ZIP_FILE_SET_MTIME(3)

💖 ZIP_FILE_SET_MTIME 💖

okay bestie, we're in ZIP_FILE_SET_MTIME(3), aka the Library Functions Manual, and today's hyperfixation is setting the last modification time (mtime) for a file in a zip. yes. we're doing timestamps. it's giving archival girlboss energy and I am obsessed. 🎀

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✨ NAME ✨

zip_file_set_dostime, zip_file_set_mtime — set last modification time (mtime) for file in zip

📚 LIBRARY 📚

libzip (-lzip) — no cap, that's the one you're linking against.

🫶 SYNOPSIS 🫶

#include <zip.h>

int
zip_file_set_dostime(zip_t *archive, zip_uint64_t index,
    zip_uint16_t dostime, zip_uint16_t dosdate, zip_flags_t flags);

int
zip_file_set_mtime(zip_t *archive, zip_uint64_t index, time_t mtime,
    zip_flags_t flags);

🌸 DESCRIPTION 🌸

so zip_file_set_mtime() sets the last modification time (mtime) for the file sitting at position index in the zip archive, and it sets it to mtime. that's the whole vibe. 💅

Currently, no support for any flags is implemented. — literally none, bestie, the flag situation is a void.

here's the tea though: inside the zip archive, the time and date are stored as two 16-bit integers. so if you wanna set those values directly, you call zip_file_set_dostime() instead. here's how the bits are divvied up 🧚

the values of the time bytes are defined as follows:

• 0-4 — seconds divided by two (1-2 = 1, 3-4 = 2, ...)
• 5-10 — minute (0-59)
• 11-15 — hour (0-23)

the values of the date bytes are defined as follows:

• 0-4 — day of the month (1-31)
• 5-8 — month (January = 1, February = 2, ...)
• 9-15 — year offset from 1980 (1980 = 0, 1981 = 1, ...)

look at those little bit ranges. so compact. so iconic. 🔥

🦋 RETURN VALUES 🦋

if it works? you get 0 back. slay. 💖

if it doesn't? you get -1, and the error information in archive gets set to tell you what went wrong. sad girl hours but at least you get diagnostics.

💀 ERRORS 💀

zip_file_set_dostime() and zip_file_set_mtime() fail if:

• [ZIP_ER_INVAL] — index is not a valid file index in archive. bestie that file does not exist, stop trying to timestamp a ghost 🙈
• [ZIP_ER_MEMORY] — required memory could not be allocated. the machine said no 😭
• [ZIP_ER_OPNOTSUPP] — traditional PKWare encryption uses the file's mtime, therefore it cannot be changed without re-encrypting the data. yeah so this one's locked, the encryption literally eats the mtime. you can't just edit it, you'd have to re-encrypt the whole thing.
• [ZIP_ER_RDONLY] — the archive was opened in read-only mode. read-only means read-only, we don't write here ✋

👑 SEE ALSO 👑

libzip(3), zip_stat(3)

🌈 HISTORY 🌈

• zip_file_set_mtime() was added in libzip 1.0.
• zip_file_set_dostime() was added in libzip 1.6.

glow-ups across releases, we love to see it ⭐

🎀 AUTHORS 🎀

Dieter Baron <dillo@nih.at> and Thomas Klausner <wiz@gatalith.at> — the actual main characters who wrote this 💜

⚠️ CAVEATS ⚠️

following historical practice, the zip_file_set_mtime() function translates the time from the zip archive into the local time zone. if you want to avoid this, use the zip_file_set_dostime() function instead. fr fr, timezone surprises are not the vibe check you want.

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and that's the whole page, bestie 🫶 this was written up on June 18, 2022 and shipped out by the Debian girlies under ZIP_FILE_SET_MTIME(3). go set some timestamps, you absolute legend 💅✨