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# File formats and file metadata

## exiftool

see examples at https://exiftool.org/examples.html

### List of all metadata fields

Metadata is usually stored in one of the following:

  - XMP https://www.exiftool.org/TagNames/XMP.html (especially XMP *dc* Tags)
  - EXIF https://exiftool.org/TagNames/EXIF.html
  - IPTC https://exiftool.org/TagNames/IPTC.html Older format, replaced more and more by XMP.

### list all metadata

```
exiftool /images/1988-klassenfoto-elzmatte-3.jpg
```

in RDF format:

```
exiftool -a -g -struct -X 1988-klassenfoto-elzmatte-3.jpg
```

### get certain field

Where -Subject stands for the Subject field in XMP.

```
exiftool -s -Subject /images/1988-klassenfoto-elzmatte-3.jpg
```

### overwrite field

#### delete/remove

```
exiftool -Subject="" -overwrite_original 1988-klassenfoto-elzmatte-3.jpg
```

#### remove single term

```
exiftool -Subject-="1988" -overwrite_original /image/1988-klassenfoto-elzmatte-3.tif
```

#### add single term

```
exiftool -Subject="1988" -overwrite_original /image/1988-klassenfoto-elzmatte-3.tif
```

to add more terms, keeping the existing ones:

```
exiftool -Subject+="1988" -Subject+="roger" -overwrite_original /image/1988-klassenfoto-elzmatte-3.tif
```

#### add multiple terms

This will overwrite existing terms.

```
exiftool -sep ", " -Subject="1988, roger" -overwrite_original /image/1988-klassenfoto-elzmatte-3.tif
```

## droid

Format Identifier CLI and GUI based on PRONOM PUID

https://www.nationalarchives.gov.uk/information-management/manage-information/preserving-digital-records/droid/

## fido

Format Identifier CLI based on PRONOM PUID

https://github.com/openpreserve/fido

## jhove

CLI and GUI tool for format identification and validation. Can be used e.g. to determine if a XML or SVG is valid.

https://jhove.openpreservation.org/

## siegfried

CLI command tool. Shows PRONOM PUID, mimetype.

https://openpreservation.org/blogs/siegfried-pronom-based-file-format-identification-tool/

## Sigcheck

Sigcheck is a command-line utility that shows file version number, timestamp information, and digital signature details, including certificate chains.

See https://learn.microsoft.com/en-us/sysinternals/downloads/sigcheck

## veraPDF

PDF/A validator and repairer. GUI and CLI.

https://verapdf.org/home/