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--- eof [February 18, 2026 at 01:32] – created yanevskiv
+++ eof [May 14, 2026 at 11:38] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
+# EOF
+**EOF** is an acronym that stands for "End of file"
+## Shell
+In shell, EOF is commonly used as a terminator in what is called a [heredoc](https://en.wikipedia.org/wiki/Here_document) ("here document").
+It's when you want to supply a multiline text to a command to its standard output, using `<<`.
+```
+ $ cat > hello.txt << EOF
+Here, you can write anything you like.
+It's not over until you actually type E-O-F.
+You can cancel with Ctrl + C.
+EOF
+```
+But this is just a convention. You can use any string you like in heredocs.
+```
+ $ cat > hello.txt << whatever
+Now you can type EOF EOF EOF as much as you want
+until you type it
+whatever
+```
+## C
+In C programming language, EOF is a constant defined `-1` which indicates an end of file.
+```c
+// Compile: gcc main.c -o program
+// Run:     echo 'Hello world' | ./program
+// Output:  HELLO WORLD
+#include <stdio.h>
+#include <ctype.h>
+int main()
+{
+    int ch;
+    while ((ch = fgetc(stdin)) != EOF) {
+        putchar(toupper(ch));
+    }
+    return 0;
+}
+```
+## Links
+ - https://en.wikipedia.org/wiki/End-of-file
+ - https://stackoverflow.com/questions/1782080/what-is-eof-in-the-c-programming-language