diff --git a/src/od/od.rs b/src/od/od.rs
index d98f8eaac..99056985d 100644
--- a/src/od/od.rs
+++ b/src/od/od.rs
@@ -84,7 +84,7 @@ pub fn uumain(args: Vec<String>) -> i32 {
     opts.optflagmulti("f", "", "floating point single precision (32-bit) units");
     opts.optflagmulti("F", "", "floating point double precision (64-bit) units");
 
-    opts.optopt("t", "format", "select output format or formats", "TYPE");
+    opts.optmulti("t", "format", "select output format or formats", "TYPE");
     opts.optflag("v", "output-duplicates", "do not use * to mark line suppression");
     opts.optflagopt("w", "width",
                 ("output BYTES bytes per output line. 32 is implied when BYTES is not \
@@ -146,7 +146,13 @@ pub fn uumain(args: Vec<String>) -> i32 {
         inputs.push(InputSource::Stdin);
     }
 
-    let formats = parse_format_flags(&args);
+    let formats = match parse_format_flags(&args) {
+        Ok(f) => f,
+        Err(e) => {
+            disp_err!("{}", e);
+            return 1;
+        }
+    };
 
     let mut line_bytes = match matches.opt_default("w", "32") {
         None => 16,
diff --git a/src/od/parse_formats.rs b/src/od/parse_formats.rs
index 00ddce0ee..5682e0ac2 100644
--- a/src/od/parse_formats.rs
+++ b/src/od/parse_formats.rs
@@ -24,10 +24,8 @@ macro_rules! hashmap {
 /// arguments with parameters like -w16 can only appear at the end: -fvoxw16
 /// parameters of -t/--format specify 1 or more formats.
 /// if -- appears on the commandline, parsing should stop.
-pub fn parse_format_flags(args: &Vec<String>) -> Vec<FormatterItemInfo> {
-    // Gather up format flags, we don't use getopts becase we need keep them in order.
+pub fn parse_format_flags(args: &Vec<String>) -> Result<Vec<FormatterItemInfo>, String> {
 
-    // TODO: -t fmts
     let known_formats = hashmap![
     'a' => FORMAT_ITEM_A,
     'B' => FORMAT_ITEM_OCT16,
@@ -57,38 +55,240 @@ pub fn parse_format_flags(args: &Vec<String>) -> Vec<FormatterItemInfo> {
 
     // args[0] is the name of the binary
     let mut arg_iter = args.iter().skip(1);
+    let mut expect_type_string = false;
 
     while let Some(arg) = arg_iter.next() {
-        if arg.starts_with("--") {
+        if expect_type_string {
+            match parse_type_string(arg) {
+                Ok(v) => formats.extend(v.into_iter()),
+                Err(e) => return Err(e),
+            }
+            expect_type_string = false;
+        }
+        else if arg.starts_with("--") {
             if arg.len() == 2 {
                 break;
             }
+            if arg.starts_with("--format=") {
+                let params: String = arg.chars().skip_while(|c| *c != '=').skip(1).collect();
+                match parse_type_string(&params) {
+                    Ok(v) => formats.extend(v.into_iter()),
+                    Err(e) => return Err(e),
+                }
+            }
+            if arg == "--format" {
+                expect_type_string = true;
+            }
         }
         else if arg.starts_with("-") {
             let mut flags = arg.chars().skip(1);
+            let mut format_spec = String::new();
             while let Some(c) = flags.next() {
-                if ignored_arg_opts.contains(&c) {
+                if expect_type_string {
+                    format_spec.push(c);
+                }
+                else if ignored_arg_opts.contains(&c) {
                     break;
                 }
-                match known_formats.get(&c) {
-                    None => {} // not every option is a format
-                    Some(r) => {
-                        formats.push(*r)
+                else if c=='t' {
+                    expect_type_string = true;
+                }
+                else {
+                    match known_formats.get(&c) {
+                        None => {} // not every option is a format
+                        Some(r) => {
+                            formats.push(*r)
+                        }
                     }
                 }
             }
+            if !format_spec.is_empty() {
+                match parse_type_string(&format_spec) {
+                    Ok(v) => formats.extend(v.into_iter()),
+                    Err(e) => return Err(e),
+                }
+                expect_type_string = false;
+            }
         }
     }
+    if expect_type_string {
+        return Err(format!("missing format specification after '--format' / '-t'"));
+    }
 
     if formats.is_empty() {
         formats.push(FORMAT_ITEM_OCT16); // 2 byte octal is the default
     }
 
-    formats
+    Ok(formats)
+}
+
+#[derive(PartialEq, Eq, Debug)]
+enum ParseState {
+    ExpectSize,     // expect optional size character like L for long.
+    ExpectDecimal,  // expect optional additional digits, like for 16.
+    ExpectDump,     // expect optional 'z'.
+    Finished        // no more characters may appear.
+}
+
+fn parse_type_string(params: &String) -> Result<Vec<FormatterItemInfo>, String> {
+
+    let type_chars: HashSet<_> = ['a', 'c'].iter().cloned().collect();
+    let type_ints: HashSet<_> = ['d', 'o', 'u', 'x'].iter().cloned().collect();
+    let type_floats: HashSet<_> = ['f'].iter().cloned().collect();
+    let type_all: HashSet<_> =
+            type_chars.iter()
+            .chain(type_ints.iter())
+            .chain(type_floats.iter())
+            .collect();
+
+    let mut formats = Vec::new();
+
+    // first split a type string into parts refering a single type
+    let mut type_parts = Vec::new();
+    let mut s = String::new();
+    for c in params.chars() {
+        if type_all.contains(&c) {
+            if !s.is_empty() {
+                type_parts.push(s);
+                s = String::new();
+            }
+            s.push(c);
+        }
+        else {
+            if s.is_empty() {
+                return Err(format!("unexpected char '{}' in format specification '{}'", c, params));
+            }
+            s.push(c);
+        }
+    }
+    if !s.is_empty() {
+        type_parts.push(s);
+    }
+
+    for format_type in type_parts.iter() {
+        let mut chars=format_type.chars();
+
+        let type_char = chars.next().unwrap();
+
+        let mut parse_state = ParseState::ExpectSize;
+        let mut decimal_size = String::new();
+        let mut byte_size = 0u8;
+        let mut show_ascii_dump = false;
+
+        if type_chars.contains(&type_char) {
+            parse_state = ParseState::ExpectDump;
+        }
+
+        loop {
+            match chars.next() {
+                None => break,
+                Some('z') if parse_state != ParseState::Finished => {
+                    show_ascii_dump = true;
+                    parse_state = ParseState::Finished;
+                },
+                Some(d) if d.is_digit(10)
+                        && (parse_state == ParseState::ExpectSize || parse_state == ParseState::ExpectDecimal) => {
+                    decimal_size.push(d);
+                    parse_state = ParseState::ExpectDecimal;
+                },
+
+                Some('C') if type_ints.contains(&type_char) && parse_state == ParseState::ExpectSize => {
+                    byte_size = 1;
+                    parse_state = ParseState::ExpectDump;
+                },
+                Some('S') if type_ints.contains(&type_char) && parse_state == ParseState::ExpectSize => {
+                    byte_size = 2;
+                    parse_state = ParseState::ExpectDump;
+                },
+                Some('I') if type_ints.contains(&type_char) && parse_state == ParseState::ExpectSize => {
+                    byte_size = 4;
+                    parse_state = ParseState::ExpectDump;
+                },
+                Some('L') if type_ints.contains(&type_char) && parse_state == ParseState::ExpectSize => {
+                    byte_size = 8;
+                    parse_state = ParseState::ExpectDump;
+                },
+
+                Some('F') if type_char == 'f' && parse_state == ParseState::ExpectSize => {
+                    byte_size = 4;
+                    parse_state = ParseState::ExpectDump;
+                },
+                Some('D') if type_char == 'f' && parse_state == ParseState::ExpectSize => {
+                    byte_size = 8;
+                    parse_state = ParseState::ExpectDump;
+                },
+                // Some('L') if type_char == 'f' => byte_size = 16, // TODO support f128
+
+                Some(c) => {
+                    return Err(format!("unexpected char '{}' in format specification '{}'", c, format_type));
+                }
+            }
+        }
+
+        if !decimal_size.is_empty() {
+            byte_size=match decimal_size.parse() {
+                Err(_) => return Err(format!("invalid number '{}' in format specification '{}'", decimal_size, format_type)),
+                Ok(n) => n,
+            }
+        }
+
+        match type_char {
+            'a' => formats.push(FORMAT_ITEM_A),
+            'c' => formats.push(FORMAT_ITEM_C),
+            'd' => {
+                formats.push(match byte_size {
+                    1 => FORMAT_ITEM_DEC8S,
+                    2 => FORMAT_ITEM_DEC16S,
+                    4|0 => FORMAT_ITEM_DEC32S,
+                    8 => FORMAT_ITEM_DEC64S,
+                    _ => return Err(format!("invalid size '{}' in format specification '{}'", byte_size, format_type)),
+                });
+            },
+            'o' => {
+                formats.push(match byte_size {
+                    1 => FORMAT_ITEM_OCT8,
+                    2 => FORMAT_ITEM_OCT16,
+                    4|0 => FORMAT_ITEM_OCT32,
+                    8 => FORMAT_ITEM_OCT64,
+                    _ => return Err(format!("invalid size '{}' in format specification '{}'", byte_size, format_type)),
+                });
+            },
+            'u' => {
+                formats.push(match byte_size {
+                    1 => FORMAT_ITEM_DEC8U,
+                    2 => FORMAT_ITEM_DEC16U,
+                    4|0 => FORMAT_ITEM_DEC32U,
+                    8 => FORMAT_ITEM_DEC64U,
+                    _ => return Err(format!("invalid size '{}' in format specification '{}'", byte_size, format_type)),
+                });
+            },
+            'x' => {
+                formats.push(match byte_size {
+                    1 => FORMAT_ITEM_HEX8,
+                    2 => FORMAT_ITEM_HEX16,
+                    4|0 => FORMAT_ITEM_HEX32,
+                    8 => FORMAT_ITEM_HEX64,
+                    _ => return Err(format!("invalid size '{}' in format specification '{}'", byte_size, format_type)),
+                });
+            },
+            'f' => {
+                formats.push(match byte_size {
+                    4|0 => FORMAT_ITEM_F32,
+                    8 => FORMAT_ITEM_F64,
+                    _ => return Err(format!("invalid size '{}' in format specification '{}'", byte_size, format_type)),
+                });
+            },
+            _ => unreachable!(),
+        }
+
+        if show_ascii_dump { /*TODO*/ }
+    }
+
+    Ok(formats)
 }
 
 #[allow(dead_code)]
-pub fn parse_format_flags_str(args_str: &Vec<&'static str>) -> Vec<FormatterItemInfo> {
+pub fn parse_format_flags_str(args_str: &Vec<&'static str>) -> Result<Vec<FormatterItemInfo>, String> {
     let args = args_str.iter().map(|s| s.to_string()).collect();
     parse_format_flags(&args)
 }
@@ -96,48 +296,188 @@ pub fn parse_format_flags_str(args_str: &Vec<&'static str>) -> Vec<FormatterItem
 #[test]
 fn test_no_options() {
     assert_eq!(parse_format_flags_str(
-        &vec!("od")),
+        &vec!("od")).unwrap(),
         vec!(FORMAT_ITEM_OCT16));
 }
 
 #[test]
 fn test_one_option() {
     assert_eq!(parse_format_flags_str(
-        &vec!("od", "-F")),
+        &vec!("od", "-F")).unwrap(),
         vec!(FORMAT_ITEM_F64));
 }
 
 #[test]
 fn test_two_separate_options() {
     assert_eq!(parse_format_flags_str(
-        &vec!("od", "-F", "-x")),
+        &vec!("od", "-F", "-x")).unwrap(),
         vec!(FORMAT_ITEM_F64, FORMAT_ITEM_HEX16));
 }
 
 #[test]
 fn test_two_combined_options() {
    assert_eq!(parse_format_flags_str(
-       &vec!("od", "-Fx")),
+       &vec!("od", "-Fx")).unwrap(),
        vec!(FORMAT_ITEM_F64, FORMAT_ITEM_HEX16));
 }
 
 #[test]
 fn test_ignore_non_format_parameters() {
    assert_eq!(parse_format_flags_str(
-       &vec!("od", "-d", "-Ax")),
+       &vec!("od", "-d", "-Ax")).unwrap(),
        vec!(FORMAT_ITEM_DEC16U));
 }
 
 #[test]
 fn test_ignore_separate_parameters() {
    assert_eq!(parse_format_flags_str(
-       &vec!("od", "-I", "-A", "x")),
+       &vec!("od", "-I", "-A", "x")).unwrap(),
        vec!(FORMAT_ITEM_DEC64S));
 }
 
 #[test]
 fn test_ignore_trailing_vals() {
    assert_eq!(parse_format_flags_str(
-       &vec!("od", "-D", "--", "-x")),
+       &vec!("od", "-D", "--", "-x")).unwrap(),
        vec!(FORMAT_ITEM_DEC32U));
 }
+
+#[test]
+fn test_invalid_long_format() {
+    parse_format_flags_str(&vec!("od", "--format=X")).unwrap_err();
+    parse_format_flags_str(&vec!("od", "--format=xX")).unwrap_err();
+    parse_format_flags_str(&vec!("od", "--format=aC")).unwrap_err();
+    parse_format_flags_str(&vec!("od", "--format=fI")).unwrap_err();
+    parse_format_flags_str(&vec!("od", "--format=xD")).unwrap_err();
+
+    parse_format_flags_str(&vec!("od", "--format=xC1")).unwrap_err();
+    parse_format_flags_str(&vec!("od", "--format=x1C")).unwrap_err();
+    parse_format_flags_str(&vec!("od", "--format=xz1")).unwrap_err();
+    parse_format_flags_str(&vec!("od", "--format=xzC")).unwrap_err();
+    parse_format_flags_str(&vec!("od", "--format=xzz")).unwrap_err();
+    parse_format_flags_str(&vec!("od", "--format=xCC")).unwrap_err();
+
+    parse_format_flags_str(&vec!("od", "--format=c1")).unwrap_err();
+    parse_format_flags_str(&vec!("od", "--format=x256")).unwrap_err();
+    parse_format_flags_str(&vec!("od", "--format=d5")).unwrap_err();
+    parse_format_flags_str(&vec!("od", "--format=f2")).unwrap_err();
+}
+
+#[test]
+fn test_long_format_a() {
+   assert_eq!(parse_format_flags_str(
+       &vec!("od", "--format=a")).unwrap(),
+       vec!(FORMAT_ITEM_A));
+}
+
+#[test]
+fn test_long_format_cz() {
+   assert_eq!(parse_format_flags_str(
+       &vec!("od", "--format=cz")).unwrap(),
+       vec!(FORMAT_ITEM_C)); // TODO 'z'
+}
+
+#[test]
+fn test_long_format_d() {
+   assert_eq!(parse_format_flags_str(
+       &vec!("od", "--format=d8")).unwrap(),
+       vec!(FORMAT_ITEM_DEC64S));
+}
+
+#[test]
+fn test_long_format_d_default() {
+   assert_eq!(parse_format_flags_str(
+       &vec!("od", "--format=d")).unwrap(),
+       vec!(FORMAT_ITEM_DEC32S));
+}
+
+#[test]
+fn test_long_format_o_default() {
+   assert_eq!(parse_format_flags_str(
+       &vec!("od", "--format=o")).unwrap(),
+       vec!(FORMAT_ITEM_OCT32));
+}
+
+#[test]
+fn test_long_format_u_default() {
+   assert_eq!(parse_format_flags_str(
+       &vec!("od", "--format=u")).unwrap(),
+       vec!(FORMAT_ITEM_DEC32U));
+}
+
+#[test]
+fn test_long_format_x_default() {
+   assert_eq!(parse_format_flags_str(
+       &vec!("od", "--format=x")).unwrap(),
+       vec!(FORMAT_ITEM_HEX32));
+}
+
+#[test]
+fn test_long_format_f_default() {
+   assert_eq!(parse_format_flags_str(
+       &vec!("od", "--format=f")).unwrap(),
+       vec!(FORMAT_ITEM_F32));
+}
+
+#[test]
+fn test_long_format_next_arg() {
+   assert_eq!(parse_format_flags_str(
+       &vec!("od", "--format", "f8")).unwrap(),
+       vec!(FORMAT_ITEM_F64));
+}
+
+#[test]
+fn test_short_format_next_arg() {
+   assert_eq!(parse_format_flags_str(
+       &vec!("od", "-t", "x8")).unwrap(),
+       vec!(FORMAT_ITEM_HEX64));
+}
+
+#[test]
+fn test_short_format_combined_arg() {
+   assert_eq!(parse_format_flags_str(
+       &vec!("od", "-tu8")).unwrap(),
+       vec!(FORMAT_ITEM_DEC64U));
+}
+
+#[test]
+fn test_format_next_arg_invalid() {
+    parse_format_flags_str(&vec!("od", "--format", "-v")).unwrap_err();
+    parse_format_flags_str(&vec!("od", "--format")).unwrap_err();
+    parse_format_flags_str(&vec!("od", "-t", "-v")).unwrap_err();
+    parse_format_flags_str(&vec!("od", "-t")).unwrap_err();
+}
+
+
+#[test]
+fn test_mixed_formats() {
+   assert_eq!(parse_format_flags_str(
+       &vec!(
+           "od",
+           "--skip-bytes=2",
+           "-vItu1z",
+           "-N",
+           "1000",
+           "-xt",
+           "acdx1",
+           "--format=u2c",
+           "--format",
+           "f",
+           "-xAx",
+           "--",
+           "-h",
+           "--format=f8")).unwrap(),
+       vec!(
+           FORMAT_ITEM_DEC64S,  // I
+           FORMAT_ITEM_DEC8U,   // tu1z
+           FORMAT_ITEM_HEX16,   // x
+           FORMAT_ITEM_A,       // ta
+           FORMAT_ITEM_C,       // tc
+           FORMAT_ITEM_DEC32S,  // td
+           FORMAT_ITEM_HEX8,    // tx1
+           FORMAT_ITEM_DEC16U,  // tu2
+           FORMAT_ITEM_C,       // tc
+           FORMAT_ITEM_F32,     // tf
+           FORMAT_ITEM_HEX16,   // x
+       ));
+}
diff --git a/src/od/prn_int.rs b/src/od/prn_int.rs
index 7f2b1b58f..da3fb1fb3 100644
--- a/src/od/prn_int.rs
+++ b/src/od/prn_int.rs
@@ -18,14 +18,12 @@ pub static FORMAT_ITEM_OCT32: FormatterItemInfo = FormatterItemInfo {
     formatter: FormatWriter::IntWriter(format_item_oct),
 };
 
-#[allow(dead_code)]
 pub static FORMAT_ITEM_OCT64: FormatterItemInfo = FormatterItemInfo {
     byte_size: 8,
-    print_width: 23, // max: 2000000000000000000000
+    print_width: 23, // max: 1777777777777777777777
     formatter: FormatWriter::IntWriter(format_item_oct),
 };
 
-#[allow(dead_code)]
 pub static FORMAT_ITEM_HEX8: FormatterItemInfo = FormatterItemInfo {
     byte_size: 1,
     print_width: 3, // max: ff
@@ -44,7 +42,6 @@ pub static FORMAT_ITEM_HEX32: FormatterItemInfo = FormatterItemInfo {
     formatter: FormatWriter::IntWriter(format_item_hex),
 };
 
-#[allow(dead_code)]
 pub static FORMAT_ITEM_HEX64: FormatterItemInfo = FormatterItemInfo {
     byte_size: 8,
     print_width: 17, // max: ffffffffffffffff
@@ -52,7 +49,6 @@ pub static FORMAT_ITEM_HEX64: FormatterItemInfo = FormatterItemInfo {
 };
 
 
-#[allow(dead_code)]
 pub static FORMAT_ITEM_DEC8U: FormatterItemInfo = FormatterItemInfo {
     byte_size: 1,
     print_width: 4, // max: 255
@@ -71,7 +67,6 @@ pub static FORMAT_ITEM_DEC32U: FormatterItemInfo = FormatterItemInfo {
     formatter: FormatWriter::IntWriter(format_item_dec_u),
 };
 
-#[allow(dead_code)]
 pub static FORMAT_ITEM_DEC64U: FormatterItemInfo = FormatterItemInfo {
     byte_size: 8,
     print_width: 21, // max:  18446744073709551615
@@ -79,7 +74,6 @@ pub static FORMAT_ITEM_DEC64U: FormatterItemInfo = FormatterItemInfo {
 };
 
 
-#[allow(dead_code)]
 pub static FORMAT_ITEM_DEC8S: FormatterItemInfo = FormatterItemInfo {
     byte_size: 1,
     print_width: 5, // max: -128
@@ -92,14 +86,12 @@ pub static FORMAT_ITEM_DEC16S: FormatterItemInfo = FormatterItemInfo {
     formatter: FormatWriter::IntWriter(format_item_dec_s),
 };
 
-#[allow(dead_code)]
 pub static FORMAT_ITEM_DEC32S: FormatterItemInfo = FormatterItemInfo {
     byte_size: 4,
     print_width: 12, // max: -2147483648
     formatter: FormatWriter::IntWriter(format_item_dec_s),
 };
 
-#[allow(dead_code)]
 pub static FORMAT_ITEM_DEC64S: FormatterItemInfo = FormatterItemInfo {
     byte_size: 8,
     print_width: 21, // max: -9223372036854775808
diff --git a/tests/test_od.rs b/tests/test_od.rs
index 5a7bd0699..d78dd316c 100644
--- a/tests/test_od.rs
+++ b/tests/test_od.rs
@@ -414,15 +414,18 @@ fn test_maxuint(){
 
     let input = [0xFFu8 ; 8];
     let expected_output = unindent("
-            0000000     37777777777     37777777777
+            0000000          1777777777777777777777
+                        37777777777     37777777777
                      177777  177777  177777  177777
                     377 377 377 377 377 377 377 377
+                               18446744073709551615
                          4294967295      4294967295
                       65535   65535   65535   65535
+                    255 255 255 255 255 255 255 255
             0000010
             ");
 
-    let result = new_ucmd!().arg("-O").arg("-o").arg("-b").arg("-D").arg("-d").run_piped_stdin(&input[..]);
+    let result = new_ucmd!().arg("--format=o8").arg("-Oobtu8").arg("-Dd").arg("--format=u1").run_piped_stdin(&input[..]);
 
     assert_empty_stderr!(result);
     assert!(result.success);