Running a program (gperf) inside another C program

Running a program (gperf) inside another C program

Post by Alexander » Tue, 27 May 2008 22:41:36

Hello, apart from using fork() and exec*(), or system(), is there any
other way to run the gperf command line program inside a C program? I
need to generate at run-time a perfect hash function, and it seems
that gperf has no API to execute it programmatically, so the only way
is to call it as an external program, and instruct it to write the
ouput code to a certain file whose path I know.
Thanks a lot

Running a program (gperf) inside another C program

Post by Flash Gord » Tue, 27 May 2008 23:13:46

Alexander Mahone wrote, On 26/05/08 14:41:

In standard C the only method is system(), anything else is system
specific, so I suggest asking in comp.unix.programmer.

A better method almost certainly is to either find or write a library
that does what you want. If you search the group you will find that
hashing has been discussed several times here. Alternatively a simple
google search for "perfect has library" without the quotes shows some
Flash Gordon


Running a program (gperf) inside another C program

Post by roberso » Tue, 27 May 2008 23:46:09

In article < XXXX@XXXXX.COM >,

Note that C does not define fork() or exec*(), only system().

Which system() should do fine for.

Anything beyond system() is system-specific.

Based upon your reference to fork() and exec*(), it looks like you
might be using a POSIX type system. If so, then -possibly-,
depending on your system architecture and how exactly gperf was
compiled, you -might- be able to use operating system facilities to
request that gperf be loaded -as if- it were a dynamic library,
find it's entry point, and dispatch to that. Common facility
names that might give this kind of access are dlopen() and dlsym().
You might or might not be able to find a symbol within the program
that gives you a callable API; if not, then you would still have
to create command line arguments, possibly use dup2() or similiar
OS facilities do feed the program with internal streams instead of
creating a real file...

On the other hand, the kinds of systems that tend to make hacks
like the above possible, usually have ways of "pre-linking"
programs: in such cases, the speed difference between the hack I
mentioned vs invocation via system() is probably close to unmeasurable.

"It's a hard life sometimes and the biggest temptation is to let
how hard it is be an excuse to weaken." -- Walter Dean Myers

Running a program (gperf) inside another C program

Post by Keith Thom » Wed, 28 May 2008 03:33:49

Flash Gordon < XXXX@XXXXX.COM > writes:

You mean "perfect hash library", yes?

Keith Thompson (The_Other_Keith) XXXX@XXXXX.COM < ~kst>
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

Running a program (gperf) inside another C program

Post by Flash Gord » Wed, 28 May 2008 06:31:50

Keith Thompson wrote, On 26/05/08 19:33:

Yes, thank you.
Flash Gordon