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#![allow(clippy::expect_used)]
#![allow(clippy::unwrap_used)]
#![allow(clippy::panic)]
#![allow(clippy::uninlined_format_args)]
#![allow(clippy::match_wild_err_arm)]
#![allow(clippy::cast_ptr_alignment)]
#![allow(clippy::doc_markdown)]
/// Visual demonstration of file descriptor reuse bug
///
/// This creates output files showing what fd numbers files receive
/// Run with: cargo run --example visual_fd_demo
use std::{fs::File, io::Write, os::unix::io::AsRawFd, process::exit};
use fork::{Fork, close_fd, fork, redirect_stdio, waitpid};
fn main() {
println!("\nRunning demonstration...\n");
demo_close_fd();
demo_redirect_stdio();
println!("═══════════════════════════════════════════════════════════════");
println!("Results written to /tmp/fd_demo_*.txt");
println!("═══════════════════════════════════════════════════════════════\n");
// Show results
show_results();
}
fn demo_close_fd() {
match fork() {
Ok(Fork::Parent(child)) => {
waitpid(child).unwrap();
}
Ok(Fork::Child) => {
// Write to file before closing stdio (so we can see output)
let mut report = File::create("/tmp/fd_demo_close_fd.txt").unwrap();
writeln!(report, "SCENARIO 1: Using close_fd()").unwrap();
writeln!(report, "══════════════════════════════════════").unwrap();
writeln!(report).unwrap();
// Close stdio
close_fd().unwrap();
writeln!(report, "After close_fd():").unwrap();
writeln!(report, " fd 0, 1, 2 are now FREE").unwrap();
writeln!(report).unwrap();
// Open test files
let f1 = File::create("/tmp/fd_demo_file1.txt").unwrap();
let f2 = File::create("/tmp/fd_demo_file2.txt").unwrap();
let f3 = File::create("/tmp/fd_demo_file3.txt").unwrap();
writeln!(report, "Opened files:").unwrap();
writeln!(
report,
" file1.txt → fd {} ⚠️ BUG: Reused stdin!",
f1.as_raw_fd()
)
.unwrap();
writeln!(
report,
" file2.txt → fd {} ⚠️ BUG: Reused stdout!",
f2.as_raw_fd()
)
.unwrap();
writeln!(
report,
" file3.txt → fd {} ⚠️ BUG: Reused stderr!",
f3.as_raw_fd()
)
.unwrap();
writeln!(report).unwrap();
writeln!(report, "DANGER:").unwrap();
writeln!(report, " - println!() would write to file2.txt").unwrap();
writeln!(report, " - panic!() would write to file3.txt").unwrap();
writeln!(report, " - Silent file corruption!").unwrap();
exit(0);
}
Err(_) => panic!("Fork failed"),
}
}
fn demo_redirect_stdio() {
match fork() {
Ok(Fork::Parent(child)) => {
waitpid(child).unwrap();
}
Ok(Fork::Child) => {
// Write to file before redirecting (so we can see output)
let mut report = File::create("/tmp/fd_demo_redirect_stdio.txt").unwrap();
writeln!(report, "SCENARIO 2: Using redirect_stdio()").unwrap();
writeln!(report, "══════════════════════════════════════").unwrap();
writeln!(report).unwrap();
// Redirect stdio to /dev/null
redirect_stdio().unwrap();
writeln!(report, "After redirect_stdio():").unwrap();
writeln!(report, " fd 0 → /dev/null").unwrap();
writeln!(report, " fd 1 → /dev/null").unwrap();
writeln!(report, " fd 2 → /dev/null").unwrap();
writeln!(report, " (fds 0,1,2 remain OCCUPIED)").unwrap();
writeln!(report).unwrap();
// Open test files
let f1 = File::create("/tmp/fd_demo_file1_safe.txt").unwrap();
let f2 = File::create("/tmp/fd_demo_file2_safe.txt").unwrap();
let f3 = File::create("/tmp/fd_demo_file3_safe.txt").unwrap();
writeln!(report, "Opened files:").unwrap();
writeln!(
report,
" file1.txt → fd {} ✅ SAFE: Higher fd!",
f1.as_raw_fd()
)
.unwrap();
writeln!(
report,
" file2.txt → fd {} ✅ SAFE: Higher fd!",
f2.as_raw_fd()
)
.unwrap();
writeln!(
report,
" file3.txt → fd {} ✅ SAFE: Higher fd!",
f3.as_raw_fd()
)
.unwrap();
writeln!(report).unwrap();
writeln!(report, "SAFETY:").unwrap();
writeln!(report, " - println!() goes to /dev/null (discarded)").unwrap();
writeln!(report, " - panic!() goes to /dev/null (discarded)").unwrap();
writeln!(report, " - Files are protected!").unwrap();
exit(0);
}
Err(_) => panic!("Fork failed"),
}
}
fn show_results() {
println!("BUG (close_fd):");
println!("───────────────────────────────────────────────────────────────");
if let Ok(content) = std::fs::read_to_string("/tmp/fd_demo_close_fd.txt") {
print!("{}", content);
}
println!("\n");
println!("FIX (redirect_stdio):");
println!("───────────────────────────────────────────────────────────────");
if let Ok(content) = std::fs::read_to_string("/tmp/fd_demo_redirect_stdio.txt") {
print!("{}", content);
}
// Cleanup
let _ = std::fs::remove_file("/tmp/fd_demo_close_fd.txt");
let _ = std::fs::remove_file("/tmp/fd_demo_redirect_stdio.txt");
let _ = std::fs::remove_file("/tmp/fd_demo_file1.txt");
let _ = std::fs::remove_file("/tmp/fd_demo_file2.txt");
let _ = std::fs::remove_file("/tmp/fd_demo_file3.txt");
let _ = std::fs::remove_file("/tmp/fd_demo_file1_safe.txt");
let _ = std::fs::remove_file("/tmp/fd_demo_file2_safe.txt");
let _ = std::fs::remove_file("/tmp/fd_demo_file3_safe.txt");
}
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