diff --git a/completions/bash b/completions/bash
new file mode 100644
index 0000000..175a5d8
--- /dev/null
+++ b/completions/bash
@@ -0,0 +1,63 @@
+#/usr/bin/env bash
+
+_remove_opts() {
+    local opt new_opts
+    for opt in ${available_opts}; do
+        if [[ $opt != $1 && $opt != $2 ]]; then
+            new_opts+="$opt "
+        fi
+    done
+    available_opts=$new_opts
+}
+
+_doby_completion() {
+    local cur="${COMP_WORDS[COMP_CWORD]}"
+    local opts="-f --force-encrypt -i --interactive -h --help -V --version --password -t --time-cost -m --memory-cost -p --parallelism -b --block-size -c --cipher"
+    if [[ ${cur} == -* ]]; then
+        local i available_opts=$opts
+        for i in ${COMP_WORDS[@]}; do
+            if [[ ${opts[*]} =~ $i ]]; then
+                case $i in
+                    "-f"|"--force-encrypt")
+                        _remove_opts "-f" "--force-encrypt"
+                        ;;
+                    "-i"|"--interactive")
+                        _remove_opts "-i" "--interactive"
+                        ;;
+                    "-h"|"--help")
+                        _remove_opts "-h" "--help"
+                        ;;
+                    "-V"|"--version")
+                        _remove_opts "-V" "--version"
+                        ;;
+                    "--password")
+                        _remove_opts "--password"
+                        ;;
+                    "-t"|"--time-cost")
+                        _remove_opts "-t" "--time-cost"
+                        ;;
+                    "-m"|"--memory-cost")
+                        _remove_opts "-m" "--memory-cost"
+                        ;;
+                    "-p"|"--parallelism")
+                        _remove_opts "-p" "--parallelism"
+                        ;;
+                    "-b"|"--block-size")
+                        _remove_opts "-b" "--block-size"
+                        ;;
+                    "-c"|"--cipher")
+                        _remove_opts "-c" "--cipher"
+                        ;;
+                esac
+            fi
+        done
+        COMPREPLY=($(compgen -W "${available_opts}" -- "${cur}"))
+    else
+        local prev="${COMP_WORDS[COMP_CWORD-1]}"
+        if [[ ${prev} == "-c" || ${prev} == "--cipher" ]]; then
+            COMPREPLY=($(compgen -W "aes xchacha20" -- "${cur}"))
+        fi
+    fi
+}
+
+complete -F _doby_completion -o bashdefault -o default doby
\ No newline at end of file
diff --git a/completions/zsh b/completions/zsh
new file mode 100644
index 0000000..0599366
--- /dev/null
+++ b/completions/zsh
@@ -0,0 +1,19 @@
+#compdef doby
+
+function _doby {
+    _arguments \
+        '(-f --force-encrypt)'{-f,--force-encrypt}'[Encrypt even if doby format is recognized]' \
+        '(-i --interactive)'{-i,--interactive}'[Prompt before overwriting files]' \
+        '(: * -)'{-h,--help}'[Prints help information]' \
+        '(: * -)'{-V,--version}'[Prints version information]' \
+        '--password=[Password used to derive encryption keys]' \
+        '(-t --time-cost)'{-t,--time-cost}'[Argon2 time cost]' \
+        '(-m --memory-cost)'{-m,--memory-cost}'[Argon2 memory cost (in kilobytes)]' \
+        '(-p --parallelism)'{-p,--parallelism}'[Argon2 parallelism cost]' \
+        '(-b --block-size)'{-b,--block-size}'[Size of the I/O buffer (in bytes)]' \
+        '(-c --cipher)'{-c,--cipher}'[Encryption cipher to use]: :(aes xchacha20)' \
+        ':::_files' \
+        ':::_files' \
+}
+
+_doby "$@"
diff --git a/src/bin/compgen.rs b/src/bin/compgen.rs
new file mode 100644
index 0000000..a3bfb3a
--- /dev/null
+++ b/src/bin/compgen.rs
@@ -0,0 +1,17 @@
+use std::{env, io};
+use clap::Shell;
+use doby::cli;
+
+fn main() {
+    let mut args = env::args().skip(1);
+    if let Some(shell) = args.next() {
+        if let Ok(shell) = shell.parse() {
+            cli::app().gen_completions_to("doby", shell, &mut io::stdout());
+        } else {
+            eprintln!("error: invalid shell: {}", shell);
+            eprintln!("shell variants: {:?}", Shell::variants());
+        }
+    } else {
+        eprintln!("usage: compgen <shell>");
+    }
+}
\ No newline at end of file
diff --git a/src/cli.rs b/src/cli.rs
index ca2a1a8..09e6c9f 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -31,8 +31,8 @@ impl From<CliArgs> for ParseResult {
     }
 }
 
-pub fn parse() -> Option<ParseResult> {
-    let app = App::new(crate_name!())
+pub fn app<'a>() -> App<'a, 'a> {
+    App::new(crate_name!())
         .version(crate_version!())
         .setting(AppSettings::ColoredHelp)
         .about("Secure symmetric encryption from the command line.")
@@ -42,7 +42,7 @@ pub fn parse() -> Option<ParseResult> {
             Arg::with_name("1_force_encrypt")
                 .short("f")
                 .long("force-encrypt")
-                .help(&format!("Encrypt even if {} format is recognized", crate_name!()))
+                .help(concat!("Encrypt even if ", crate_name!(), " format is recognized"))
         )
         .arg(
             Arg::with_name("2_interactive")
@@ -97,7 +97,10 @@ pub fn parse() -> Option<ParseResult> {
                 .possible_values(&["aes", "xchacha20"])
                 .case_insensitive(true)
         )
-        .get_matches();
+}
+
+pub fn parse() -> Option<ParseResult> {
+    let app = app().get_matches();
 
     let params = {
         let t_cost = number(app.value_of("2_t_cost").unwrap())?;