GUN Sed Bug

[王森]

Hi
### tmp.txt ###
address@hidden learn_sed]# cat tmp.txt
hello world
I'am in china
address@hidden learn_sed]#
address@hidden learn_sed]# sed --version
GNU sed version 4.2.1
address@hidden learn_sed]# which sed
/bin/sed
address@hidden learn_sed]# /bin/sed 's/$/ End/' tmp.txt
hello world End
I'am in china End
address@hidden learn_sed]#
address@hidden learn_sed]#
address@hidden learn_sed]# /bin/sed "s/\'/ End/" tmp.txt
hello world End
I'am in china End
address@hidden learn_sed]#
### My Question
I want to know the reason.  \' be equal to Line End ?
If possible , tell me why ?   thanks