sed 命令的奇怪行为

Question

谁能解释一下 sed 的这种行为？

cat -bash-3.2# cat tmp7

echo "this is the song that never ends
yes, it goes on and on, my friend
some people started singing it
not knowing what it was
and they'll continue singing it forever
just because..." >

-bash-3.2# sed -n 's_.*some\(.*\)started.*__p' tmp7

输出

people

-bash-3.2# cat tmp8
echo "this is the song that never endsyes, it goes on and on, my friendsome people started singing itnot knowing what it wasand they'll continue singing it foreverjust because..." >

sed -n 's_.*some\(.*\)started.*__p' tmp8

什么都不输出

我希望第二个命令的输出应该与第一个命令相同。

文件tmp7和tmp8的内容是一样的，唯一的区别是tmp7包含换行符而tmp8没有。

更新

尝试使用不同版本的 sed /usr/xpg4/bin/sed，获得了理想的输出，但出现警告 sed: Missing newline at end of file tmp8.。我想要没有警告的输出。

  /usr/xpg4/bin/sed -n 's_.*some\(.*\)started.*__p' tmp8

   sed: Missing newline at end of file tmp8.
   people

Answer 1

Solaris 默认 sed 忽略最后一行不破坏现有脚本，因为在原始 Unix 实现中要求一行以新行终止。

GNU sed 有更宽松的行为，POSIX 实现接受事实但输出警告。您可以将 stderr 重定向到 /dev/null 以忽略它。

/usr/xpg4/bin/sed -n 's_.*some\(.*\)started.*__p' tmp8 2>/dev/null

sed 命令的奇怪行为

strange behaviour of sed command

bash

sed

solaris