Deletes an attribute from an object.
Examples
file <- tempfile(fileext = ".h5")
h5_write(file, "data", 1)
h5_write_attr(file, "data", "attr1", I("some info"))
print(h5_ls_attr(file, "data")) # "attr1"
#> [1] "attr1"
h5_delete_attr(file, "data", "attr1")
print(h5_ls_attr(file, "data")) # character(0)
#> character(0)
unlink(file)
