--- title: "Watch Out for Data Loss When Redirecting to a File in a Shell Script — Nick Janetakis" url: https://daily.dev/posts/watch-out-for-data-loss-when-redirecting-to-a-file-in-a-shell-script-nick-janetakis-njtpgwsqc source_url: https://nickjanetakis.com/blog/watch-out-for-data-loss-when-redirecting-to-a-file-in-a-shell-script type: article source: "Nick Janetakis" published: 2026-07-07T11:36:16.126Z updated: 2026-07-07T11:36:36.639Z tags: ["shell", "bash"] reading_time: 8 upvotes: 0 comments: 0 language: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Watch Out for Data Loss When Redirecting to a File in a Shell Script — Nick Janetakis **[Nick Janetakis](https://daily.dev/sources/nickjanetakis)** · 8 min read · 0 upvotes · 0 comments ## Summary Shell file redirection truncates the destination file immediately when a pipeline starts, before any data is written. This creates a risk of data loss if the pipeline fails midway — for example, overwriting a valid database backup with an empty or partial file. The safe pattern is to redirect output to a temporary file first, then use `mv` to atomically rename it to the final destination (ensuring both files are on the same filesystem). The post uses `strace` to verify the truncation behavior and confirm atomic renames via `renameat2` syscalls. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [The one rsync mistake that could destroy your backups](https://daily.dev/posts/the-one-rsync-mistake-that-could-destroy-your-backups-s6biwkbt9) · All Things Open · 0 upvotes · 0 comments --- Tags: [#shell](https://daily.dev/tags/shell), [#bash](https://daily.dev/tags/bash) [View this post on daily.dev](https://daily.dev/posts/watch-out-for-data-loss-when-redirecting-to-a-file-in-a-shell-script-nick-janetakis-njtpgwsqc)