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Old 11-16-2011, 08:13 PM
Mantas MikulÄ—nas
Default Dynamic Titles in urxvt (bash) Without Side Effects?

On 2011-11-16 15:51, Bastien Dejean wrote:


I've added the following lines to my .bashrc:

case "$TERM" in
set -o functrace
trap '[ -z "$BASH_SOURCE" ]&& printf "%b" "e]0;$BASH_COMMANDa"' DEBUG>& /dev/null

(It sets the current title of the current window according to the last
ran command.)

But alas, it generates side effects, if I issue this:

ls "$(ls -1 | head -1)"

I get:

ls: cannot access foo.bar: No such file or directory

Strange or trivial?

First, you are using `printf` the wrong way. Such sequences as e]0; are
supposed to be in the first argument, just like C printf():

printf "e]0;%sa" "$BASH_COMMAND"

Your current method causes backslash escapes to be expanded not only in
the literal e and a, but also in the value of $BASH_COMMAND; so, for
example, if you ran this interactively:

echo "a is a bell"

then your current `printf` command would receive:

e]0;echo "a is a bell"a

which causes the title to be set to 'echo "', and the remainder text to
be displayed normally (' is a bell"a').

Second, your `ls` failure is caused by your `printf` output. It seems
that the DEBUG trap handler is executed for subshells as well, with the
trap handler's stdout being captured along with the actual command's
stdout. In this case, $() will return your title-setting sequence. For

echo "$(true)" > testfile

Normally, 'testfile' would be blank, but in this case...

You can sort of avoid this by redirecting the output to the proper
location -- your terminal. (I'm not sure how reliable this is.)

trap '[[ $BASH_SOURCE ]] ||
printf "e]0;%sa" "$BASH_COMMAND" >/dev/tty' DEBUG

Mantas M.

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