EOF(3const)

✨ EOF — the end of the road, bestie ✨

okay so this is EOF, from section 3const of the manual (the "const" girlies, we love them 💅). She lives in the Standard C library, aka libc, and she is literally the vibe of "that's all, nothing left, go home".

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🌸 NAME 🌸

EOF — end of file or error indicator 💖

she's not a character. she's a feeling. and also a number.

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📚 LIBRARY 📚

Standard C library (libc) 🫶

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📝 SYNOPSIS 📝

#include <stdio.h>

#define EOF  /* ... */

like... it exists. that's the whole pitch ✨

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💖 DESCRIPTION 💖

okay so listen. EOF represents the end of an input file, OR an error indication. either one. she's flexible like that 💅

• she is a negative value, and
• her type is int.

and here's the part that makes her so iconic: EOF is not a character. she literally can't be represented by unsigned char. she's not like the other girls — she's a sentinel value that lives outside of the valid range for valid characters 👑

so when you see her, it's not a letter, it's a signal. it's giving "this is over". it's giving "something went wrong". either way, you know 🦋

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🎀 STANDARDS 🎀

• C11
• POSIX.1-2024

certified. official. no cap ✨

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🌈 HISTORY 🌈

• C89
• POSIX.1-1988

she's been here since forever, an OG, a legacy queen 👑💜

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⚠️ CAVEATS ⚠️

right so this is the important part, bestie, pay attention 🙈

Programs can't pass this value to an output function to "write" the end of a file. not a thing. don't try it.

attempting it would likely result in undefined behavior 💀💀💀 like, actual UB. we do not do that here.

so what do you do instead? closing the writing stream, or closing the file descriptor that refers to such file — that is the way to signal the end of that file. that's it. that's the move. periodt 🫶

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👀 SEE ALSO 👀

• feof(3)
• fgetc(3)

go read those too, they're friends of hers, iykyk 🌸

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mwah 💋 this page came from the Linux man-pages 6.20, dated 2026-01-05. stan stable docs, stan accurate docs, and stan closing your file descriptors properly 🎀✨🦋