File I/O on Nalar

Understand Linux File Descriptor Duplication and Shell Redirection

Fri, 04 Sep 2026 00:00:00 +0700

Shell redirection looks compact:

copied = false, 1600)" class="absolute right-3 top-3 z-10 rounded-lg border border-line-strong bg-surface px-2 py-1 font-mono text-[0.65rem] text-muted opacity-0 transition group-hover:opacity-100 hover:bg-ink hover:text-white dark:border-night-line dark:bg-night dark:text-night-muted dark:hover:bg-white dark:hover:text-ink">

command >output.log 2>&1

But that syntax hides a useful systems concept. The shell is not asking the command to “log somewhere else.” It is changing the command’s file descriptors before the program starts.

Use Callable-Sentinel Iteration for Chunked Reads in Python

Fri, 04 Sep 2026 00:00:00 +0700

Reading a file in chunks is a small problem that appears in many larger tasks: hashing uploads, copying large files, parsing binary records, compressing streams, and sending data without loading everything into memory.

A common solution is a while loop that reads one chunk, checks for end-of-file, processes the chunk, and repeats. That loop is correct when written carefully, but Python has another standard-library pattern that expresses the same control flow as iteration:

Write Files Atomically on Linux with rename and fsync

Fri, 04 Sep 2026 00:00:00 +0700

Updating a small file looks simple: open it, truncate it, write the new contents, and close it. That works when nothing interrupts the write.

The failure mode appears when a process crashes, the machine loses power, or another process reads the file while it is being rewritten. A reader can observe an empty or partially written file, and a crash can leave the pathname referring to incomplete data.

For configuration files, state snapshots, generated metadata, and similar single-file updates, a better pattern is to write a complete replacement beside the original file and then rename it into place.