# How to read a UTF-8 string **URL:** \ **Category:** HDF5 Library\ **Created:** [September 11, 2019, 3:51pm UTC](https://forum.hdfgroup.org/t/how-to-read-a-utf-8-string/6125 "2019-09-11T15:51:10Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![noman](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/n/d6d6ee/32.png) [@noman](https://forum.hdfgroup.org/u/noman)\ **Post date:** [September 11, 2019, 3:51pm UTC](https://forum.hdfgroup.org/t/how-to-read-a-utf-8-string/6125/1 "2019-09-11T15:51:10Z")
I’m trying to read a string attribute in a HDF5 file that has CSET set to H5T\_CSET\_UTF8. Using h5dump shows the attribute to be: ``` ATTRIBUTE "basePath" { DATATYPE H5T_STRING { STRSIZE H5T_VARIABLE; STRPAD H5T_STR_NULLTERM; CSET H5T_CSET_UTF8; CTYPE H5T_C_S1; } DATASPACE SCALAR DATA { (0): "/screen/%T/" } } ``` I use the following test code to read this: ``` program test use h5lt use hdf5 implicit none integer h5_err integer(hid_t) file_id character(16) string call h5open_f(h5_err) call h5fopen_f('astra.h5', H5F_ACC_RDONLY_F, file_id, h5_err) call H5Eset_auto_f(1, h5_err) ! Reset call h5eclear_f(h5_err) call H5LTget_attribute_string_f(file_id, '.', 'basePath', string, h5_err) print *, h5_err print *, string end program ``` Running the program gives: ``` erpsim1:~/linux_lib/test> ../debug/bin/test 0 ??? ``` In other words I get garbage for the string. I don’t see why the program does not work since the string has only ASCII compatible characters. In any case, what is the correct way to read in this attribute? Obviously there is a way since h5dump can read it. Thanks for any help. ---
**Author:** ![noman](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/n/d6d6ee/32.png) [@noman](https://forum.hdfgroup.org/u/noman)\ **Post date:** [September 11, 2019, 6:36pm UTC](https://forum.hdfgroup.org/t/how-to-read-a-utf-8-string/6125/2 "2019-09-11T18:36:26Z")
From reading other posts it looks like the problem in probably not UTF8 but the fact that the string size is H5T\_VARIABLE. I still, though, need a way to read in an attribute string that can be either of fixed or variable length. Anyone know of any example code for this (using Fortran preferred)? ---
**Author:** ![bljones](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/b/e5b9ba/32.png) [@bljones](https://forum.hdfgroup.org/u/bljones)\ **Post date:** [September 11, 2019, 6:52pm UTC](https://forum.hdfgroup.org/t/how-to-read-a-utf-8-string/6125/3 "2019-09-11T18:52:00Z")
Hi, I have an example that does not use the high level libraries. It reads an attribute that looks like this: $ h5dump vatt.h5 HDF5 “vatt.h5” { GROUP “/” { ATTRIBUTE “MyAttribute” { DATATYPE H5T\_STRING { STRSIZE H5T\_VARIABLE; STRPAD H5T\_STR\_NULLTERM; CSET H5T\_CSET\_ASCII; CTYPE H5T\_C\_S1; } DATASPACE SCALAR DATA { (0): “a variable-length string!” } } } } See the example: [vlenatt\_F03.f90](https://hdf-discourse-1.s3.amazonaws.com/original/2X/3/37b51f911e54a3b94c9c56237516da9d343eb655.f90) (1.5 KB) -Barbara ---
**Author:** ![brtnfld](https://forum.hdfgroup.org/user_avatar/forum.hdfgroup.org/brtnfld/32/1444_2.png) [@brtnfld](https://forum.hdfgroup.org/u/brtnfld)\ **Post date:** [September 11, 2019, 7:34pm UTC](https://forum.hdfgroup.org/t/how-to-read-a-utf-8-string/6125/4 "2019-09-11T19:34:04Z")
The HL API you are using can’t read VL strings. I would take a look at the examples found here: [https://support.hdfgroup.org/HDF5/examples/api-fortran.html](https://support.hdfgroup.org/HDF5/examples/api-fortran.html) and in particular, h5ex\_t\_string\_F03.f90 h5ex\_t\_vlen\_F03.f90 h5ex\_t\_vlenatt\_F03.f90 h5ex\_t\_vlstring.f90 h5ex\_t\_vlstring\_F03.f90 Use the Fortran 2003 H5Aread\_f version for reading both datatypes. You can get the datatype of the attribute beforehand, and then pass the correct arguments to H5Aread accordingly. Scot ---
**Author:** ![gerard.henry](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/g/4bbf92/32.png) [@gerard.henry](https://forum.hdfgroup.org/u/gerard.henry)\ **Post date:** [December 15, 2020, 2:03pm UTC](https://forum.hdfgroup.org/t/how-to-read-a-utf-8-string/6125/5 "2020-12-15T14:03:00Z")
Hello, sorry to get back on this ancient thread, but actually i have this problem and unable to solve it. With your program, and the same h5 file, except that H5T\_CSET\_ASCII is replaced by H5T\_CSET\_UTF8, it fails with: ``` $ ./vlenatt_F03 HDF5-DIAG: Error detected in HDF5 (1.12.0) thread 0: #000: H5A.c line 726 in H5Aread(): unable to read attribute major: Attribute minor: Read failed #001: H5VLcallback.c line 1232 in H5VL_attr_read(): attribute read failed major: Virtual Object Layer minor: Read failed #002: H5VLcallback.c line 1199 in H5VL__attr_read(): attribute read failed major: Virtual Object Layer minor: Read failed #003: H5VLnative_attr.c line 176 in H5VL__native_attr_read(): unable to read attribute major: Attribute minor: Read failed #004: H5Aint.c line 635 in H5A__read(): unable to convert between src and dst datatypes major: Attribute minor: Feature is unsupported #005: H5T.c line 4815 in H5T_path_find(): can't find datatype conversion path major: Datatype minor: Can't get value #006: H5T.c line 5028 in H5T__path_find_real(): no appropriate function for conversion path major: Datatype minor: Unable to initialize object Program received signal SIGSEGV: Segmentation fault - invalid memory reference. ``` How it is possible to read utf-8 string? in the example file h5ex\_t\_vlenatt\_F03.f90, there is no UTF-8. What’s the correct way? Thanks in advance, Gérard ---
**Author:** ![brtnfld](https://forum.hdfgroup.org/user_avatar/forum.hdfgroup.org/brtnfld/32/1444_2.png) [@brtnfld](https://forum.hdfgroup.org/u/brtnfld)\ **Post date:** [July 23, 2021, 2:59pm UTC](https://forum.hdfgroup.org/t/how-to-read-a-utf-8-string/6125/6 "2021-07-23T14:59:52Z")
For future reference, here is an example with UTF-8 string and Fortran. [h5ex\_t\_vlstring\_F03.f90](https://hdf-discourse-1.s3.amazonaws.com/original/2X/7/7fdbc11cdcbe6eb943950f625ea2d14a65677455.f90) (3.8 KB)