ZIP_FILE_EXTRA_FIELD_SET(3) | Library Functions Manual | ZIP_FILE_EXTRA_FIELD_SET(3)

# NAME

`zip_file_extra_field_set` — set extra field for file in zip

# LIBRARY

libzip (-lzip)

# SYNOPSIS

`#include <zip.h>`

int
`zip_file_extra_field_set`(zip_t *archive, zip_uint64_t index, zip_uint16_t extra_field_id, zip_uint16_t extra_field_index, const zip_uint8_t *extra_field_data, zip_uint16_t len, zip_flags_t flags);

# DESCRIPTION

The `zip_file_extra_field_set`() function sets the extra field with ID (two-byte signature) extra_field_id and index extra_field_index for the file at position index in the zip archive. The extra field's data will be set to extra_field_data and length len. If a new entry shall be appended, set extra_field_index to `ZIP_EXTRA_FIELD_NEW`.

At least one of the following flags must be set:

`ZIP_FL_CENTRAL`
  Set extra field in the archive's central directory.
`ZIP_FL_LOCAL`
  Set extra field in the local file headers.

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 set using `zip_file_extra_field_set`() since they are set by libzip(3) automatically when needed.

# RETURN VALUES

Upon successful completion 0 is returned. Otherwise, -1 is returned and the error code in archive is set to indicate the error.

# ERRORS

`zip_file_extra_field_set`() fails if:

[`ZIP_ER_EF_TOO_LARGE`]
  The extra field size is too large (ID and length need 4 bytes; the maximum length of all extra fields for one file combined is 65536 bytes).
[`ZIP_ER_INVAL`]
  flags does not specify local or central or the extra field is internal to libzip. This error also occurs if extra_field_index is too large.
[`ZIP_ER_MEMORY`]
  Required memory could not be allocated.
[`ZIP_ER_NOENT`]
  index is not a valid file index in archive.

# SEE ALSO

libzip(3), zip_file_extra_field_delete(3), zip_file_extra_field_get(3), zip_file_extra_fields_count(3)

# HISTORY

`zip_file_extra_field_set`() was added in libzip 0.11.

# AUTHORS

Dieter Baron <dillo@nih.at> and Thomas Klausner <wiz@gatalith.at>

April 28, 2026 | NiH