Linux-Shell脚本中％和%%有什么区别？

在bash脚本中,当t =“ hello.txt”都

${t %%.txt}和${t％.txt}返回“ hello”

${t ## *.}也是一样,${t#*.}返回“ txt”.

它们之间有区别吗？它们如何工作？

解决方法:

简而言之,%%尽可能多地去除,％尽可能少地去除.

# t="hello.world.txt"
# echo ${t%.*}
hello.world
# echo ${t%%.*}
hello

从bash手册中：

'${ParaMETER%WORD}'
'${ParaMETER%%WORD}'
     The WORD is expanded to produce a pattern just as in filename
     expansion.  If the pattern matches a trailing portion of the
     expanded value of ParaMETER, then the result of the expansion is
     the value of ParaMETER with the shortest matching pattern (the '%'
     case) or the longest matching pattern (the '%%' case) deleted.  If
     ParaMETER is '@' or '*', the pattern removal operation is applied
     to each positional parameter in turn, and the expansion is the
     resultant list.  If ParaMETER is an array variable subscripted with
     '@' or '*', the pattern removal operation is applied to each member
     of the array in turn, and the expansion is the resultant list.