Shell Programming and Scripting

In my ksh file, that refer from pro*c program. From pro*c program i have given a part, those i am unable to understand.i.e.,

if (D_SUCCESS!=system_dev(cmmndstr))
{
efin_trace("Failed to compress report file.\n");
strcpy(errmsg, "Failed to compress report file.");
return D_FAILURE;
}
sprintf(fileatt, "%s/p_rpt.xls.Z", report_dir, report_id);

strcpy(size_script_path,getenv("COM_DIR"));
strcat(size_script_path,"/p_file_size.ksh");
sprintf(cmmndstr,"%s %s",size_script_path,fileatt);



And in ksh file, only this code is present. i.e.,
file_size=`ls -l $1|awk '{print $5}' `
exit $file_size

so please tell me the meaning of this.