zip_file_extra_field_get, zip_file_extra_field_get_by_id
get extra field for file in zip

libzip (-lzip)

#include <zip.h>

const zip_uint8_t *
zip_file_extra_field_get(zip_t *archive, zip_uint64_t index, zip_uint16_t extra_field_index, zip_uint16_t *idp, zip_uint16_t *lenp, zip_flags_t flags);

const zip_uint8_t *
zip_file_extra_field_get_by_id(zip_t *archive, zip_uint64_t index, zip_uint16_t extra_field_id, zip_uint16_t extra_field_index, zip_uint16_t *lenp, zip_flags_t flags);

The zip_file_extra_field_get() function returns the extra field with index extra_field_index for the file at position index in the zip archive. This pointer should not be modified or free(3)'d, and becomes invalid when archive is closed. If idp is not NULL, the integer to which it points will be set to the ID (two-byte signature) of the selected extra field. If lenp is not NULL, the integer to which it points will be set to the length of the extra field. Generally speaking, lenp and idp should be passed since only the extra field data is returned (i.e., neither the ID nor the length, if the idp and lenp arguments are not provided).

The following flags are supported:

Return extra fields from the archive's central directory.
Return extra fields from the local file headers.
Return the original unchanged extra fields, ignoring any changes made.

The zip_file_extra_field_get_by_id() function returns the extra field with ID (two-byte signature) extra_field_id and index extra_field_index (in other words, the extra_field_index'th extra field with ID extra_field_id) The other arguments are the same as for zip_file_extra_field_get().

Upon successful completion, a pointer to an extra field is returned, or NULL if there is no extra field with that extra_field_index for the file with index index. In case of an error, NULL is returned and the error code in archive is set to indicate the error.

zip_file_extra_field_get() and zip_file_extra_field_get_by_id() fail if:
index is not a valid file index in archive, or extra_field_index is not a valid extra file index (for ID extra_field_id).

libzip(3), zip_file_extra_field_delete(3), zip_file_extra_field_set(3), zip_file_extra_fields_count(3)

zip_file_extra_field_get() and zip_file_extra_field_get_by_id() were added in libzip 0.11.

Dieter Baron <> and Thomas Klausner <>

Please note that the extra field IDs 0x0001 (ZIP64 extension), 0x6375 (Infozip UTF-8 comment), and 0x7075 (Infozip UTF-8 file name) can not be read using zip_file_extra_field_get() since they are used by libzip(3) internally.