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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

# create an SOZip-enabled file and validate
# Requires GDAL >= 3.7
f <- system.file("extdata/ynp_fires_1984_2022.gpkg", package="gdalraster")

if (as.integer(gdal_version()[2]) >= 3070000) {
  zip_file <- tempfile(fileext=".zip")
  addFilesInZip(zip_file, f, full_paths=FALSE, sozip_enabled="YES")
  zip_vsi <- file.path("/vsizip", zip_file)
  print("Files in zip archive:")
  print(vsi_read_dir(zip_vsi))
  print("SOZip metadata:")
  print(vsi_get_file_metadata(zip_vsi, domain="ZIP"))

  vsi_unlink(zip_file)
}
#> adding /home/runner/work/_temp/Library/gdalraster/extdata/ynp_fires_1984_2022.gpkg ...
#> 0...10...20...30...40...50...60...70...80...90...100 - done.
#> [1] "Files in zip archive:"
#> [1] "ynp_fires_1984_2022.gpkg"
#> [1] "SOZip metadata:"
#> $START_DATA_OFFSET
#> [1] "54"
#> 
#> $COMPRESSION_METHOD
#> [1] "8 (DEFLATE)"
#> 
#> $COMPRESSED_SIZE
#> [1] "164729"
#> 
#> $UNCOMPRESSED_SIZE
#> [1] "307200"
#> 
#> $SOZIP_FOUND
#> [1] "YES"
#> 
#> $SOZIP_VERSION
#> [1] "1"
#> 
#> $SOZIP_OFFSET_SIZE
#> [1] "8"
#> 
#> $SOZIP_CHUNK_SIZE
#> [1] "32768"
#> 
#> $SOZIP_START_DATA_OFFSET
#> [1] "164848"
#> 
#> $SOZIP_VALID
#> [1] "YES"
#> 
#> [1] 0