在 shell 脚本中拆分文件会添加不需要的换行符

Question

我需要处理一个长文本文件，将其拆分为许多较小的文件。我有一个单程 while - read - done 循环，当匹配一行时，表示新输出文件的开始。在输入文件中，匹配的行总是以换行符开头。

我的问题是输出文件（除了最后一个）被换行符扩展。我在这个简短的例子中重现了这个问题。

#!/bin/zsh

rm inputfile outputfile1 outputfile2
IFS=''
printf "section1\nsection1end\n\nsection2\nsection2end\n" >inputfile

echo "  open outputfile1"
exec 3<> outputfile1
counter=1
IFS=$'\n'

while IFS= read line; do

    if [[ "$line" == "section2" ]]; then
        echo "  Matched start of section2. Close outputfile1 and open outputfile2"
        exec 3>&-
        exec 3<> outputfile2
    fi
    echo "$line" >&3
    echo $counter $line
    let "counter = $counter + 1"
done <inputfile
echo "  Close outputfile2"
exec 3>&-

echo
unset IFS
echo `wc -l inputfile`
echo `wc -l outputfile1`
echo `wc -l outputfile2`
echo "  The above should show 5, 2, 2 as desired number of newlines in these files."

哪些输出：

  open outputfile1
1 section1
2 section1end
3
  Matched start of section2. Close outputfile1 and open outputfile2
4 section2
5 section2end
  Close outputfile2

5 inputfile
3 outputfile1
2 outputfile2
  The above should show 5, 2, 2 as desired number of newlines in these files.

Answer 1

选项 1

去掉所有空行。这仅在您不需要在部分中间保留任何空行时才有效。 变化：

    echo "$line" >&3

收件人：

    [[ -n "$line" ]] && echo "$line" >&3

选项 2

使用命令替换重写每个文件以修剪任何尾随换行符。最适合短文件。变化：

        exec 3>&-
        exec 3<> outputfile2

收件人：

        exec 3>&-
        data=$(<outputfile1)
        echo "$data" >outputfile1
        exec 3<> outputfile2

选项 3

让循环写入前一次迭代的行，然后在开始新文件时不要写入前一个文件的最后一行：

#!/bin/zsh

rm inputfile outputfile1 outputfile2
IFS=''
printf "section1\nsection1end\n\nsection2\nsection2end\n" >inputfile

echo "  open outputfile1"
exec 3<> outputfile1
counter=1
IFS=$'\n'

priorLine=MARKER
while IFS= read line; do
    if [[ "$line" == "section2" ]]; then
        echo "  Matched start of section2. Close outputfile1 and open outputfile2"
        exec 3>&-
        exec 3<> outputfile2
    elif [[ "$priorLine" != MARKER ]]; then
        echo "$priorLine" >&3
    fi
    echo $counter $line
    let "counter = $counter + 1"
    priorLine="$line"
done <inputfile
echo "$priorLine" >&3
echo "  Close outputfile2"
exec 3>&-

echo
unset IFS
echo `wc -l inputfile`
echo `wc -l outputfile1`
echo `wc -l outputfile2`
echo "  The above should show 5, 2, 2 as desired number of newlines in these files."