--- title: Watch Out for Data Loss When Redirecting to a File in a... description: 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... canonical: https://daily.dev/posts/watch-out-for-data-loss-when-redirecting-to-a-file-in-a-shell-script-nick-janetakis-njtpgwsqc twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Watch Out for Data Loss When Redirecting to a File in a Shell Script — Nick Janetakis | daily.dev og:description: 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... og:url: https://daily.dev/posts/watch-out-for-data-loss-when-redirecting-to-a-file-in-a-shell-script-nick-janetakis-njtpgwsqc og:image: https://api.daily.dev/og/posts/NjtpgwsQc.png og:image:alt: Watch Out for Data Loss When Redirecting to a File in a Shell Script — Nick Janetakis og:image:width: 1200 og:image:height: 630 og:locale: 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 - [Redirect Multiple Commands or an Entire Script to a File — Nick Janetakis](https://daily.dev/posts/redirect-multiple-commands-or-an-entire-script-to-a-file-nick-janetakis-wjo6swtdp) · Nick Janetakis · 1 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) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"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","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/watch-out-for-data-loss-when-redirecting-to-a-file-in-a-shell-script-nick-janetakis-njtpgwsqc"},"datePublished":"2026-07-07T11:36:16.126Z","dateModified":"2026-07-07T11:36:36.639Z","description":"Shell file redirection truncates the destination file immediately when a pipeline starts, before any data is written. 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