TRUNCATE(3POSIX)

📦 version 2017a, in debian bookworm, debian trixie, ubuntu jammy, ubuntu noble, ubuntu resolute, ubuntu stonking

🌸 TRUNCATE(3POSIX) — bestie, it's the POSIX Programmer's Manual edition 🎀

okay so quick vibe check before we even start: this page lives in the POSIX Programmer's Manual. The Linux implementation of this interface may differ (so pls consult the corresponding Linux manual page for the deets on Linux behavior), or honestly the interface may not even be implemented on Linux at all. 🙈

✨ NAME ✨

truncate — truncate a file to a specified length 💅

🦋 SYNOPSIS 🦋

#include <unistd.h>

int truncate(const char *path, off_t length);

💖 DESCRIPTION 💖

So truncate() shall cause the regular file named by path to have a size which shall be equal to length bytes. That's it, that's the whole job, and it ate. 🔥

If the file was previously larger than length, the extra data is discarded. Bye bye data, no cap.

If the file was previously shorter than length, its size is increased, and the extended area appears as if it were zero-filled. ✨

The application shall ensure that the process has write permission for the file. Not optional, bestie.

If the request would cause the file size to exceed the soft file size limit for the process, the request shall fail and the implementation shall generate the SIGXFSZ signal for the process. 😭 that's a real signal, not a drill.

The truncate() function shall not modify the file offset for any open file descriptions associated with the file. Upon successful completion, truncate() shall mark for update the last data modification and last file status change timestamps of the file, and the S_ISUID and S_ISGID bits of the file mode may be cleared. 👑

⭐ RETURN VALUE ⭐

Upon successful completion, truncate() shall return 0. Otherwise, -1 shall be returned, and errno set to indicate the error. classic.

🔥 ERRORS 🔥

The truncate() function shall fail if:

  • EINTR — A signal was caught during execution. 😤 rude but okay
  • EINVAL — The length argument was less than 0.
  • EFBIG or EINVAL — The length argument was greater than the maximum file size. too big, babe
  • EIO — An I/O error occurred while reading from or writing to a file system.
  • EACCES — A component of the path prefix denies search permission, or write permission is denied on the file.
  • EISDIR — The named file is a directory. bestie that's a whole folder 💀
  • ELOOP — A loop exists in symbolic links encountered during resolution of the path argument.
  • ENAMETOOLONG — The length of a component of a pathname is longer than {NAME_MAX}.
  • ENOENT — A component of path does not name an existing file or path is an empty string.
  • ENOTDIR — A component of the path prefix names an existing file that is neither a directory nor a symbolic link to a directory, or the path argument contains at least one non-<slash> character and ends with one or more trailing <slash> characters and the last pathname component names an existing file that is neither a directory nor a symbolic link to a directory.
  • EROFS — The named file resides on a read-only file system. 🧊 frozen fr

The truncate() function may fail if:

  • ELOOP — More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the path argument.
  • ENAMETOOLONG — The length of a pathname exceeds {PATH_MAX}, or pathname resolution of a symbolic link produced an intermediate result with a length that exceeds {PATH_MAX}.
heads up: the following sections are informative. they're the chill extra credit section, not the rules. 🫶

🌈 EXAMPLES 🌈

None.

🍓 APPLICATION USAGE 🍓

None.

🧚 RATIONALE 🧚

None.

💜 FUTURE DIRECTIONS 💜

None.

👑 SEE ALSO 👑

  • open()
  • The Base Definitions volume of POSIX.1‐2017, <unistd.h>

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

that's the whole thing, you understood it perfectly, I'm so proud 🥹 this page is brought to you by IEEE/The Open Group, dated 2017, and it's filed under TRUNCATE(3POSIX) — go forth and truncate responsibly, mwah 💖✨

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