DockerCLI/opts/envfile.go

62 lines
1.7 KiB
Go

package opts
import (
"bufio"
"fmt"
"os"
"regexp"
"strings"
)
var (
// EnvironmentVariableRegexp A regexp to validate correct environment variables
// Environment variables set by the user must have a name consisting solely of
// alphabetics, numerics, and underscores - the first of which must not be numeric.
EnvironmentVariableRegexp = regexp.MustCompile("^[[:alpha:]_][[:alpha:][:digit:]_]*$")
)
// ParseEnvFile Read in a line delimited file with environment variables enumerated
func ParseEnvFile(filename string) ([]string, error) {
fh, err := os.Open(filename)
if err != nil {
return []string{}, err
}
defer fh.Close()
lines := []string{}
scanner := bufio.NewScanner(fh)
for scanner.Scan() {
// trim the line from all leading whitespace first
line := strings.TrimLeft(scanner.Text(), whiteSpaces)
// line is not empty, and not starting with '#'
if len(line) > 0 && !strings.HasPrefix(line, "#") {
data := strings.SplitN(line, "=", 2)
variable := data[0]
if !EnvironmentVariableRegexp.MatchString(variable) {
return []string{}, ErrBadEnvVariable{fmt.Sprintf("variable '%s' is not a valid environment variable", variable)}
}
if len(data) > 1 {
// pass the value through, no trimming
lines = append(lines, fmt.Sprintf("%s=%s", variable, data[1]))
} else {
// if only a pass-through variable is given, clean it up.
lines = append(lines, fmt.Sprintf("%s=%s", strings.TrimSpace(line), os.Getenv(line)))
}
}
}
return lines, scanner.Err()
}
var whiteSpaces = " \t"
// ErrBadEnvVariable typed error for bad environment variable
type ErrBadEnvVariable struct {
msg string
}
func (e ErrBadEnvVariable) Error() string {
return fmt.Sprintf("poorly formatted environment: %s", e.msg)
}