Skip to contents

Get metadata on files

Source: R/RcppExports.R
vsi_get_file_metadata.Rd

vsi_get_file_metadata() returns metadata for file system objects. Implemented for network-like filesystems. Starting with GDAL 3.7, implemented for /vsizip/ with SOZip metadata. Wrapper of VSIGetFileMetadata() in the GDAL Common Portability Library.

Usage

vsi_get_file_metadata(filename, domain)

Arguments

filename

Character string. The path of the file system object to be queried.

domain

Character string. Metadata domain to query. Depends on the file system, see Details.

Value

A named list of values, or NULL in case of error or empty list.

Details

The metadata available depends on the file system. The following are supported as of GDAL 3.9:

  • HEADERS: to get HTTP headers for network-like filesystems (/vsicurl/, /vsis3/, /vsgis/, etc).

  • TAGS: for /vsis3/, to get S3 Object tagging information. For /vsiaz/, to get blob tags.

  • STATUS: specific to /vsiadls/: returns all system-defined properties for a path (seems in practice to be a subset of HEADERS).

  • ACL: specific to /vsiadls/ and /vsigs/: returns the access control list for a path. For /vsigs/, a single XML=xml_content string is returned.

  • METADATA: specific to /vsiaz/: blob metadata (this will be a subset of what domain=HEADERS returns).

  • ZIP: specific to /vsizip/: to obtain ZIP specific metadata, in particular if a file is SOZIP-enabled (SOZIP_VALID=YES).

See also

vsi_stat(), addFilesInZip()

Examples

# validate an SOZip-enabled file
# Requires GDAL >= 3.7
f <- system.file("extdata/ynp_features.zip", package = "gdalraster")

zf <- file.path("/vsizip", f)
# files in zip archive
vsi_read_dir(zf)
#> [1] "readme_lf_forest_canopy_cover.txt" "readme_lf_operational_roads.txt"  
#> [3] "readme_ynp_vector_features.txt"    "ynp_bnd_metadata.html"            
#> [5] "ynp_features.gpkg"                

# SOZip metadata for ynp_features.gpkg
zf_gpkg <- file.path(zf, "ynp_features.gpkg")
vsi_get_file_metadata(zf_gpkg, domain = "ZIP")
#> $START_DATA_OFFSET
#> [1] "5188"
#> 
#> $COMPRESSION_METHOD
#> [1] "8 (DEFLATE)"
#> 
#> $COMPRESSED_SIZE
#> [1] "541249"
#> 
#> $UNCOMPRESSED_SIZE
#> [1] "1241088"
#> 
#> $SOZIP_FOUND
#> [1] "YES"
#> 
#> $SOZIP_VERSION
#> [1] "1"
#> 
#> $SOZIP_OFFSET_SIZE
#> [1] "8"
#> 
#> $SOZIP_CHUNK_SIZE
#> [1] "32768"
#> 
#> $SOZIP_START_DATA_OFFSET
#> [1] "546495"
#> 
#> $SOZIP_VALID
#> [1] "YES"
#>