diff --git a/Cargo.toml b/Cargo.toml
index bf6b76d7..9ea95766 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -30,6 +30,7 @@ pam-sys = "0.5"
 pin-utils = "0.1.0-alpha"
 proxmox = { git = "ssh://gitolite3@proxdev.maurer-it.com/rust/proxmox", version = "0.1", features = [ "sortable-macro", "api-macro" ] }
 regex = "1.0"
+rustyline = "5.0.4"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 shellwords = "1.0"
diff --git a/src/bin/completion.rs b/src/bin/completion.rs
new file mode 100644
index 00000000..754c674e
--- /dev/null
+++ b/src/bin/completion.rs
@@ -0,0 +1,72 @@
+use failure::*;
+use serde_json::Value;
+
+use proxmox::{sortable, identity};
+use proxmox::api::*;
+use proxmox::api::schema::*;
+
+use proxmox_backup::cli::*;
+
+#[sortable]
+const API_METHOD_TEST_COMMAND: ApiMethod = ApiMethod::new(
+    &ApiHandler::Sync(&test_command),
+    &ObjectSchema::new(
+        "Test command.",
+        &sorted!([
+            ( "verbose", true, &BooleanSchema::new("Verbose output.").schema() ),
+        ])
+    )
+);
+
+fn test_command(
+    _param: Value,
+    _info: &ApiMethod,
+    _rpcenv: &mut dyn RpcEnvironment,
+) -> Result<Value, Error> {
+
+
+    Ok(Value::Null)
+}
+
+fn command_map() -> CliCommandMap {
+    let cmd_def = CliCommandMap::new()
+        .insert("ls", CliCommand::new(&API_METHOD_TEST_COMMAND).into())
+        .insert("test", CliCommand::new(&API_METHOD_TEST_COMMAND).into())
+        .insert("help", help_command_def().into());
+
+    cmd_def
+}
+
+
+fn main() -> Result<(), Error> {
+
+    let def = CommandLineInterface::Nested(command_map());
+
+    let helper = CliHelper::new(def);
+
+    let config = rustyline::config::Builder::new()
+    //.completion_type(rustyline::config::CompletionType::List)
+    //.completion_prompt_limit(0)
+        .build();
+
+    let mut rl = rustyline::Editor::<CliHelper>::with_config(config);
+    rl.set_helper(Some(helper));
+
+    while let Ok(line) = rl.readline("# prompt: ") {
+        let helper = rl.helper().unwrap();
+        // readline already handles tabs, so here we only split on spaces
+        let args = shellword_split(&line)?;
+
+        let def = helper.cmd_def();
+        let _ = match def {
+            CommandLineInterface::Simple(ref cli_cmd) => {
+                handle_simple_command(def, "", &cli_cmd, args)
+            }
+            CommandLineInterface::Nested(ref map) => {
+                handle_nested_command(def, "", &map, args)
+            }
+        };
+    }
+
+    Ok(())
+}
diff --git a/src/cli.rs b/src/cli.rs
index 02ad6a61..9a5ccd9b 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -10,6 +10,9 @@ pub use environment::*;
 mod format;
 pub use format::*;
 
+mod completion;
+pub use completion::*;
+
 mod getopts;
 pub use getopts::*;
 
diff --git a/src/cli/completion.rs b/src/cli/completion.rs
new file mode 100644
index 00000000..59d171bf
--- /dev/null
+++ b/src/cli/completion.rs
@@ -0,0 +1,230 @@
+use failure::*;
+
+use rustyline::completion::*;
+
+use super::*;
+
+#[derive(PartialEq)]
+enum ParseMode {
+    Space,
+    DoubleQuote,
+    EscapeNormal,
+    EscapeInDoubleQuote,
+    Normal,
+    SingleQuote,
+}
+
+/// Parsing strings as they would be interpreted by the UNIX Bourne shell.
+///
+/// - ``finalize``: assume this is a complete command line. Set this
+///   to false for the 'completion' helper, which needs to get
+///   information about the last unfinished parameter.
+///
+/// Returns the list of fully parsed words (unescaped and quotes
+/// removed). If there are unclosed quotes, the start of that
+/// parameter, the parameter value (unescaped and quotes removed), and
+/// the quote type are returned.
+pub fn shellword_split_unclosed(s: &str, finalize: bool) -> (Vec<String>, Option<(usize, String, Quote)>) {
+
+    let char_indices = s.char_indices();
+    let mut args: Vec<String> = Vec::new();
+    let mut field_start = None;
+    let mut field = String::new();
+    let mut mode = ParseMode::Space;
+
+    let space_chars = [' ', '\t', '\n'];
+
+    for (index, c) in char_indices {
+        match mode {
+            ParseMode::Space => {
+                if c == '"' {
+                    mode = ParseMode::DoubleQuote;
+                    field_start = Some((index, Quote::Double));
+                } else if c == '\\' {
+                    mode = ParseMode::EscapeNormal;
+                    field_start = Some((index, Quote::None));
+                } else if c == '\'' {
+                    mode = ParseMode::SingleQuote;
+                    field_start = Some((index, Quote::Single));
+                } else if space_chars.iter().any(|s| c == *s) {
+                    /* skip space */
+                } else {
+                    mode = ParseMode::Normal;
+                    field_start = Some((index, Quote::None));
+                    field.push(c);
+                }
+            }
+            ParseMode::EscapeNormal => {
+                mode = ParseMode::Normal;
+                field.push(c);
+            }
+            ParseMode::EscapeInDoubleQuote => {
+                // Within double quoted strings, backslashes are only
+                // treated as metacharacters when followed by one of
+                // the following characters: $ ' " \ newline
+                if c == '$' || c == '\'' || c == '"' || c == '\\' || c == '\n' {
+                     field.push(c);
+                } else {
+                    field.push('\\');
+                    field.push(c);
+                }
+                mode = ParseMode::DoubleQuote;
+            }
+            ParseMode::Normal => {
+                if c == '"' {
+                    mode = ParseMode::DoubleQuote;
+                } else if c == '\'' {
+                     mode = ParseMode::SingleQuote;
+                } else if c == '\\' {
+                    mode = ParseMode::EscapeNormal;
+                } else if space_chars.iter().any(|s| c == *s) {
+                    mode = ParseMode::Space;
+                    let (_start, _quote) = field_start.take().unwrap();
+                    args.push(field.split_off(0));
+                } else {
+                    field.push(c); // continue
+                }
+            }
+            ParseMode::DoubleQuote => {
+                if c == '"' {
+                    mode = ParseMode::Normal;
+                } else if c == '\\' {
+                    mode = ParseMode::EscapeInDoubleQuote;
+                } else {
+                   field.push(c); // continue
+                }
+            }
+            ParseMode::SingleQuote => {
+                // Note: no escape in single quotes
+                if c == '\'' {
+                    mode = ParseMode::Normal;
+                }  else {
+                    field.push(c); // continue
+                }
+            }
+        }
+    }
+
+    if finalize && mode == ParseMode::Normal {
+        let (_start, _quote) = field_start.take().unwrap();
+        args.push(field.split_off(0));
+    }
+
+    match field_start {
+        Some ((start, quote)) => {
+            (args, Some((start, field, quote)))
+        }
+        None => {
+            (args, None)
+        }
+    }
+}
+
+/// Splits a string into a vector of words in the same way the UNIX Bourne shell does.
+///
+/// Return words unescaped and without quotes.
+pub fn shellword_split(s: &str) -> Result<Vec<String>, Error> {
+
+    let (args, unclosed_field) = shellword_split_unclosed(s, true);
+    if !unclosed_field.is_none() {
+        bail!("shellword split failed - found unclosed quote.");
+    }
+    Ok(args)
+}
+
+#[test]
+fn test_shellword_split() {
+
+    let expect = [ "ls", "/etc" ];
+    let expect: Vec<String> = expect.iter().map(|v| v.to_string()).collect();
+
+    assert_eq!(expect, shellword_split("ls /etc").unwrap());
+    assert_eq!(expect, shellword_split("ls \"/etc\"").unwrap());
+    assert_eq!(expect, shellword_split("ls '/etc'").unwrap());
+    assert_eq!(expect, shellword_split("ls '/etc'").unwrap());
+
+    assert_eq!(expect, shellword_split("ls /e\"t\"c").unwrap());
+    assert_eq!(expect, shellword_split("ls /e'tc'").unwrap());
+    assert_eq!(expect, shellword_split("ls /e't''c'").unwrap());
+
+    let expect = [ "ls", "/etc 08x" ];
+    let expect: Vec<String> = expect.iter().map(|v| v.to_string()).collect();
+    assert_eq!(expect, shellword_split("ls /etc\\ \\08x").unwrap());
+
+    let expect = [ "ls", "/etc \\08x" ];
+    let expect: Vec<String> = expect.iter().map(|v| v.to_string()).collect();
+    assert_eq!(expect, shellword_split("ls \"/etc \\08x\"").unwrap());
+}
+
+#[test]
+fn test_shellword_split_unclosed() {
+
+    let expect = [ "ls".to_string() ].to_vec();
+    assert_eq!(
+        (expect, Some((3, "./File1 name with spaces".to_string(), Quote::Single))),
+        shellword_split_unclosed("ls './File1 name with spaces", false)
+    );
+
+    let expect = [ "ls".to_string() ].to_vec();
+    assert_eq!(
+        (expect, Some((3, "./File2 name with spaces".to_string(), Quote::Double))),
+        shellword_split_unclosed("ls \"./File2 \"name\" with spaces", false)
+    );
+}
+
+pub struct CliHelper {
+    cmd_def:  CommandLineInterface,
+}
+
+impl CliHelper {
+
+    pub fn new(cmd_def: CommandLineInterface) -> Self {
+        Self { cmd_def }
+    }
+
+    pub fn cmd_def(&self) -> &CommandLineInterface {
+        &self.cmd_def
+    }
+}
+
+impl rustyline::completion::Completer for CliHelper {
+    type Candidate = String;
+
+    fn complete(
+        &self,
+        line: &str,
+        pos: usize,
+        _ctx: &rustyline::Context<'_>,
+    ) -> rustyline::Result<(usize, Vec<Self::Candidate>)> {
+
+        let line = &line[..pos];
+
+        let (args, start ) = match shellword_split_unclosed(line, false) {
+            (mut args, None) => {
+                args.push("".into());
+                (args, pos)
+            }
+            (mut args, Some((start , arg, _quote))) => {
+                args.push(arg);
+                (args, start)
+            }
+        };
+
+        let def = &self.cmd_def;
+
+        let completions = if !args.is_empty() && args[0] == "help" {
+            get_help_completion(&def, &help_command_def(), &args[1..])
+        } else {
+            get_nested_completion(&def, &args)
+        };
+
+        return Ok((start, completions));
+    }
+}
+
+impl rustyline::hint::Hinter for CliHelper {}
+impl rustyline::highlight::Highlighter for CliHelper {}
+
+impl rustyline::Helper for CliHelper {
+
+}