编写Shell脚本格式化LaTeX文件：为公式环境加空行与\noindent

需求与问题 #

需要编写Shell脚本实现LaTeX文件的两项格式化：

• 为所有equation和align环境前后各添加一个空行，且重复运行脚本时不会重复添加空行
• 在equation/align环境结束后的段落开头添加\noindent命令

现有脚本仅实现了部分空行添加功能，但存在重复添加空行的问题，且未完成\noindent的添加逻辑。

现有脚本 #

# Check if a filename is provided
if [ "$#" -ne 1 ]; then
    echo "Usage: $0 filename"
    exit 1
fi

# Check if the file exists
if [ ! -f $1 ]; then
    echo "File $1 not found!"
    exit 1
fi

# Process the file
awk '
BEGIN {
    RS = "\n"
    ORS = "\n"
    prev_line = ""
    prev_prev_line = ""
}
{
    if ($0 ~ /\\begin\{equation\}|\\begin\{align\}/) {
        if (prev_line !~ /^$/ && prev_prev_line !~ /\\begin\{equation\}|\\begin\{align\}/) {
            print "\n" $0
        } else {
            print $0
        }
    } else if ($0 ~ /\\end\{equation\}|\\end\{align\}/) {
        if (prev_line !~ /^$/ && prev_prev_line !~ /\\end\{equation\}|\\end\{align\}/) {
            print $0 "\n"
        } else {
            print $0
        }
    } else {
        print $0
    }
    prev_prev_line = prev_line
    prev_line = $0
}' $1 > $1.tmp

# Replace the original file with the processed file
mv $1.tmp $1

改进后的脚本 #

通过跟踪环境状态、检查空行存在性、处理\noindent插入逻辑，解决重复添加和命令插入问题：

#!/bin/bash

# 检查参数数量
if [ "$#" -ne 1 ]; then
    echo "Usage: $0 filename"
    exit 1
fi

# 检查文件存在
if [ ! -f "$1" ]; then
    echo "File $1 not found!"
    exit 1
fi

# 使用awk处理文件
awk '
BEGIN {
    in_env = 0          # 是否处于equation/align环境中
    after_env = 0       # 是否刚结束环境
    ORS = "\n"
}
# 匹配环境开始
/^\\begin\{(equation|align)\}/ {
    # 如果前一行不是空行，先打印空行
    if (prev_line !~ /^$/ && !in_env) {
        print ""
    }
    print $0
    in_env = 1
    after_env = 0
    prev_line = $0
    next
}
# 匹配环境结束
/^\\end\{(equation|align)\}/ {
    print $0
    in_env = 0
    after_env = 1
    prev_line = $0
    next
}
# 处理非环境行
{
    # 刚结束环境的情况：跳过空行，插入\noindent（如果不存在）
    if (after_env) {
        if ($0 ~ /^$/) {
            print $0
            prev_line = $0
            next
        }
        if ($0 !~ /^\\noindent/) {
            print ""
            print "\\noindent"
        }
        after_env = 0
    }
    # 处理环境开始后的空行（避免重复）
    if (!in_env && prev_line ~ /^\\begin\{(equation|align)\}/ && $0 !~ /^$/) {
        print ""
    }
    print $0
    prev_line = $0
}
' "$1" > "$1.tmp"

# 替换原文件
mv "$1.tmp" "$1"

效果验证 #

原LaTeX内容 #

To simplify the equation, we can assume that the perturbation of the Lagrangian displacement is proportional to a spherical harmonic function, $Y_{\ell m}(\theta,\phi)$, where $\ell$ is the degree of the harmonic and $m$ is the azimuthal order. Then, we can write:
\begin{equation}
\xi(r,\theta,\phi) = \sum_{\ell=0}^{\infty}\sum_{m=-\ell}^{\ell} \xi_{\ell m}(r) Y_{\ell m}(\theta,\phi)
\end{equation}
Substituting this expression into the equation of motion, we obtain:
\begin{equation}
\frac{d}{dr}\left(\frac{\rho r^2}{P}\frac{dc_s^2}{dr}\frac{\xi_{\ell m}}{r}\right)-\frac{\omega^2\rho r^2\xi_{\ell m}}{G} = -\frac{\rho}{P}\frac{\partial}{\partial r}\left(r^2\frac{d\Phi}{dr}\right)S_{\ell m}(r)
\end{equation}

转换后效果 #

To simplify the equation, we can assume that the perturbation of the Lagrangian displacement is proportional to a spherical harmonic function, $Y_{\ell m}(\theta,\phi)$, where $\ell$ is the degree of the harmonic and $m$ is the azimuthal order. Then, we can write:

\begin{equation}
\xi(r,\theta,\phi) = \sum_{\ell=0}^{\infty}\sum_{m=-\ell}^{\ell} \xi_{\ell m}(r) Y_{\ell m}(\theta,\phi)
\end{equation}

\noindent
Substituting this expression into the equation of motion, we obtain:

\begin{equation}
\frac{d}{dr}\left(\frac{\rho r^2}{P}\frac{dc_s^2}{dr}\frac{\xi_{\ell m}}{r}\right)-\frac{\omega^2\rho r^2\xi_{\ell m}}{G} = -\frac{\rho}{P}\frac{\partial}{\partial r}\left(r^2\frac{d\Phi}{dr}\right)S_{\ell m}(r)
\end{equation}

内容的提问来源于stack exchange，提问作者Mare Dedeu