zip_file_replace

zip_file_add, zip_file_replace —
add file to zip archive or replace file in zip archive

libzip (-lzip)

#include <zip.h>

zip_int64_t
zip_file_add(zip_t *archive, const char *name, zip_source_t *source, zip_flags_t flags);

int
zip_file_replace(zip_t *archive, zip_uint64_t index, zip_source_t *source, zip_flags_t flags);

The function zip_file_add() adds a file to a zip archive, while zip_file_replace() replaces an existing file in a zip archive. The argument archive specifies the zip archive to which the file should be added. name is the file's name in the zip archive (for zip_file_add()), while index specifies which file should be replaced (for zip_file_replace()). The flags argument can be any combination of ZIP_FL_OVERWRITE with one of ZIP_FL_ENC_*:
Overwrite any existing file of the same name. For zip_file_add only.
Guess encoding of name (default). (Only CP-437 and UTF-8 are recognized.)
Interpret name as UTF-8.
Interpret name as code page 437 (CP-437).
The data is obtained from the source argument, see zip_source(3).

NOTE: zip_source_free(3) should not be called on a source after it was used successfully in a zip_file_add or zip_file_replace call.

Please also note that when using zip_replace, the target file's extra field information will be deleted since this usually is dependent on the file contents. If you want to keep them, query them beforehand with zip_file_extra_field_get(3) and restore them after zip_replace with zip_file_extra_field_set(3).

Upon successful completion, zip_file_add() returns the index of the new file in the archive, and zip_file_replace() returns 0. Otherwise, -1 is returned and the error code in archive is set to indicate the error. 

zip_source_t *s;
const char buf[]="teststring";

if ((s=zip_source_buffer(archive, buf, sizeof(buf), 0)) == NULL ||
    zip_file_add(archive, name, s, ZIP_FL_ENC_UTF_8) < 0) {
    zip_source_free(s);
    printf("error adding file: %s\n", zip_strerror(archive));
}

zip_file_add() and zip_file_replace() fail if:
[]
There is already a file called name in the archive. (Only applies to zip_file_add(), and only if ZIP_FL_OVERWRITE is not provided).
[]
source or name are NULL, or index is invalid.
[]
Required memory could not be allocated.
[]
Archive was opened in read-only mode.

libzip(3), zip_source(3)

zip_file_add() and zip_file_replace() were added in libzip 0.11.

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