LinuxQuestions.org - Appending to PROMPT

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- - Appending to PROMPT_COMMAND (https://www.linuxquestions.org/questions/linux-newbie-8/appending-to-prompt_command-835322/)

Appending to PROMPT_COMMAND

I have the following as my $PROMPT_COMMAND in .bashrc:

Code:

PROMPT_COMMAND='

if [ $TERM = "screen" ]; then

 MYPWD="${PWD/#$HOME/~}"

 [ ${#MYPWD} -gt 20 ] && MYPWD=..${MYPWD:${#MYPWD}-18}

 echo -n -e "\033k$MYPWD\033\\"

fi

'

I am trying to append items to my PROMPT_COMMAND in another script/on command line. If I do the following:

Code:

export PROMPT_COMMAND="$PROMPT_COMMAND && ls"

bash has a syntax error and complains of unexpected token near &&.
But if I change the following in .bashrc

Code:

PROMPT_COMMAND='

if [ $TERM = "screen" ]; then

 MYPWD="${PWD/#$HOME/~}"

 [ ${#MYPWD} -gt 20 ] && MYPWD=..${MYPWD:${#MYPWD}-18}

 echo -n -e "\033k$MYPWD\033\\"

fi && ls

'

I get no error.

I've echoed the value of $PROMPT_COMMAND in both cases and their output is exactly the same.

Any tips? Thanks.

It probably has to do with the fact that you already have quotes inside the original prompt command.

I am curious what you expect to happen?

If you did the following on the command line:

Code:

PROMPT_COMMAND="$PROMPT_COMMAND && ls"

And now perform an echo, all that has happened is '&& ls' gets appended to the string.

The questions then becomes, what is processing $PROMPT_COMMAND?

Quote:

Originally Posted by grail (Post 4113309)

I am curious what you expect to happen?

If you did the following on the command line:

Code:

PROMPT_COMMAND="$PROMPT_COMMAND && ls"

And now perform an echo, all that has happened is '&& ls' gets appended to the string.

The questions then becomes, what is processing $PROMPT_COMMAND?

bash is processing $PROMPT_COMMAND
http://tldp.org/HOWTO/Bash-Prompt-HOWTO/x264.html

I've solved it, I had to put the last quote on the same line as the last fi

Code:

PROMPT_COMMAND='

if [ $TERM = "screen" ]; then

 MYPWD="${PWD/#$HOME/~}"

 [ ${#MYPWD} -gt 20 ] && MYPWD=..${MYPWD:${#MYPWD}-18}

 echo -n -e "\033k$MYPWD\033\\"

fi'

Now if someone can tell me why the previous version didn't work..

Code:

PROMPT_COMMAND='

if [ $TERM = "screen" ]; then

 MYPWD="${PWD/#$HOME/~}"

 [ ${#MYPWD} -gt 20 ] && MYPWD=..${MYPWD:${#MYPWD}-18}

 echo -n -e "\033k$MYPWD\033\\"

fi

'

Edit: Maybe because && can't start on a newline?

Because the fi command needs to be terminated -- by a ; or by a newline.