1. Path包概要
1.1 概述
Package path implements utility routines for manipulating slash-separated paths.
path 包实现了对以/为分隔的路径的操作
The path package should only be used for paths separated by forward slashes, such as the paths in URLs. This package does not deal with Windows paths with drive letters or backslashes; to manipulate operating system paths, use the path/filepath package.
该包只能用于对以正斜杠/为分隔的路径的处理，比如 URL，而不能处理带有windows中的盘符或者反斜杠\的路径，对于这类路径的处理需要使用 path/filepath 包
1.2 包结构
├── example_test.go
├── match.go
├── match_test.go
├── path.go
└── path_test.go
2. 深入path包
2.1 path.go & path_test.go
2.1.1 Clean
签名：func Clean(path string) string
用途：Clean函数主要是对给定路径进行以下格式化：
- 替换多个斜杠
//为单个斜杠/ - 消除
. - 消除
..当且仅当前一个元素不是.. - 替换绝对路径开头的
/..为/ - 格式化后的路径不以
/结尾，除非该路径就是根路径/ - 若格式化后路径为空，则返回
.
示例：https://play.golang.org/p/Ya85iuk0uMU
// Already clean
"" => "."
"abc" => "abc"
"abc/def" => "abc/def"
"a/b/c" => "a/b/c"
"." => "."
".." => ".."
"../.." => "../.."
"../../abc" => "../../abc"
"/abc" => "/abc"
"/" => "/"
// Remove trailing slash
"abc/" => "abc"
"abc/def/" => "abc/def"
"a/b/c/" => "a/b/c"
"./" => "."
"../" => ".."
"../../" => "../.."
"/abc/" => "/abc"
// Remove doubled slash
"abc//def//ghi" => "abc/def/ghi"
"//abc" => "/abc"
"///abc" => "/abc"
"//abc//" => "/abc"
"abc//" => "abc"
"abc/./def" => "abc/def"
"/./abc/def" => "/abc/def"
"abc/." => "abc"
// Remove .. elements
"abc/def/ghi/../jkl" => "abc/def/jkl"
"abc/def/../ghi/../jkl" => "abc/jkl"
"abc/def/.." => "abc"
"abc/def/../.." => "."
"/abc/def/../.." => "/"
"abc/def/../../.." => ".."
"/abc/def/../../.." => "/"
"abc/def/../../../ghi/jkl/../../../mno" => "../../mno"
// Combinations
"abc/./../def" => "def"
"abc//./../def" => "def"
"abc/../../././../def" => "../../def"
2.1.2 Split
签名：func Split(path string) (dir, file string)
用途：拆分路径为目录+文件，目录保留/，若路径中没有/，则目录为空
示例：https://play.golang.org/p/DG8QjjWdkuq
"a/b" => "a/" + "b"
"a/b/" => "a/b/" + ""
"a/" => "a/" + ""
"a" => "" + "a"
"/" => "/" + ""
2.1.3 Join
签名：Join(elem ...string) string
用途：把所有元素按顺序拼接为路径，并对路径格式化
示例：https://play.golang.org/p/jxcwt_fgUpt
// zero parameters
{[]string{} => ""},
// one parameter
{[]string{""} => ""},
{[]string{"a"} => "a"},
// two parameters
{[]string{"a", "b"} => "a/b"},
{[]string{"a", ""} => "a"},
{[]string{"", "b"} => "b"},
{[]string{"/", "a"} => "/a"},
{[]string{"/", ""} => "/"},
{[]string{"a/", "b"} => "a/b"},
{[]string{"a/", ""} => "a"},
{[]string{"", ""} => ""},
2.1.4 Ext
签名：Ext(path string) string
用途：根据.返回路径中文件的扩展名，若没有.则返回空
示例：https://play.golang.org/p/VxIO_oewphL
{"path.go" => ".go"},
{"path.pb.go" => ".go"},
{"a.dir/b" => ""},
{"a.dir/b.go" => ".go"},
{"a.dir/" => ""},
2.1.5 Base
签名：Base(path string) string
用途：先清除路径末尾的/（如果有的话），再根据最后一个/，返回该元素，若没有/，则返回.
示例：https://play.golang.org/p/bW-KYszq1fE
{"" => "."},
{"." => "."},
{"/." => "."},
{"/" => "/"},
{"////" => "/"},
{"x/" => "x"},
{"abc" => "abc"},
{"abc/def" => "def"},
{"a/b/.x" => ".x"},
{"a/b/c." => "c."},
{"a/b/c.x" => "c.x"},
2.1.6 IsAbs
签名：IsAbs(path string) bool
用途：判断路径是否为绝对路径，即以/开头
示例：https://play.golang.org/p/MWv0m9Q8I-J
{"" => false},
{"/" => true},
{"/usr/bin/gcc" => true},
{".." => false},
{"/a/../bb" => true},
{"." => false},
{"./" => false},
{"lala" => false},
2.1.7 Dir
签名：Dir(path string) string
用途：返回去除最后一项后的目录路径,并格式化
示例：https://play.golang.org/p/DBULKf343C6
{"" => "."},
{"." => "."},
{"/." => "/"},
{"/" => "/"},
{"////" => "/"},
{"/foo" => "/"},
{"x/" => "x"},
{"abc" => "."},
{"abc/def" => "abc"},
{"abc////def" => "abc"},
{"a/b/.x" => "a/b"},
{"a/b/c." => "a/b"},
{"a/b/c.x" => "a/b"},
2.2 match.go & match_test.go
2.2.1 Match
签名：func Match(pattern, name string) (matched bool, err error)
用途：根据给定的模式对路径进行匹配，模式如下：
pattern:
{ term }
term:
'*' matches any sequence of non-/ characters 匹配任意数量的所有非/字符
'?' matches any single non-/ character 匹配所有单个非/字符
'[' [ '^' ] { character-range } ']' 区间匹配，^表示除了该区间，匹配不能为空，至少需要一个
character class (must be non-empty)
c matches character c (c != '*', '?', '\\', '[') 匹配单个确定字符，除'*', '?', '\\', '['
'\\' c matches character c 可以看作转义匹配'*', '?', '\\', '['
character-range:
c matches character c (c != '\\', '-', ']') 在区间匹配中匹配单个确定字符，除'\\', '-', ']'
'\\' c matches character c 可以看作在区间匹配中转义匹配'\\', '-', ']'
lo '-' hi matches character c for lo <= c <= hi 区间范围
示例：https://play.golang.org/p/yhfME8jBmn1
{"abc", "abc", true, nil},
{"*", "abc", true, nil},
{"*c", "abc", true, nil},
{"a*", "a", true, nil},
{"a*", "abc", true, nil},
{"a*", "ab/c", false, nil},
{"a*/b", "abc/b", true, nil},
{"a*/b", "a/c/b", false, nil},
{"a*b*c*d*e*/f", "axbxcxdxe/f", true, nil},
{"a*b*c*d*e*/f", "axbxcxdxexxx/f", true, nil},
{"a*b*c*d*e*/f", "axbxcxdxe/xxx/f", false, nil},
{"a*b*c*d*e*/f", "axbxcxdxexxx/fff", false, nil},
{"a*b?c*x", "abxbbxdbxebxczzx", true, nil},
{"a*b?c*x", "abxbbxdbxebxczzy", false, nil},
{"ab[c]", "abc", true, nil},
{"ab[b-d]", "abc", true, nil},
{"ab[e-g]", "abc", false, nil},
{"ab[^c]", "abc", false, nil},
{"ab[^b-d]", "abc", false, nil},
{"ab[^e-g]", "abc", true, nil},
{"a\\*b", "a*b", true, nil},
{"a\\*b", "ab", false, nil},
{"a?b", "a☺b", true, nil},
{"a[^a]b", "a☺b", true, nil},
{"a???b", "a☺b", false, nil},
{"a[^a][^a][^a]b", "a☺b", false, nil},
{"[a-ζ]*", "α", true, nil},
{"*[a-ζ]", "A", false, nil},
{"a?b", "a/b", false, nil},
{"a*b", "a/b", false, nil},
{"[\\]a]", "]", true, nil},
{"[\\-]", "-", true, nil},
{"[x\\-]", "x", true, nil},
{"[x\\-]", "-", true, nil},
{"[x\\-]", "z", false, nil},
{"[\\-x]", "x", true, nil},
{"[\\-x]", "-", true, nil},
{"[\\-x]", "a", false, nil},
{"[]a]", "]", false, ErrBadPattern},
{"[-]", "-", false, ErrBadPattern},
{"[x-]", "x", false, ErrBadPattern},
{"[x-]", "-", false, ErrBadPattern},
{"[x-]", "z", false, ErrBadPattern},
{"[-x]", "x", false, ErrBadPattern},
{"[-x]", "-", false, ErrBadPattern},
{"[-x]", "a", false, ErrBadPattern},
{"\\", "a", false, ErrBadPattern},
{"[a-b-c]", "a", false, ErrBadPattern},
{"[", "a", false, ErrBadPattern},
{"[^", "a", false, ErrBadPattern},
{"[^bc", "a", false, ErrBadPattern},
{"a[", "a", false, nil},
{"a[", "ab", false, ErrBadPattern},
{"*x", "xxx", true, nil},