Hi, guys: I have some problems for creating grib index file. My enviroments are windows 7 32bits and IDL 8.3. 1, In help documents, GRIB_INDEX_WRITE's syntax is : GRIB_INDEX_WRITE, Filename, Gindex but when call it and get the fellowing error: % GRIB_INDEX_WRITE: String expression required in this context: GINDEX. Finally, I think the correct one is: GRIB_INDEX_WRITE, Gindex, Filename 2, I use the fellowing code to create hunderds of grib index files: FOR i=0, n_elements(filenames)-1 DO BEGIN ; create index file gFileName = filenames[i] + '.idx' gindex = GRIB_INDEX_NEW_FROM_FILE(filenames[i], 'shortName,level') GRIB_INDEX_WRITE, gindex, gFileName GRIB_INDEX_RELEASE, gindex ENDFOR but i find the index files are not the same size and become bigger and bigger, and I check the index file contents, and find the grib filenames be preserved. When I read the index files, i get the error: % GRIB_INDEX_READ: Input output problem So how do i solve this problem. Very thanks. Dave