go/src/os/env.go

// Expand replaces ${var} or $var in the string based on the mapping function.
// For example, [os.ExpandEnv](s) is equivalent to [os.Expand](s, [os.Getenv]).
func Expand(s string, mapping func(string) string) string { … }

// ExpandEnv replaces ${var} or $var in the string according to the values
// of the current environment variables. References to undefined
// variables are replaced by the empty string.
func ExpandEnv(s string) string { … }

// isShellSpecialVar reports whether the character identifies a special
// shell variable such as $*.
func isShellSpecialVar(c uint8) bool { … }

// isAlphaNum reports whether the byte is an ASCII letter, number, or underscore.
func isAlphaNum(c uint8) bool { … }

// getShellName returns the name that begins the string and the number of bytes
// consumed to extract it. If the name is enclosed in {}, it's part of a ${}
// expansion and two more bytes are needed than the length of the name.
func getShellName(s string) (string, int) { … }

// Getenv retrieves the value of the environment variable named by the key.
// It returns the value, which will be empty if the variable is not present.
// To distinguish between an empty value and an unset value, use [LookupEnv].
func Getenv(key string) string { … }

// LookupEnv retrieves the value of the environment variable named
// by the key. If the variable is present in the environment the
// value (which may be empty) is returned and the boolean is true.
// Otherwise the returned value will be empty and the boolean will
// be false.
func LookupEnv(key string) (string, bool) { … }

// Setenv sets the value of the environment variable named by the key.
// It returns an error, if any.
func Setenv(key, value string) error { … }

// Unsetenv unsets a single environment variable.
func Unsetenv(key string) error { … }

// Clearenv deletes all environment variables.
func Clearenv() { … }

// Environ returns a copy of strings representing the environment,
// in the form "key=value".
func Environ() []string { … }