${1+"$@"} 和 "$@"有何区别？

飞灰橙

看到/bin/egrep实际为
exec grep -E ${1+"$@"}

为什么不直接写
exec grep -E "$@"
呢？
百思不得其解。

c1l2d3

飞兄的问题要我来回答：

就一个字“ 顶”  ^_^

飞灰橙

小弟试了很多参数，都没有发现不同。
还是仅仅为了保险起见?

r2007

这有一段老外的帖子

1. > egrep: #!/bin/sh
   
2. >  exec grep -E ${1+"$@"}
   
3. >
   
4. > The parameter is just an improved replacement of the traditional $*, this is OK.
   
5. > (BTW: I don't understand why simple "$@" is not enough.)
   
6. 
   
7. Some shells expand "$@" like "" (a single empty argument) when there
   
8. are no arguments.  ${1+"$@"} correctly expands to no arguments on
   
9. those shells.
   
10. 
    
11. However, it breaks on zsh, which is used as /bin/sh on Mac OS X,
    
12. unless you first do:
    
13. case "$ZSH_VERSION" in ?*) alias -g '${1+"$@"}'='"$@"';; esac

复制代码

飞灰橙

小弟明白了，多谢各位。