mirror of
https://github.com/golang/go
synced 2024-10-04 12:31:21 -06:00
707e5acd71
(more are possible but omitted for now as they are part of specific tests where rather than changing what is there we should probably expand the tests to cover the new case) R=rsc, dvyukov CC=golang-dev https://golang.org/cl/5247058
76 lines
2.2 KiB
Go
76 lines
2.2 KiB
Go
// Copyright 2010 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// General environment variables.
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package os
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func setenv_c(k, v string)
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// Expand replaces ${var} or $var in the string based on the mapping function.
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// Invocations of undefined variables are replaced with the empty string.
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func Expand(s string, mapping func(string) string) string {
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buf := make([]byte, 0, 2*len(s))
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// ${} is all ASCII, so bytes are fine for this operation.
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i := 0
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for j := 0; j < len(s); j++ {
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if s[j] == '$' && j+1 < len(s) {
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buf = append(buf, s[i:j]...)
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name, w := getShellName(s[j+1:])
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buf = append(buf, mapping(name)...)
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j += w
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i = j + 1
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}
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}
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return string(buf) + s[i:]
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}
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// ShellExpand replaces ${var} or $var in the string according to the values
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// of the operating system's environment variables. References to undefined
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// variables are replaced by the empty string.
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func ShellExpand(s string) string {
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return Expand(s, Getenv)
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}
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// isSpellSpecialVar reports whether the character identifies a special
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// shell variable such as $*.
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func isShellSpecialVar(c uint8) bool {
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switch c {
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case '*', '#', '$', '@', '!', '?', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
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return true
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}
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return false
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}
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// isAlphaNum reports whether the byte is an ASCII letter, number, or underscore
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func isAlphaNum(c uint8) bool {
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return c == '_' || '0' <= c && c <= '9' || 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z'
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}
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// getName returns the name that begins the string and the number of bytes
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// consumed to extract it. If the name is enclosed in {}, it's part of a ${}
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// expansion and two more bytes are needed than the length of the name.
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func getShellName(s string) (string, int) {
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switch {
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case s[0] == '{':
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if len(s) > 2 && isShellSpecialVar(s[1]) && s[2] == '}' {
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return s[1:2], 3
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}
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// Scan to closing brace
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for i := 1; i < len(s); i++ {
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if s[i] == '}' {
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return s[1:i], i + 1
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}
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}
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return "", 1 // Bad syntax; just eat the brace.
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case isShellSpecialVar(s[0]):
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return s[0:1], 1
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}
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// Scan alphanumerics.
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var i int
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for i = 0; i < len(s) && isAlphaNum(s[i]); i++ {
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}
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return s[:i], i
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}
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