Difference: LHCComputingGrid (8 vs. 9)

• Read/write C++ streams to storage elements of the LCG:

http://pstreams.sourceforge.net

#include "gstream.h"

int main(int argc, char *argv[])
{
    // Open the datafile for reading.
    igstream ifile("/grid/cms/alaszlo/some_datafile.dat");
        // Extract data from your datafile with 'igstream::operator>>' or with 'igstream::read(char*, int)'.
    // Close the datafile.
    ifile.close();

    // Open the datafile for writing.
    ogstream ofile("/grid/cms/alaszlo/some_datafile.dat");
        // Write data to your datafile with 'ogstream::operator<<' or with 'ogstream::write(char*, int)'.
    // Close the datafile.
    ofile.close();

    // Open the datafile for reading, through a filter program.
    igpstream ipfile("/grid/cms/alaszlo/some_datafile.gz", "gunzip --stdout %f");
        // Extract data from your datafile with 'igpstream::operator>>' or with 'igpstream::read(char*, int)'.
    // Close the datafile.
    ipfile.close();

    // Open the datafile for writing.
    ogpstream opfile("/grid/cms/alaszlo/some_datafile.dat.gz", "gzip - > %f");
        // Write data to your datafile with 'ogpstream::operator<<' or with 'ogpstream::write(char*, int)'.
    // Close the datafile.
    opfile.close();

    return 0;
}

You can get the library files here: pstream.h, gstream.h, gstream.cc. Before you can use it you have to export the following environmental variables:

export VO = your_vo (for bash), or setenv VO your_vo (for tcsh), and

export DEST = your_favourite_storage_element (for bash), or setenv DEST your_favourite_storage_element (for tcsh).

Setting the environmental variable TMPDIR is optional. This specifies the local (or AFS) directory, where the datafiles are staged out (therefore, it has to have large disk space!). E.g.:

export TMPDIR = /tmp (for bash), or setenv TMPDIR /tmp (for tcsh).

If not specified, the current working directory ($PWD) is used, as this is recommended for grid jobs (the working nodes have large disk spaces).

-- AndrasLaszlo - 17 Mar 2006