difference sed on macosx and linux

sed正则替换内容时，碰到在Linux上正常执行的命令在MacOSX执行失败的问题，如：

 sed -i 's/text/replaced/g' filename

sed: 1: "filename": invalid command code -

google之后发现有别人碰到类似的问题，在MacOSX上需要加个空字符串在-i参数后面：

 sed -i "" 's/text/relpaced/g' filename

What I hadn’t realised is that on the Mac version of sed the -i flag has a mandatory suffix, as described in this post.

The appropriate section of the man page for sed on the Mac looks like this:

-i extension
    Edit files in-place, saving backups with the specified extension. If a zero-length extension is given, no backup will be saved.

It is not recommended togive a zero-length extension when in-place editing files, as you risk corruption or partial content in situations where disk space is exhausted, etc.

Whereas on Ubuntu the suffix is optional so we see this:

-i[SUFFIX], –in-place[=SUFFIX]
    edit files in place (makes backup if extension supplied)

In order to get around this we need to provide a blank suffix when using the -i flag on the Mac: