{
  "slug": "file-modification-time",
  "term": "File modification time",
  "aliases": [
    "mtime",
    "Modification time",
    "Last modification time"
  ],
  "definition": "File modification time (mtime) is the filesystem timestamp associated with the latest change to a file's contents or a directory's entries.",
  "note": "Writes and truncation update mtime; changing ownership or permissions alone does not. The timestamp can also be set explicitly with utimensat(), subject to permissions, without changing file contents. Filesystem resolution limits the stored value. [linux-inode] [linux-utimensat]\n\nThe default rsync quick check compares file size and mtime, not content. Its default comparison ignores nanoseconds; --modify-window=-1 includes them when the receiver is version 3.1.3 or later. Equal size and mtime are not proof of identical data. [rsync-manual]",
  "related": [
    "inode",
    "inode-change-time",
    "file-access-time",
    "file-birth-time",
    "rsync-quick-check"
  ],
  "citations": [
    {
      "id": "linux-inode",
      "title": "Linux man-pages: inode(7)",
      "url": "https://man7.org/linux/man-pages/man7/inode.7.html",
      "accessed": "2026-10-21"
    },
    {
      "id": "linux-utimensat",
      "title": "Linux man-pages: utimensat(2)",
      "url": "https://man7.org/linux/man-pages/man2/utimensat.2.html",
      "accessed": "2026-10-21"
    },
    {
      "id": "rsync-manual",
      "title": "rsync(1): file selection and modification-time comparison",
      "url": "https://download.samba.org/pub/rsync/rsync.1",
      "accessed": "2026-10-21"
    },
    {
      "id": "hesela-file-times",
      "title": "Hesela: interpreting file timestamps during rsync selection",
      "url": "https://hesela.com/analyses/rsync-delta-shifted-blocks/#file-times",
      "accessed": "2026-10-21"
    }
  ],
  "status": "shipping",
  "advantages": [
    "Provides a low-cost signal for selecting files that may need synchronization."
  ],
  "limitations": [
    "Can be preserved or reset independently of file contents.",
    "Filesystem and comparison precision can hide distinct changes."
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-21"
}