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envfile.go
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envfile.go
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package opts
import (
"bufio"
"bytes"
"fmt"
"os"
"strings"
"unicode"
"unicode/utf8"
)
// ParseEnvFile reads a file with environment variables enumerated by lines
//
// ``Environment variable names used by the utilities in the Shell and
// Utilities volume of IEEE Std 1003.1-2001 consist solely of uppercase
// letters, digits, and the '_' (underscore) from the characters defined in
// Portable Character Set and do not begin with a digit. *But*, other
// characters may be permitted by an implementation; applications shall
// tolerate the presence of such names.''
// -- http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap08.html
//
// As of #16585, it's up to application inside docker to validate or not
// environment variables, that's why we just strip leading whitespace and
// nothing more.
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)
currentLine := 0
utf8bom := []byte{0xEF, 0xBB, 0xBF}
for scanner.Scan() {
scannedBytes := scanner.Bytes()
if !utf8.Valid(scannedBytes) {
return []string{}, fmt.Errorf("env file %s contains invalid utf8 bytes at line %d: %v", filename, currentLine+1, scannedBytes)
}
// We trim UTF8 BOM
if currentLine == 0 {
scannedBytes = bytes.TrimPrefix(scannedBytes, utf8bom)
}
// trim the line from all leading whitespace first
line := strings.TrimLeftFunc(string(scannedBytes), unicode.IsSpace)
currentLine++
// line is not empty, and not starting with '#'
if len(line) > 0 && !strings.HasPrefix(line, "#") {
data := strings.SplitN(line, "=", 2)
// trim the front of a variable, but nothing else
variable := strings.TrimLeft(data[0], whiteSpaces)
if strings.ContainsAny(variable, whiteSpaces) {
return []string{}, ErrBadEnvVariable{fmt.Sprintf("variable '%s' has white spaces", 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)
}