FAX : +49/89/2178-2211
LFE Programmier- und Modellierungssprachen Oettingenstr. 67
mailto:[EMAIL PROTECTED] D-80538 Muenchen
http://www.pms.informatik.uni-muenchen.de/mitarbeiter/panne
