意外标记“then”附近的语法错误

当我尝试在 Ubuntu 终端中更新（源 .bashrc）我的 .bashrc 以更改别名时，出现错误

bash: ./.bashrc: line 34: syntax error near unexpected token `then'
bash: ./.bashrc: line 34: `if [ -z "${debian_chroot:-}" ] && [ -r /etc/debian_chroot ]; then'

这是关于.bashrc中的这段代码：

# set variable identifying the chroot you work in (used in the prompt below)
if [ -z "${debian_chroot:-}" ] && [ -r /etc/debian_chroot ]; then
    debian_chroot=$(cat /etc/debian_chroot)
fi

在 .bashrc 的顶部添加 set -x，我得到以下关于输出的额外信息：

+ source .bashrc
++ case $- in
++ HISTCONTROL=ignoreboth
++ shopt -s histappend
++ HISTSIZE=1000
++ HISTFILESIZE=2000
++ shopt -s checkwinsize
++ '[' -x /usr/bin/lesspipe ']'
+++ SHELL=/bin/sh
+++ lesspipe
++ eval 'export LESSOPEN="| /usr/bin/lesspipe %s";
export LESSCLOSE="/usr/bin/lesspipe %s %s";'
+++ export 'LESSOPEN=| /usr/bin/lesspipe %s'
+++ LESSOPEN='| /usr/bin/lesspipe %s'
+++ export 'LESSCLOSE=/usr/bin/lesspipe %s %s'
+++ LESSCLOSE='/usr/bin/lesspipe %s %s'

我已通过 /etc/skel 将我的 .bashrc 恢复为默认值，但错误仍然出现，因为这部分代码似乎是默认值。下面是我完整的 .bashrc 文件。

# ~/.bashrc: executed by bash(1) for non-login shells.
# see /usr/share/doc/bash/examples/startup-files (in the package bash-doc)
# for examples

# If not running interactively, don't do anything
case $- in
    *i*) ;;
      *) return;;
esac

# don't put duplicate lines or lines starting with space in the history.
# See bash(1) for more options
HISTCONTROL=ignoreboth

# append to the history file, don't overwrite it
shopt -s histappend

# for setting history length see HISTSIZE and HISTFILESIZE in bash(1)
HISTSIZE=1000
HISTFILESIZE=2000

# check the window size after each command and, if necessary,
# update the values of LINES and COLUMNS.
shopt -s checkwinsize

# If set, the pattern "**" used in a pathname expansion context will
# match all files and zero or more directories and subdirectories.
#shopt -s globstar

# make less more friendly for non-text input files, see lesspipe(1)
[ -x /usr/bin/lesspipe ] && eval "$(SHELL=/bin/sh lesspipe)"

# set variable identifying the chroot you work in (used in the prompt below)
if [ -z "${debian_chroot:-}" ] && [ -r /etc/debian_chroot ]; then
    debian_chroot=$(cat /etc/debian_chroot)
fi

# set a fancy prompt (non-color, unless we know we "want" color)
case "$TERM" in
    xterm-color|*-256color) color_prompt=yes;;
esac

# uncomment for a colored prompt, if the terminal has the capability; turned
# off by default to not distract the user: the focus in a terminal window
# should be on the output of commands, not on the prompt
#force_color_prompt=yes

if [ -n "$force_color_prompt" ]; then
    if [ -x /usr/bin/tput ] && tput setaf 1 >&/dev/null; then
    # We have color support; assume it's compliant with Ecma-48
    # (ISO/IEC-6429). (Lack of such support is extremely rare, and such
    # a case would tend to support setf rather than setaf.)
    color_prompt=yes
    else
    color_prompt=
    fi
fi

if [ "$color_prompt" = yes ]; then
    PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
else
    PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
fi
unset color_prompt force_color_prompt

# If this is an xterm set the title to user@host:dir
case "$TERM" in
xterm*|rxvt*)
    PS1="\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a\]$PS1"
    ;;
*)
    ;;
esac

# enable color support of ls and also add handy aliases
if [ -x /usr/bin/dircolors ]; then
    test -r ~/.dircolors && eval "$(dircolors -b ~/.dircolors)" || eval "$(dircolors -b)"
    alias ls='ls --color=auto'
    #alias dir='dir --color=auto'
    #alias vdir='vdir --color=auto'

    alias grep='grep --color=auto'
    alias fgrep='fgrep --color=auto'
    alias egrep='egrep --color=auto'
fi

# colored GCC warnings and errors
#export GCC_COLORS='error=01;31:warning=01;35:note=01;36:caret=01;32:locus=01:quote=01'

# some more ls aliases
alias ll='ls -alF'
alias la='ls -A'
alias l='ls -CF'

# Add an "alert" alias for long running commands.  Use like so:
#   sleep 10; alert
alias alert='notify-send --urgency=low -i "$([ $? = 0 ] && echo terminal || echo error)" "$(history|tail -n1|sed -e '\''s/^\s*[0-9]\+\s*//;s/[;&|]\s*alert$//'\'')"'

# Alias definitions.
# You may want to put all your additions into a separate file like
# ~/.bash_aliases, instead of adding them here directly.
# See /usr/share/doc/bash-doc/examples in the bash-doc package.

if [ -f ~/.bash_aliases ]; then
    . ~/.bash_aliases
fi

# enable programmable completion features (you don't need to enable
# this, if it's already enabled in /etc/bash.bashrc and /etc/profile
# sources /etc/bash.bashrc).
if ! shopt -oq posix; then
  if [ -f /usr/share/bash-completion/bash_completion ]; then
    . /usr/share/bash-completion/bash_completion
  elif [ -f /etc/bash_completion ]; then
    . /etc/bash_completion
  fi
fi

export HOME_T_exp=/home/boris/Tetra
export HTB=$HOME_T_exp/bin
export P_plot=$HOME_T_exp/P_plot
export PATH=$PATH:.:$HOME_T_exp/bin:$P_plot/uscr

alias vb='vi .bashrc'
alias sb='source .bashrc'

alias ci='vi'

alias hom='cd /home/boris'
alias pic='cd ~/Pictures'
alias tet='cd ~/Tetra'
alias dat='cd ~/Tetra/Data'
alias mrg='cd ~/Tetra/Data/Merge_data'

alias rd='cd ~/Tetra/Run_Mediterranean'
alias rf='cd ~/Tetra/Run_Mediterranean/Run_faults'
alias rnf='cd ~/Tetra/Run_Mediterranean/Run_nofaults'
alias rf1='cd ~/Tetra/Run_Mediterranean/Run_onepar_faults'
alias rnf1='cd ~/Tetra/Run_Mediterranean/Run_onepar_nofaults'

alias if='cd ~/Tetra/Run_Mediterranean/Run_faults/I_0'
alias inf='cd ~/Tetra/Run_Mediterranean/Run_nofaults/I_0'
alias if1='cd ~/Tetra/Run_Mediterranean/Run_onepar_faults/I_0'
alias inf1='cd ~/Tetra/Run_Mediterranean/Run_onepar_nofaults/I_0'

alias sf='cd ~/Tetra/Run_Mediterranean/Run_faults/SYNTH'
alias snf='cd ~/Tetra/Run_Mediterranean/Run_nofaults/SYNTH'
alias sf1='cd ~/Tetra/Run_Mediterranean/Run_onepar_faults/SYNTH'
alias snf1='cd ~/Tetra/Run_Mediterranean/Run_onepar_nofaults/SYNTH'

alias src='cd ~/Tetra/Src'
alias bin='cd ~/Tetra/bin'
alias ppl='cd ~/Tetra/P_plot'

alias tsh='cd /media/boris/toshiba'
alias sdm='sudo mount /dev/sda1/media/boris/toshiba'
alias gf='gfortran'

export T=~/Tetra
export P=$T/P_plot

export IMagick=/home/boris
export MAGICK_HOME=$IMagick/ImageMagick-7.0.8-23
export DYLD_LIBRARY_PATH=$MAGICK_HOME/lib

export PATH=$MAGICK_HOME/utilities:$PATH

export LS_COLORS="$LS_COLORS:ow=1;34:tw=1;34:"

有谁知道这个问题的解决方案？