bash PROMPT_COMMAND syntax error

[FernandoBasso]

Intro

It seems the the Kitty bash shell integration script is inserting a semicolon on the PROMPT_COMMAND causing it to conflict with what another program is doing with PROMPT_COMMAND. It this case it is with the z program.

Both kitty and z have been installed from the Arch Linux official repositories.

To Reproduce
Steps to reproduce the behavior:

1. In ~/bashrc, source /usr/share/z/z.sh (this could change depending on the distro or if installed manually in ~/bin or something like it);
2. Open a fresh kitty instance (it adds some lines to ~/.bashrc:

# BEGIN_KITTY_SHELL_INTEGRATION
if test -n "$KITTY_INSTALLATION_DIR" -a -e "$KITTY_INSTALLATION_DIR/shell-integration/bash/kitty.bash"; then source "$KITTY_INSTALLATION_DIR/shell-integration/bash/kitty.bash"; fi
# END_KITTY_SHELL_INTEGRATION

3. See the following bash syntax error message:

bash: PROMPT_COMMAND: line 1: syntax error near unexpected token `;;'
bash: PROMPT_COMMAND: line 1: `(_z --add "$(command pwd -P 2>/dev/null)" 2>/dev/null &);; _ksi_prompt_command'

Note the two semicolons.

Environment details

kitty 0.24.2 created by Kovid Goyal
Linux theforce 5.16.5-arch1-1 #1 SMP PREEMPT Tue, 01 Feb 2022 21:42:50 +0000 x86_64
Arch Linux 5.16.5-arch1-1 (/dev/tty)

LSB_VERSION=1.4
DISTRIB_ID=Arch
DISTRIB_RELEASE=rolling
DISTRIB_DESCRIPTION="Arch Linux"
Running under: X11
Frozen: False
Paths:
  kitty: /usr/bin/kitty
  base dir: /usr/lib/kitty
  extensions dir: /usr/lib/kitty/kitty
  system shell: /bin/bash
Loaded config files:
  /home/fernando/.config/kitty/kitty.conf

I redacted the debug part that seemed to be irrelevant for this topic. The config seems not useful here either. I can provide both if requested.

Additional context

$ declare -p PROMPT_COMMAND 
declare -- PROMPT_COMMAND="printf \"\\033]0;%s@%s:%s\\007\" \"\${USER}\" \"\${HOSTNAME%%.*}\" \"\${PWD/#\$HOME/\\~}\"
(_z --add \"\$(command pwd -P 2>/dev/null)\" 2>/dev/null &);; _ksi_prompt_command"

As we see, there are two semicolons (;;) before _ksi_prompt_command.

Here's an excerpt from /usr/lib/kitty/shell-integration/bash/kitty.bash:

If I remove the semicolon highlighted in the screenshot, or if I refrain from sourcing z.sh, the problem disappears.

I have been using z for about 5 years and Kitty for about two years. Both have always worked fine and not interfering with one another. Also, z has not had an upgrade for years. I guess a recent Kitty upgrade added that part of the bash script and the problem came into existence.

Here's an excerpt of /usr/share/z/z.sh bash script:

So, z bash script adds a trailing semicolon, while Kitty bash script prepends a semicolon (perhaps defensively in the else case). Note that if I remove that trailing semicolon from z.sh, it simply stops working. That is, if I do z dotfiles, it simply does nothing (it does not change directory to my dotfiles directory). So, it seems it is not a matter of simply removing that semicolon from z.sh.

If I remove the leading semicolon before _ksi_prompt_command, I get no errors, but z doesn't work either. I get no syntax errors, but it seems PROMPT_COMMAND is somehow messed up nonetheless.

I'm not sure if there is a wrong one here. Perhaps it is just a case of bad luck — an unforeseeable situation — or if one of the programs should really change their addition of that specific semicolon something else.

I can create the same syntax error with this:

$ unset PROMPT_COMMAND 

$ (echo hello &); printf 'world'
hello
world

$ (echo hello &);; printf 'world'
bash: syntax error near unexpected token `;;'

[page-down]

I've noticed this before and I thought it had no effect.
I'm curious how to better join the commands in bash.

[securerootd]

@kovidgoyal I am using 0.24.2 and with hstr I am getting the same error:

$ -> hstr --show-configuration


# HSTR configuration - add this to ~/.bashrc
alias hh=hstr                    # hh to be alias for hstr
export HSTR_CONFIG=hicolor       # get more colors
shopt -s histappend              # append new history items to .bash_history
export HISTCONTROL=ignorespace   # leading space hides commands from history
export HISTFILESIZE=10000        # increase history file size (default is 500)
export HISTSIZE=${HISTFILESIZE}  # increase history size (default is 500)
# ensure synchronization between bash memory and history file
export PROMPT_COMMAND="history -a; history -n; ${PROMPT_COMMAND}"
# if this is interactive shell, then bind hstr to Ctrl-r (for Vi mode check doc)
if [[ $- =~ .*i.* ]]; then bind '"\C-r": "\C-a hstr -- \C-j"'; fi
# if this is interactive shell, then bind 'kill last command' to Ctrl-x k
if [[ $- =~ .*i.* ]]; then bind '"\C-xk": "\C-a hstr -k \C-j"'; fi

bash: PROMPT_COMMAND: line 7: syntax error near unexpected token `;'
bash: PROMPT_COMMAND: line 7: `history -a; history -n; history -a; history -n; ; _ksi_prompt_command'

$ -> kitty -v
kitty 0.24.2 created by Kovid Goyal
bash: PROMPT_COMMAND: line 9: syntax error near unexpected token `;'
bash: PROMPT_COMMAND: line 9: `history -a; history -n; history -a; history -n; ; _ksi_prompt_command'

$ -> declare -p PROMPT_COMMAND 
declare -x PROMPT_COMMAND="history -a; history -n; history -a; history -n; ; _ksi_prompt_command"
bash: PROMPT_COMMAND: line 10: syntax error near unexpected token `;'
bash: PROMPT_COMMAND: line 10: `history -a; history -n; history -a; history -n; ; _ksi_prompt_command'

[kovidgoyal]

and? The fix will be in 0.24.3

[securerootd]

and? The fix will be in 0.24.3

Ah - I misunderstood. I thought the fix was already in 0.24.2 - thanks for clarifying.

[smichel17]

kitty 0.24.4, bash 5.1 (from homebrew)

$ kitty -v
kitty 0.24.4 created by Kovid Goyal

$ bash --version
GNU bash, version 5.1.16(1)-release (x86_64-apple-darwin21.1.0)
Copyright (C) 2020 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Unfortunately I've run into a nearly identical bug, when using powerline.

-bash: PROMPT_COMMAND: line 1: syntax error near unexpected token `;'
-bash: PROMPT_COMMAND: line 1: `; builtin declare -F _ksi_prompt_command > /dev/null 2> /dev/null && _ksi_prompt_command'

$ declare -p PROMPT_COMMAND
declare -- PROMPT_COMMAND="_powerline_status_wrapper _powerline_set_prompt
; builtin declare -F _ksi_prompt_command > /dev/null 2> /dev/null && _ksi_prompt_command"

Fortunately, I found a workaround:

• In kitty.conf, set shell_integration no-rc.
• In .bashrc, manually init kitty shell integration before powerline setup:

# BEGIN_KITTY_SHELL_INTEGRATION
# This part was not present when reproducing the bug
if test -n "$KITTY_INSTALLATION_DIR" -a -e "$KITTY_INSTALLATION_DIR/shell-integration/bash/kitty.bash"; then
    source "$KITTY_INSTALLATION_DIR/shell-integration/bash/kitty.bash"
fi
# END_KITTY_SHELL_INTEGRATION

# Enable Powerline
# This was also present to produce the bug
if [ -f "$(command -v powerline-daemon)" ]; then
  powerline-daemon -q
  POWERLINE_BASH_CONTINUATION=1
  POWERLINE_BASH_SELECT=1
  # This is terrible. There must be a better way than hard-coding this path.
  . /usr/local/lib/python3.9/site-packages/powerline/bindings/bash/powerline.sh
fi

This produces

$ declare -p PROMPT_COMMAND
declare -a PROMPT_COMMAND=([0]=$'_powerline_status_wrapper _powerline_set_prompt\nbuiltin declare -F _ksi_prompt_command > /dev/null 2> /dev/null && _ksi_prompt_command')

I'm not sure if this is a bug in kitty or powerline, but I'm posting here since I found it as a related issue in my searching; let me know if I should report it to powerline, too (or in its own issue here).

[page-down]

Minimal reproducer

# This works fine
PROMPT_COMMAND=":; "
# Error when more than one space.
PROMPT_COMMAND=":;  "
# or when using newline
PROMPT_COMMAND=":"$'\n' 

# syntax error near unexpected token `;'

Patch

# kitty.bash

# Remove all trailing whitespace chars
PROMPT_COMMAND="${PROMPT_COMMAND%"${PROMPT_COMMAND##*[![:space:]]}"}"
PROMPT_COMMAND="${PROMPT_COMMAND%%;}"

# Or use a newline
PROMPT_COMMAND+=$'\n'"$pc"

[kovidgoyal]

5641668

[page-down]

5641668

Does not work when there is more than one whitespace character, is it worth removing?

[kovidgoyal]

I have used exglob to handle multiple chars.

[smichel17]

Thank you both for the better reproduction and exceptionally quick fix :)