bash BASH中“${1#*-}”是什么意思
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What is the meaning of "${1#*-}" in BASH
提问by rɑ?d?ɑ
There is a if condition as below
有一个 if 条件如下
if [ "${1#*-}" = "" ]; then
echo "Do something"
fi
But could somebody explain what is the meaning of ${1#*-}?
但是有人能解释一下是什么意思${1#*-}吗？
回答by Kent
${1#*-}deletes the shortest match of *-, a glob-like pattern from $1variable.
${1#*-}*-从$1变量中删除 的最短匹配项，一个类似 glob 的模式。
E.g. abcdef-xyz-foo-> xyz-foo
例如abcdef-xyz-foo->xyz-foo
Your ifcheck does actually:
您的if支票实际上是：
if does not contain '-'
回答by chepner
*-is a pattern matching a (possibly empty) string followed by a -. The #operator drops the shortestprefix matching *-from the expansion of $1. An example:
*-是一个匹配（可能为空）字符串后跟一个的模式-。该#运营商下降到最短前缀匹配*-，从扩张$1。一个例子：
$ foo="123-456"
$ echo "${foo#*-}"
456
$ foo="123-456-789"
456-789
I emphasize shortest because there is a companion operator ##that drops the longestmatching prefix.
我强调最短是因为有一个伴随运算符##丢弃最长的匹配前缀。
$ echo "${foo##*-}"
789
回答by Jhonatan
This test if no have "-"in a parameter 1
此测试是否"-"在参数 1 中没有
See this:
看到这个：
test=jhonatan
if [ "${test#*-}" = "$test" ]; then
echo "yes" ;
else
echo "no" ;
fi
This print yes because no have "-"in a string test
这个打印是因为"-"在字符串测试中没有
with this
有了这个
test=jhonatan-piffer
The same script print no.
相同的脚本打印没有。
${variable#pattern}remove prefix pattern of string.
${variable#pattern}删除字符串的前缀模式。
In this last case all string between start until "-"
在最后一种情况下，开始到之间的所有字符串 "-"
echo ${test#*-}
result in:
导致：
"piffer"
and "piffer"differs from "jhonatan-piffer"
并且"piffer"不同于"jhonatan-piffer"
Read this for more information: https://www.gnu.org/software/bash/manual/bash.html#Shell-Parameter-Expansion
阅读更多信息：https: //www.gnu.org/software/bash/manual/bash.html#Shell-Parameter-Expansion
