script_parse.go

package runtime

// parse parses a single line as a list of space-separated arguments
// subject to environment variable expansion (but not resplitting).
// Single quotes around text disable splitting and expansion.
// To embed a single quote, double it: 'Don''t communicate by sharing memory.'
func (ts *Script) parse(line string) []string {
	ts.line = line

	var (
		args   []string
		arg    string  // text of current arg so far (need to add line[start:i])
		start  = -1    // if >= 0, position where current arg text chunk starts
		quoted = false // currently processing quoted text
	)
	for i := 0; ; i++ {
		if !quoted && (i >= len(line) || line[i] == ' ' || line[i] == '\t' || line[i] == '\r' || line[i] == '#') {
			// Found arg-separating space.
			if start >= 0 {
				arg += ts.expand(line[start:i])
				args = append(args, arg)
				start = -1
				arg = ""
			}
			if i >= len(line) || line[i] == '#' {
				break
			}
			continue
		}
		if i >= len(line) {
			ts.Fatalf("unterminated quoted argument")
		}
		if line[i] == '\'' {
			if !quoted {
				// starting a quoted chunk
				if start >= 0 {
					arg += ts.expand(line[start:i])
				}
				start = i + 1
				quoted = true
				continue
			}
			// 'foo''bar' means foo'bar, like in rc shell and Pascal.
			if i+1 < len(line) && line[i+1] == '\'' {
				arg += line[start:i]
				start = i + 1
				i++ // skip over second ' before next iteration
				continue
			}
			// ending a quoted chunk
			arg += line[start:i]
			start = i + 1
			quoted = false
			continue
		}
		// found character worth saving; make sure we're saving
		if start < 0 {
			start = i
		}
	}
	return args
}