43 lines
1.6 KiB
Markdown
Executable File
43 lines
1.6 KiB
Markdown
Executable File
# Chapter 4 – Advanced File I/O
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## File Metadata and the `stat` Family
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- Use `stat()`, `fstat()`, `lstat()` to retrieve file metadata:
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- File type, size, inode number, permissions, ownership, timestamps (atime, mtime, ctime).
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- The `stat` structure includes all these details.
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## File Types
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- Regular file, directory, symbolic link, character/block device, FIFO, socket.
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- Use macros like `S_ISREG()`, `S_ISDIR()` to test file types.
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## File Permissions and Modes
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- Represented by 12 bits (e.g., `rwxr-xr--`), plus sticky/SUID/SGID bits.
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- Manipulate with `chmod()`, `fchmod()`, `umask()`.
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- Ownership changed with `chown()` and `fchown()`.
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## Links
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- **Hard links**: multiple filenames point to the same inode.
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- **Symbolic links**: separate files that reference other paths; can be broken.
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- Use `link()`, `unlink()`, `symlink()`, `readlink()`.
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## Directories
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- Open with `opendir()`, read entries with `readdir()`.
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- Low-level: `getdents()` system call.
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## File Timestamps
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- `utime()`, `utimes()`, `futimens()`, and `utimensat()` to update access/modification times.
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## File Descriptors and Flags
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- Manipulate with `fcntl()`:
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- Set non-blocking mode (`O_NONBLOCK`), FD_CLOEXEC flag, file locks.
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- Duplicate with `dup()` and `dup2()`.
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## File Locking
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- `flock()` for advisory locking (whole file).
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- `fcntl()` for POSIX record locking (ranges).
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## Temporary Files
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- `tmpfile()`, `mkstemp()` are safe methods to create temp files.
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## Summary
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- Chapter 3 focuses on extended file handling: metadata, links, directories, file modes, and advanced descriptor manipulation.
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