@seungjoo

Seung Joo Ahn

@seungjoo

Backend Engineer

Seoul, South KoreaJoined January 2025

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Seung Joo Ahn's blogs

frog's devlogfrogsdevlog.hashnode.dev7 posts

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[Day 8] Linux Pipes Are Just Plumbing — And I Already Had the Wrenches

2d ago · 8 min read · Day 7 ended with a real shift in how I think about sockets. The kernel owns them. Processes just hold pickup tickets. accept() isn't accepting — it's picking up what the kernel already prepared. Today

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[Day 7] The Process Went to Sleep — and the Kernel Kept Working

3d ago · 12 min read · In Day 6, I watched a single connection arrive at the server and saw two fds show up instead of one. The listening socket (fd 3) stayed at the door, and a new connected socket (fd 4) was created for t

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SJSeung Joo Ahnfrogsdevlog.hashnode.dev

[Day 6] A Connection Came In — and a New fd Appeared

4d ago · 10 min read · Yesterday in Day 5, while digging into why rm doesn't immediately reclaim disk space, I wrote this line: "Files, pipes, sockets — they're all fds." But that was just words. The only thing I actually

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[Day 5] I Ran rm, So Why Isn't the Disk Space Back?

5d ago · 7 min read · After Day 4 on fork/exec/file descriptors/pipes, one thing still nagged me. In that post I wrote: "The child duplicates that fd onto fd 1 with dup2(3, 1) — then closes the original fd 3." Why close

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[Day 4] Why ls Doesn't Know Where Its Output Goes

Apr 16 · 6 min read · After typing ls > out.txt hundreds of times, a strange question hit me: Does ls somehow detect that its output is being redirected? Does it have some logic like "oh, output is going to a file now, let

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Seung Joo Ahn

About

Available for

Seung Joo Ahn's blogs

Recently published

[Day 8] Linux Pipes Are Just Plumbing — And I Already Had the Wrenches

[Day 7] The Process Went to Sleep — and the Kernel Kept Working

[Day 6] A Connection Came In — and a New fd Appeared

[Day 5] I Ran rm, So Why Isn't the Disk Space Back?

[Day 4] Why ls Doesn't Know Where Its Output Goes

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Seung Joo Ahn

About

Available for

Seung Joo Ahn's blogs

Recently published

[Day 8] Linux Pipes Are Just Plumbing — And I Already Had the Wrenches

[Day 7] The Process Went to Sleep — and the Kernel Kept Working

[Day 6] A Connection Came In — and a New fd Appeared

[Day 5] I Ran rm, So Why Isn't the Disk Space Back?

[Day 4] Why ls Doesn't Know Where Its Output Goes