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404 lines
15 KiB
Markdown
404 lines
15 KiB
Markdown
# Terminal codes (ANSI/VT100) introduction
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Terminal (control) codes are used to issue specific commands to your
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terminal. This can be related to switching colors or positioning the
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cursor, i.e. anything that can't be done by the application itself.
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## How it technically works
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A terminal control code is a special sequence of characters that is
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printed (like any other text). If the terminal understands the code, it
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won't display the character-sequence, but will perform some action. You
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can print the codes with a simple `echo` command.
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<u>**Note:**</u> I see codes referenced as "Bash colors" sometimes
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(several "Bash tutorials" etc...): That's a completely incorrect
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definition.
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## The tput command
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Because there's a large number of different terminal control languages,
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usually a system has an intermediate communication layer. The real codes
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are looked up in a database **for the currently detected terminal type**
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and you give standardized requests to an API or (from the shell) to a
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command.
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One of these commands is `tput`. Tput accepts a set of acronyms called
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*capability names* and any parameters, if appropriate, then looks up the
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correct escape sequences for the detected terminal in the `terminfo`
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database and prints the correct codes (the terminal hopefully
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understands).
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## The codes
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In this list I'll focus on ANSI/VT100 control codes for the most common
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actions - take it as quick reference. The documentation of your terminal
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or the `terminfo` database is always the preferred source when something
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is unclear! Also the `tput` acronyms are usually the ones dedicated for
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ANSI escapes!
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I listed only the most relevant codes, of course, any ANSI terminal
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understands many more! But let's keep the discussion centered on common
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shell scripting ;-)
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If I couldn't find a matching ANSI escape, you'll see a :?: as the code.
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Feel free to mail me or fix it.
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The ANSI codes always start with the ESC character. (ASCII 0x1B or octal
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033) This isn't part of the list, but **you should avoid using the ANSI
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codes directly - use the `tput` command!**
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All codes that can be used with `tput` can be found in terminfo(5). (on
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OpenBSD at least) See [OpenBSD's
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terminfo(5)](http://www.openbsd.org/cgi-bin/man.cgi?query=terminfo&apropos=0&sektion=5&manpath=OpenBSD+Current&arch=i386&format=html)
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under the <u>Capabilities</u> section. The *cap-name* is the code to use
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with tput. A description of each code is also provided.
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### General useful ASCII codes
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The **Ctrl-Key** representation is simply associating the non-printable
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characters from ASCII code 1 with the printable (letter) characters from
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ASCII code 65 ("A"). ASCII code 1 would be `^A` (Ctrl-A), while ASCII
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code 7 (BEL) would be `^G` (Ctrl-G). This is a common representation
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(and input method) and historically comes from one of the VT series of
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terminals.
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| Name | decimal | octal | hex | C-escape | Ctrl-Key | Description |
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|-------|---------|-------|------|----------|----------|--------------------------------|
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| `BEL` | 7 | 007 | 0x07 | `\a` | `^G` | Terminal bell |
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| `BS` | 8 | 010 | 0x08 | `\b` | `^H` | Backspace |
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| `HT` | 9 | 011 | 0x09 | `\t` | `^I` | Horizontal TAB |
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| `LF` | 10 | 012 | 0x0A | `\n` | `^J` | Linefeed (newline) |
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| `VT` | 11 | 013 | 0x0B | `\v` | `^K` | Vertical TAB |
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| `FF` | 12 | 014 | 0x0C | `\f` | `^L` | Formfeed (also: New page `NP`) |
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| `CR` | 13 | 015 | 0x0D | `\r` | `^M` | Carriage return |
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| `ESC` | 27 | 033 | 0x1B | `<none>` | `^[` | Escape character |
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| `DEL` | 127 | 177 | 0x7F | `<none>` | `<none>` | Delete character |
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### Cursor handling
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<table>
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<thead>
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<tr class="header">
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<th>ANSI</th>
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<th>terminfo equivalent</th>
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<th>Description</th>
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</tr>
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</thead>
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<tbody>
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<tr class="odd">
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<td><code>[ <X> ; <Y> H</code><br />
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<code>[ <X> ; <Y> f</code></td>
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<td><code>cup <X> <Y></code></td>
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<td>Home-positioning to <code>X</code> and <code>Y</code>
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coordinates<br />
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:!: it seems that ANSI uses 1-1 as home while <code>tput</code> uses
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0-0</td>
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</tr>
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<tr class="even">
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<td><code>[ H</code></td>
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<td><code>home</code></td>
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<td>Move cursor to home position (0-0)</td>
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</tr>
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<tr class="odd">
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<td><code>7</code></td>
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<td><code>sc</code></td>
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<td>Save current cursor position</td>
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</tr>
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<tr class="even">
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<td><code>8</code></td>
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<td><code>rc</code></td>
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<td>Restore saved cursor position</td>
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</tr>
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<tr class="odd">
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<td>:?: most likely a normal code like <code>\b</code></td>
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<td><code>cub1</code></td>
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<td>move left one space (backspace)</td>
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</tr>
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<tr class="even">
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<td>VT100 <code>[ ? 25 l</code></td>
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<td><code>civis</code></td>
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<td>make cursor invisible</td>
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</tr>
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<tr class="odd">
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<td>VT100 <code>[ ? 25 h</code></td>
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<td><code>cvvis</code></td>
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<td>make cursor visible</td>
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</tr>
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</tbody>
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</table>
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### Erasing text
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<table>
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<thead>
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<tr class="header">
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<th style="text-align: left;">ANSI</th>
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<th style="text-align: left;">terminfo equivalent</th>
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<th style="text-align: left;">Description</th>
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</tr>
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</thead>
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<tbody>
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<tr class="odd">
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<td style="text-align: left;"><code>[ K</code><br />
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<code>[ 0 K</code></td>
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<td style="text-align: left;"><code>el</code></td>
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<td style="text-align: left;"><strong>Clear line</strong> from current
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cursor position <strong>to end</strong> of line</td>
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</tr>
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<tr class="even">
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<td style="text-align: left;"><code>[ 1 K</code></td>
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<td style="text-align: left;"><code>el1</code></td>
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<td style="text-align: left;"><strong>Clear line from beginning</strong>
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to current cursor position</td>
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</tr>
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<tr class="odd">
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<td style="text-align: left;"><code>[ 2 K</code></td>
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<td style="text-align: left;"><code>el2</code>:?:</td>
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<td style="text-align: left;"><strong>Clear whole line</strong> (cursor
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position unchanged)</td>
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</tr>
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</tbody>
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</table>
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### General text attributes
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| ANSI | terminfo equivalent | Description |
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|---------|-----------------------------|----------------------------------------------|
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| `[ 0 m` | `sgr0` | Reset all attributes |
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| `[ 1 m` | `bold` | Set "bright" attribute |
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| `[ 2 m` | `dim` | Set "dim" attribute |
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| `[ 3 m` | `smso` | Set "standout" attribute |
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| `[ 4 m` | set `smul` unset `rmul` :?: | Set "underscore" (underlined text) attribute |
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| `[ 5 m` | `blink` | Set "blink" attribute |
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| `[ 7 m` | `rev` | Set "reverse" attribute |
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| `[ 8 m` | `invis` | Set "hidden" attribute |
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### Foreground coloring
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| ANSI | terminfo equivalent | Description |
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|:----------|:--------------------|:----------------------------------------------|
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| `[ 3 0 m` | `setaf 0` | Set **foreground** to color \#0 - **black** |
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| `[ 3 1 m` | `setaf 1` | Set **foreground** to color \#1 - **red** |
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| `[ 3 2 m` | `setaf 2` | Set **foreground** to color \#2 - **green** |
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| `[ 3 3 m` | `setaf 3` | Set **foreground** to color \#3 - **yellow** |
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| `[ 3 4 m` | `setaf 4` | Set **foreground** to color \#4 - **blue** |
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| `[ 3 5 m` | `setaf 5` | Set **foreground** to color \#5 - **magenta** |
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| `[ 3 6 m` | `setaf 6` | Set **foreground** to color \#6 - **cyan** |
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| `[ 3 7 m` | `setaf 7` | Set **foreground** to color \#7 - **white** |
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| `[ 3 9 m` | `setaf 9` | Set **default** color as foreground color |
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### Background coloring
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| ANSI | terminfo equivalent | Description |
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|:----------|:--------------------|:----------------------------------------------|
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| `[ 4 0 m` | `setab 0` | Set **background** to color \#0 - **black** |
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| `[ 4 1 m` | `setab 1` | Set **background** to color \#1 - **red** |
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| `[ 4 2 m` | `setab 2` | Set **background** to color \#2 - **green** |
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| `[ 4 3 m` | `setab 3` | Set **background** to color \#3 - **yellow** |
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| `[ 4 4 m` | `setab 4` | Set **background** to color \#4 - **blue** |
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| `[ 4 5 m` | `setab 5` | Set **background** to color \#5 - **magenta** |
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| `[ 4 6 m` | `setab 6` | Set **background** to color \#6 - **cyan** |
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| `[ 4 7 m` | `setab 7` | Set **background** to color \#7 - **white** |
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| `[ 4 9 m` | `setab 9` | Set **default** color as background color |
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### Misc codes
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#### Save/restore screen
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Used capabilities: `smcup`, `rmcup`
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You've undoubtedly already encountered programs that restore the
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terminal contents after they do their work (like `vim`). This can be
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done by the following commands:
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# save, clear screen
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tput smcup
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clear
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# example "application" follows...
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read -n1 -p "Press any key to continue..."
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# example "application" ends here
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# restore
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tput rmcup
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These features require that certain capabilities exist in your
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termcap/terminfo. While `xterm` and most of its clones (`rxvt`, `urxvt`,
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etc) will support the instructions, your operating system may not
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include references to them in its default xterm profile. (FreeBSD, in
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particular, falls into this category.) If \`tput smcup\` appears to do
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nothing for you, and you don't want to modify your system
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termcap/terminfo data, and you KNOW that you are using a compatible
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xterm application, the following may work for you:
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echo -e '\033[?47h' # save screen
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echo -e '\033[?47l' # restore screen
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Certain software uses these codes (via their termcap capabilities) as
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well. You may have seen the screen save/restore in `less`, `vim`, `top`,
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`screen` and others. Some of these applications may also provide
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configuration options to \*disable\* this behaviour. For example, `less`
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has a `-X` option for this, which can also be set in an environment
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variable:
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export LESS=X
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less /path/to/file
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Similarly, `vim` can be configured not to "restore" the screen by adding
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the following to your `~/.vimrc`:
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set t_ti= t_te=
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#### Additional colors
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Some terminal emulators support additional colors. The most common
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extension used by xterm-compatible terminals supports 256 colors. These
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can be generated by `tput` with `seta{f,b} [0-255]` when the `TERM`
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value has a `-256color` suffix. [Some
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terminals](https://gist.github.com/XVilka/8346728#now-supporting-truecolour)
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also support full 24-bit colors, and any X11 color code can be written
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directly into a special escape sequence. ([More
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infos](https://gist.github.com/XVilka/8346728)) Only a few programs make
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use of anything beyond 256 colors, and tput doesn't know about them.
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Colors beyond 16 usually only apply to modern terminal emulators running
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in graphical environments.
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The Virtual Terminal implemented in the Linux kernel supports only 16
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colors, and the usual default terminfo entry for `TERM=linux` defines
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only 8. There is sometimes an alternate "linux-16color" that you can
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switch to, to get the other 8 colors.
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## Bash examples
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### Hardcoded colors
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printf '%b\n' 'It is \033[31mnot\033[39m intelligent to use \033[32mhardcoded ANSI\033[39m codes!'
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### Colors using tput
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<u>Directly inside the echo:</u>
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echo "TPUT is a $(tput setaf 2)nice$(tput setaf 9) and $(tput setaf 5)user friendly$(tput setaf 9) terminal capability database."
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<u>With preset variables:</u>
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COL_NORM="$(tput setaf 9)"
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COL_RED="$(tput setaf 1)"
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COL_GREEN="$(tput setaf 2)"
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echo "It's ${COL_RED}red${COL_NORM} and ${COL_GREEN}green${COL_NORM} - have you seen?"
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### Misc
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<u>HOME function</u>
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home() {
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# yes, actually not much shorter ;-)
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tput home
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}
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### Silly but nice effect
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#!/bin/bash
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DATA[0]=" _/ _/ _/ _/ "
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DATA[1]=" _/_/_/_/_/ _/_/_/ _/_/_/ _/_/_/ _/_/_/ "
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DATA[2]=" _/ _/ _/ _/ _/ _/ _/_/ _/ _/"
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DATA[3]="_/_/_/_/_/ _/ _/ _/ _/ _/_/ _/ _/ "
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DATA[4]=" _/ _/ _/_/_/ _/_/_/ _/_/_/ _/ _/ "
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# virtual coordinate system is X*Y ${#DATA} * 5
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REAL_OFFSET_X=0
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REAL_OFFSET_Y=0
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draw_char() {
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V_COORD_X=$1
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V_COORD_Y=$2
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tput cup $((REAL_OFFSET_Y + V_COORD_Y)) $((REAL_OFFSET_X + V_COORD_X))
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printf %c ${DATA[V_COORD_Y]:V_COORD_X:1}
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}
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trap 'exit 1' INT TERM
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trap 'tput setaf 9; tput cvvis; clear' EXIT
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tput civis
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clear
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while :; do
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for ((c=1; c <= 7; c++)); do
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tput setaf $c
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for ((x=0; x<${#DATA[0]}; x++)); do
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for ((y=0; y<=4; y++)); do
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draw_char $x $y
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done
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done
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done
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done
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### Mandelbrot set
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This is a slightly modified version of Charles Cooke's colorful
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Mandelbrot plot scripts ([original w/
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screenshot](http://earth.gkhs.net/ccooke/shell.html)) -- ungolfed,
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optimized a bit, and without hard-coded terminal escapes. The `colorBox`
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function is [memoized](http://en.wikipedia.org/wiki/Memoization) to
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collect `tput` output only when required and output a new escape only
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when a color change is needed. This limits the number of `tput` calls to
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at most 16, and reduces raw output by more than half. The `doBash`
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function uses integer arithmetic, but is still ksh93-compatible (run as
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e.g. `bash ./mandelbrot` to use it). The ksh93-only floating-point
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`doKsh` is almost 10x faster than `doBash` (thus the ksh shebang by
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default), but uses only features that don't make the Bash parser crash.
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#!/usr/bin/env ksh
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# Charles Cooke's 16-color Mandelbrot
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# http://earth.gkhs.net/ccooke/shell.html
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# Combined Bash/ksh93 flavors by Dan Douglas (ormaaj)
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function doBash {
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typeset P Q X Y a b c i v x y
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for ((P=10**8,Q=P/100,X=320*Q/cols,Y=210*Q/lines,y=-105*Q,v=-220*Q,x=v;y<105*Q;x=v,y+=Y)); do
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for ((;x<P;a=b=i=c=0,x+=X)); do
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for ((;a**2+b**2<4*P**2&&i++<99;a=((c=a)**2-b**2)/P+x,b=2*c*b/P+y)); do :
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done
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colorBox $((i<99?i%16:0))
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done
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echo
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done
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}
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function doKsh {
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integer i
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float a b c x=2.2 y=-1.05 X=3.2/cols Y=2.1/lines
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while
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for ((a=b=i=0;(c=a)**2+b**2<=2&&i++<99&&(a=a**2-b**2+x,b=2*c*b+y);)); do :
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done
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. colorBox $((i<99?i%16:0))
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if ((x<1?!(x+=X):(y+=Y,x=-2.2))); then
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print
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((y<1.05))
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fi
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do :
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done
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}
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function colorBox {
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(($1==lastclr)) || printf %s "${colrs[lastclr=$1]:=$(tput setaf "$1")}"
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printf '\u2588'
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}
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unset -v lastclr
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((cols=$(tput cols)-1, lines=$(tput lines)))
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typeset -a colrs
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trap 'tput sgr0; echo' EXIT
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${KSH_VERSION+. doKsh} ${BASH_VERSION+doBash}
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