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use procfs::process::{all_processes, Stat};
struct ProcessEntry {
stat: Stat,
cmdline: Option<Vec<String>>,
}
/// Print all processes as a tree.
/// The tree reflects the hierarchical relationship between parent and child processes.
fn main() {
// Get all processes
let processes: Vec<ProcessEntry> = match all_processes() {
Err(err) => {
println!("Failed to read all processes: {}", err);
return;
}
Ok(processes) => processes,
}
.filter_map(|v| {
v.and_then(|p| {
let stat = p.stat()?;
let cmdline = p.cmdline().ok();
Ok(ProcessEntry { stat, cmdline })
})
.ok()
})
.collect();
// Iterate through all processes and start with top-level processes.
// Those can be identified by checking if their parent PID is zero.
for process in &processes {
if process.stat.ppid == 0 {
print_process(process, &processes, 0);
}
}
}
/// Take a process, print its command and recursively list all child processes.
/// This function will call itself until no further children can be found.
/// It's a depth-first tree exploration.
///
/// depth: The hierarchical depth of the process
fn print_process(process: &ProcessEntry, all_processes: &Vec<ProcessEntry>, depth: usize) {
let cmdline = match &process.cmdline {
Some(cmdline) => cmdline.join(" "),
None => "zombie process".into(),
};
// Some processes seem to have an empty cmdline.
if cmdline.is_empty() {
return;
}
// 10 characters width for the pid
let pid_length = 8;
let mut pid = process.stat.pid.to_string();
pid.push_str(&" ".repeat(pid_length - pid.len()));
let padding = " ".repeat(4 * depth);
println!("{}{}{}", pid, padding, cmdline);
let children = get_children(process.stat.pid, all_processes);
for child in &children {
print_process(child, all_processes, depth + 1);
}
}
/// Get all children of a specific process, by iterating through all processes and
/// checking their parent pid.
fn get_children(pid: i32, all_processes: &[ProcessEntry]) -> Vec<&ProcessEntry> {
all_processes
.iter()
.filter(|process| process.stat.ppid == pid)
.collect()
}
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