Re: librec examples

[wim]

Hi ,

after some digging I put this basic example together, maybe it can help 
others in the future:

Just an example of selecting some records and fields through the 
C-library from a recutils database , i used

this chem.rec file

https://gist.githubusercontent.com/Gavinok/c3510aea2386e755bcc17d4d36fa5dec/raw/15ff07952004ff3bdb51d7ef60270ed74521fff1/chem.rec

It's as bare bones of an example I could make, no error checking or 
nothing. Just the bare minimum to get started.

Check out the utils/recsel.c if you want to the whole package.

Example:

#include <rec.h>
#include <stdio.h>

// constants used for the query
char      *recutl_sex_str      = "Symbol = \"Mg\"";
rec_sex_t  recutl_sex          = NULL;
char      *recutl_quick_str    = NULL;
char      *recsel_fex_str      = NULL;
rec_fex_t  recsel_fex          = NULL;
char      *recutl_type         = NULL;
bool       recsel_collapse     = false;
bool       recsel_count        = false;
bool       recutl_insensitive  = false;
bool       recsel_descriptors  = false;
rec_fex_t  recutl_sort_by_fields  = NULL;
rec_fex_t  recsel_group_by_fields = NULL;
rec_writer_mode_t recsel_write_mode = REC_WRITER_NORMAL;
char      *recsel_password     = NULL;
bool       recsel_uniq         = false;
size_t     recutl_random       = 0;
char      *recsel_join         = NULL;

int main (int argc, char *argv[])
{
    // firste open our rec database file
    FILE *fp;
    fp = fopen("chem.rec","r");
    // Create our database in memory
    rec_db_t db;
    db = rec_db_new();
    // Declare our recordset variable
    rec_rset_t rset;
    // Declare the file parser and load the recordset into memory.
    rec_parser_t parser;
    parser = rec_parser_new(fp,"chem.rec");
      while (rec_parse_rset (parser, &rset))
    {
        rec_db_insert_rset(db,rset,rec_db_size(db));
    }

    //Create the Search Expression
    char search[] = "Symbol~\"M\"";
    rec_sex_t sex = rec_sex_new(recutl_insensitive);
    //Compile the Search Expression (sex)
    rec_sex_compile(sex,search);

    //What fields will we show:
    //Create a field expression
//    rec_fex_t fex = rec_fex_new("Name",REC_FEX_CSV);
    rec_fex_t fex = NULL;

    //Queries our in memory database
    rset = 
rec_db_query(db,recutl_type,recsel_join,0,sex,recutl_quick_str,recutl_random,fex,recsel_password,recsel_group_by_fields,recutl_sort_by_fields,0);
    //Create an iterator to walk through the recordsets
    rec_mset_iterator_t iter = rec_mset_iterator(rec_rset_mset(rset));
    void *data;
    rec_mset_elem_t elem;
    //loop over the recordset and print to stdout
    while (rec_mset_iterator_next (&iter, MSET_ANY, (const void **) 
&data, &elem))
    {
        rec_mset_iterator_t iter;
        char *dat;
        size_t num_field, num_elem, num_fields, num_elems;
        rec_record_t record =  (rec_record_t) data;
        num_elems =  rec_record_num_elems(record);
        iter = rec_mset_iterator(rec_record_mset(record));
        while (rec_mset_iterator_next (&iter, MSET_ANY, (const void **) 
&data, &elem))
        {
            rec_field_t field = (rec_field_t) data;
            const char *fvalue;
            const char *fname;
            fvalue = rec_field_value(field);
            fname = rec_field_name(field);
            printf("\n %s = %s",fname,fvalue);
        }
    }
}



Have fun,

Kind Regards,

Wim Stockman



Op 04-04-2023 om 07:22 schreef Jose E. Marchesi:
> > Hi would it be possible to give a basic sample of the librec c library
> >
> > how to insert a record ?
> >
> > how to select a record ?
> >
> > Let's say for a basic adresse book example
> The recutils themselves (recsel, recins, etc) are just simple little C
> programs that use librec.
>
> You can find them under src/ in the recutils source distribution.