Count newline characters.
Count newline bytes in a C file while retaining EOF as an int.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
#include <limits.h>
int main(void) {
FILE *file = fopen("notes.txt", "r");
if (!file) return 1;
int ch; size_t lines = 0;
while ((ch = fgetc(file)) != EOF) if (ch == '\n') ++lines;
int failed = ferror(file);
if (fclose(file) != 0) failed = 1;
if (failed) return 1;
printf("%zu\n", lines);
return 0;
}Expected output EXAMPLE
2
Details
Save as snippet.c. Compile with gcc -std=c17 -Wall -Wextra snippet.c -o snippet, then run ./snippet. Uses the C standard library.
A final line without a newline is not counted.
Tested on Ubuntu 24.04.5 LTS · · gcc (Ubuntu 13.3.0-6ubuntu2~24.04.1) 13.3.0 · gcc 4:13.2.0-7ubuntu1
Test inputs, results and environment
The exact published code ran in a dedicated Linux test container with prepared inputs. Unprivileged snippet process, external networking disabled, read-only root filesystem, and a fresh temporary working directory. Fixtures and output records are isolated from the application database. Testing covers this example and its stated checks, not every input, operating system, or runtime version. The Linux container shares its host's kernel; this is not a native Windows test.
- Architecture / host kernel
- x86_64 / 6.18.54.1-microsoft-standard-WSL2
- Snippet identity / locale
- uid=65534, gid=65534 (unprivileged) / C.UTF-8
- Interpreter invocation
gcc -std=c17 -Wall -Wextra -Werror snippet.c -lm -o snippet && ./snippet- Container image ID
sha256:32dc2d998158b6554c99b73b533f423696a0f3e31e8cbea9db10b5eee9a2fadd- Code SHA-256
5a06f447f933b57eaf143c6881f510f6b3eb0ad37bdd5f9c611ca6cc55426794- Dependencies
- gcc 4:13.2.0-7ubuntu1
Test input setup
These are the prepared inputs used by the test harness. See Details above for the prerequisites and how to run this example.
printf 'one\ntwo\n' > notes.txt
Observed standard output
2
Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.