Vendor dependencies

Let's see how I like this workflow.

vendor/procfs/examples/process_hierarchy.rs

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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()
+}