杂：使用Shell判断文件换行符(LF/CRLF)

前提：文件最后一行有换行符

第一步：以二进制方式取得文件最后两个byte。
last2=`tail -c 2 <your_file> | od -x -A n`

第二步：判断最后两个byte是否是'CRLF'
if [ $last2 = 0a0d -o $last2 = 0d0a ]
then
# Cheating! If the file ends in LFCR, it would incorrectly
# say that it is CRLF
echo File ends in CRLF
fi

---

另外，下面这种方法的原理，让人百思不得其姐，
#重定向标准输入
exec < <your_file>
read -r line
case $line in *$'\r') return 1;; *) return 0;; esac

原以为read加了-r就可以把$'\n'读出来，实际上却是用read把末尾的$'\n'先去掉，剩下的如果是$'\r'就认为是'CRLF'换行。
这个语句表明read一定会去掉末尾的$'\n'

PS:Shell里$'\r'和$'\n'就这么写

---

完整代码

#!/bin/bash

if [ $# -eq 0 ] ; then
echo "error : there is no para"
exit 1
fi

if [ ! -e $1 ] ; then
echo "file $1 is not exist"
exit 1
fi

last2=$(tail -c 2 "$1" | od -x -A n)

if [ $last2 = 0a0d -o $last2 = 0d0a ] ; then
echo "end with \\r\\n"
else
echo "end with \\n"
fi

---

遍历文件夹版

#!/bin/bash

#func check CRLF bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
check_CRLF(){
last2=$(tail -c 2 "$1" | od -x -A n)

echo "last2 is $last2"
if [ $last2 = 0a0d -o $last2 = 0d0a ] ; then
echo "warning! file $1 end with \\r\\n"
else
echo "file $1 end with \\n"
fi
}

#func traverse folder bbbbbbbbbbbbbbbbbbbbbbbbbbbb
traverse_folder(){

# no para
if [ $# -eq 0 ]; then
exit 1
fi

# not folder
if [ ! -d $1 ]; then
exit 1
fi

# traversal
for files_or_folder in $1/*
do
# is file
if [ -f $files_or_folder ]; then
check_CRLF $files_or_folder
# is folder
elif [ -d $files_or_folder ]; then
traverse_folder $files_or_folder
else
exit 1
fi
done
}

#bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
if [ $# -eq 0 ] ; then
echo "error : there is no para"
exit
fi

traverse_folder $1

---

一句搞定版

find . -type f | xargs file | grep CRLF