Terminal escape sequences

Ruby
1

Hi all,

Looking through the PDoc source to see how it renders the build progress
meter, I see:

log “\c[[F\c[[K Rendering: #{dest}”

Is there a good reference for these escape sequences anywhere? They’re
not
terribly Google-friendly.

2

Hi,

2009/8/6 James C. [email protected]:

Hi all,

Looking through the PDoc source to see how it renders the build progress
meter, I see:

 log “\c[[F\c[[K   Rendering: #{dest}”

Is there a good reference for these escape sequences anywhere? They’re not
terribly Google-friendly.

“\c[” is same to “\e”
“\c[[F” is invalid sequence. cf: “\c[[f” means “Move cursor to upper
left corner”
“\c[[K” means “Clear line from cursor right”

Refer to http://ascii-table.com/ansi-escape-sequences-vt-100.php

Regards,

Park H.

3

2009/8/6 Heesob P. [email protected]

Is there a good reference for these escape sequences anywhere? They’re
not
terribly Google-friendly.

“\c[” is same to “\e”
“\c[[F” is invalid sequence. cf: “\c[[f” means “Move cursor to upper
left corner”
“\c[[K” means “Clear line from cursor right”

Refer to http://ascii-table.com/ansi-escape-sequences-vt-100.php

Thanks. \e[F is not listed though on my system it seems to have the
effect
of returning the cursor to the start of the line, so \e[F\e[K can be
used to
overwrite the whole of the current line. Anyone know if this is commonly
implemented or is it Ubuntu-specific?

James

4

2009/8/6 Heesob P. [email protected]:

Is there a good reference for these escape sequences anywhere? They’re not
terribly Google-friendly.

“\c[” is same to “\e”
“\c[[F” is invalid sequence. cf: “\c[[f” means “Move cursor to upper
left corner”
“\c[[K” means “Clear line from cursor right”

Refer to http://ascii-table.com/ansi-escape-sequences-vt-100.php

Correction:
“\c[[F” means “Cursor Preceding Line”
“\c[[K” means “Erase in Line”

Refer to Miscellaneous Text Files: Ansi escape code sequences

Regards,

Park H.

5

James C. [email protected] writes:

terribly Google-friendly.
Each terminal kind has its own escape sequences. There are thousands
of different kinds of terminals. A subset of their escape sequences
are referenced in the termcap or terminfo files, for use by libraries
such as curses, to provide a certain level of terminal independance on
the application side.

However, nowadays we don’t use many physical terminals anymore. We
still use virtual terminals (xterm, Terminal.app, etc). So there is
still diversity, but much less.

There are standardized escape sequences, and most kinds of terminal
actually includes at least a basic subset of these standard escape
sequences. There’s the ISO-6429 standard, but you will need money to
get it. There is also the ECMA-048 standard which should be identical
to ISO-6429 and can be downloaded from the web. There’s also an ANSI
standard that should be identical or quite similar, but I don’t know
the reference. However, these standard escape sequences are often
known by the name ANSI escape sequences (probably because on Microsoft
systems they’re implemented by a module stored in a file named
ANSI.SYS).

So to have the highest possible level of terminal compatibility, you
should rather use a curses library (which will select the escape
sequence to send depending on the terminal of the user).

If you choose to use these standard escape sequences, you will
restrict your program to terminals that implement these standard
escape sequences (probably 95% of the (virtual) terminals in use
today, so not a big loss).

But even in this later case, I would advise you to abstract them away.

Instead of writting:

log "\c[[F\c[[K    Rendering: #{dest}"

write:

log "#{Ecma048.cpl}${Ecma048.el}   Rendering: #{dest}"

(Notice that most of these escape sequences may take optional numeric
arguments.
CPL (Cursor Preceding Line) with an argument would could back several
lines.)

6

Hi,

Am Donnerstag, 06. Aug 2009, 17:56:53 +0900 schrieb James C.:

Looking through the PDoc source to see how it renders the build progress
meter, I see:

log “\c[[F\c[[K Rendering: #{dest}”

Is there a good reference for these escape sequences anywhere? They’re not
terribly Google-friendly.

This is the whole truth: http://www.xfree86.org/current/ctlseqs.html.

Be aware that there are a lot of terminal programs (xterm, KDE,
Gnome, Xfce4, aterm, wterm, …) and not everything is implemented
everywhere.

If you like to track what escape sequences some programs write
you can use the script command.

Bertram

7

Heesob P. [email protected] writes:

Is there a good reference for these escape sequences anywhere? They’re not
terribly Google-friendly.

“\c[” is same to “\e”
“\c[[F” is invalid sequence. cf: “\c[[f” means “Move cursor to upper
left corner”

ESC [ F is CPL, Cursor Preceding Line, in ECMA-048.

“\c[[K” means “Clear line from cursor right”

Refer to http://ascii-table.com/ansi-escape-sequences-vt-100.php

Which would only prove that the VT-100 terminals don’t implement
ECMA-048.