Florian.Walther/gosh
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add assignments name=value and unset

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- name=value (one or more) without a command sets variables of the shell
- name=value before a command sets them only in its environment (for
  builtins only while they run)
- an assignment needs an unquoted name and =; the value is not split
  and not expanded as wildcard or brace pattern, ~ is expanded after =
  and :
- the status of an assignment is the one of its last $(...)
- new builtin unset

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
Florian WaltherandClaude Opus 5.5 committed 2026-10-04 00:17:38 +02:00
1 parent fb94e98da5
commit 22ce8c00d4
5 files changed
+256 -14
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main.go
+98 -9
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@@ -121,6 +121,7 @@ type token struct {
word string // the word, if op == ""
pattern string // the word as glob pattern (quoted characters escaped)
glob bool // the word contains unquoted * ? or [ and is expanded
assign bool // the word is an assignment name=value (unquoted name and =)
fd int // the redirected file descriptor (for redirections)
dup int // the target file descriptor of >& and <&
}
@@ -136,7 +137,8 @@ type token struct {
// - $VAR, ${VAR} and ${VAR:-default} are expanded outside single quotes;
// an unset variable is an error, so that e.g. "rm -rf $DIR/x" never runs
// with an empty $DIR
// - ~ and ~/... are expanded at the start of an unquoted word
// - ~ and ~/... are expanded at the start of an unquoted word, and after
// the = and : of an assignment (PATH=~/bin:~/go/bin)
// - unquoted |, <, >, >>, N<, N>, N>>, N>&M, N<&M, &> and &>> are operators
//
// Expanded values are never split into several words.
@@ -147,6 +149,9 @@ func tokenize(input string) ([]token, error) {
pat strings.Builder // the word as glob pattern, quoted parts escaped
glob bool // the word contains unquoted * ? or [
inWord bool // a word has been started (even if it is still empty)
plain = true // the word so far has no quotes, escapes or expansions
assign bool // the word is an assignment name=value
tildeOK bool // ~ may be expanded here (after = or : of an assignment)
quote byte
escaped bool
rawStart = -1 // start of the current word in input
@@ -154,16 +159,17 @@ func tokenize(input string) ([]token, error) {
endWord := func() {
if inWord {
tokens = append(tokens, token{word: b.String(), pattern: pat.String(), glob: glob})
tokens = append(tokens, token{word: b.String(), pattern: pat.String(), glob: glob, assign: assign})
}
b.Reset()
pat.Reset()
glob = false
glob, assign, plain = false, false, true
inWord = false
rawStart = -1
}
// literal adds quoted, escaped or expanded text: it is never a pattern
literal := func(s string) {
plain = false
b.WriteString(s)
pat.WriteString(escapeGlob(s))
}
@@ -175,6 +181,8 @@ func tokenize(input string) ([]token, error) {
for i := 0; i < len(input); i++ {
ch := input[i]
afterAssignSep := tildeOK
tildeOK = false
switch {
case escaped:
if quote == '"' && !strings.ContainsRune("$\"\\`", rune(ch)) {
@@ -202,7 +210,8 @@ func tokenize(input string) ([]token, error) {
if err != nil {
return nil, err
}
if quote == '"' {
if quote == '"' || assign {
// Quoted or in an assignment, the output is one word
literal(out)
inWord = true
} else {
@@ -241,6 +250,7 @@ func tokenize(input string) ([]token, error) {
}
case ch == '"' || ch == '\'':
startRaw(i)
plain = false
quote = ch
inWord = true
case ch == ' ' || ch == '\t' || ch == '\n':
@@ -296,8 +306,8 @@ func tokenize(input string) ([]token, error) {
i = j - 1
}
tokens = append(tokens, t)
case ch == '~' && !inWord && b.Len() == 0 &&
(i+1 == len(input) || strings.IndexByte("/ \t\n|<>", input[i+1]) >= 0):
case ch == '~' && (!inWord && b.Len() == 0 || afterAssignSep) &&
(i+1 == len(input) || strings.IndexByte("/ \t\n|<>:", input[i+1]) >= 0):
startRaw(i)
home := getHomeDir()
if home == "" {
@@ -307,6 +317,14 @@ func tokenize(input string) ([]token, error) {
inWord = true
default:
startRaw(i)
switch {
case ch == '=' && plain && !assign && isVarName(b.String()):
// name=value; ~ may follow
assign, tildeOK = true, true
case ch == ':' && assign:
// PATH=~/bin:~/go/bin
tildeOK = true
}
b.WriteByte(ch)
switch {
case ch == '*' || ch == '?' || ch == '[':
@@ -742,7 +760,7 @@ type shellCompleter struct {
func newShellCompleter() *shellCompleter {
return &shellCompleter{
commands: []string{"cd", "pwd", "echo", "exit", "quit", "set", "export", "source", "jobs", "fg", "bg", "wait", "alias", "unalias", "break", "continue", "help"},
commands: []string{"cd", "pwd", "echo", "exit", "quit", "set", "export", "source", "jobs", "fg", "bg", "wait", "alias", "unalias", "break", "continue", "unset", "help"},
}
}
@@ -1391,6 +1409,7 @@ type redirect struct {
// stage is a simple command of a pipeline.
type stage struct {
assigns []string // name=value before the command name
args []string
redirects []redirect
}
@@ -1401,13 +1420,18 @@ func parsePipeline(tokens []token) ([]stage, error) {
stages []stage
cur stage
)
isEmpty := func(s stage) bool { return len(s.args) == 0 && len(s.redirects) == 0 }
isEmpty := func(s stage) bool { return len(s.assigns) == 0 && len(s.args) == 0 && len(s.redirects) == 0 }
for i := 0; i < len(tokens); i++ {
t := tokens[i]
switch t.op {
case "":
cur.args = append(cur.args, expandWord(t)...)
if t.assign && len(cur.args) == 0 {
// The value is not split and not expanded as a pattern
cur.assigns = append(cur.assigns, t.word)
} else {
cur.args = append(cur.args, expandWord(t)...)
}
case "|":
if isEmpty(cur) {
return nil, syntaxError("|")
@@ -1526,6 +1550,20 @@ func startStage(st stage, stdin, stdout *os.File, j *job, inPipeline, background
fds := [3]*os.File{stdin, stdout, os.Stderr}
opened, err := applyRedirects(&fds, st.redirects)
owned = append(owned, opened...)
if err == nil && len(st.args) == 0 && len(st.assigns) > 0 {
// Assignments without a command set variables of the shell (not in
// a pipeline or in the background, where sh runs them in a
// subshell). The status is the one of the last $(...) in them.
if !inPipeline && !background {
for _, a := range st.assigns {
name, value, _ := strings.Cut(a, "=")
os.Setenv(name, value)
}
}
if substStatus != 0 {
err = statusError(substStatus)
}
}
if err != nil || len(st.args) == 0 {
// A command without arguments only creates or truncates the files
closeOwned()
@@ -1552,6 +1590,8 @@ func startStage(st stage, stdin, stdout *os.File, j *job, inPipeline, background
return err
}
if !inPipeline && !background {
// name=value before a builtin applies only while it runs
defer setTemporarily(st.assigns)()
return finishedProc(run())
}
p := &proc{done: make(chan error, 1)}
@@ -1561,6 +1601,11 @@ func startStage(st stage, stdin, stdout *os.File, j *job, inPipeline, background
cmd := exec.Command(st.args[0], st.args[1:]...)
cmd.Stdin, cmd.Stdout, cmd.Stderr = fds[0], fds[1], fds[2]
if len(st.assigns) > 0 {
// name=value before a command is only in its environment (the
// last value of a name wins)
cmd.Env = append(os.Environ(), st.assigns...)
}
if jobControl {
// All processes of the job share a process group: the one of the
// first process. In the foreground, the first process makes its
@@ -1593,6 +1638,31 @@ func startStage(st stage, stdin, stdout *os.File, j *job, inPipeline, background
return &proc{cmd: cmd}
}
// setTemporarily sets the variables of the assignments and returns a
// function that restores the previous values.
func setTemporarily(assigns []string) func() {
type saved struct {
name, value string
ok bool
}
var restore []saved
for _, a := range assigns {
name, value, _ := strings.Cut(a, "=")
old, ok := os.LookupEnv(name)
restore = append(restore, saved{name, old, ok})
os.Setenv(name, value)
}
return func() {
for i := len(restore) - 1; i >= 0; i-- {
if r := restore[i]; r.ok {
os.Setenv(r.name, r.value)
} else {
os.Unsetenv(r.name)
}
}
}
}
// applyRedirects applies the redirections in order to fds (stdin, stdout,
// stderr) and returns the files it opened.
func applyRedirects(fds *[3]*os.File, redirects []redirect) ([]*os.File, error) {
@@ -1661,6 +1731,7 @@ var builtins = map[string]struct{ changesState bool }{
"alias": {},
"unalias": {changesState: true},
":": {},
"unset": {changesState: true},
"break": {changesState: true},
"continue": {changesState: true},
}
@@ -1745,6 +1816,20 @@ func runBuiltin(args []string, stdout io.Writer) error {
case ":":
// Does nothing, successfully (e.g. while :; do ...)
return nil
case "unset":
// unset NAME ... - remove variables
if len(args) < 2 {
return fmt.Errorf("usage: unset NAME ...")
}
var err error
for _, name := range args[1:] {
if !isVarName(name) {
err = fmt.Errorf("unset: `%s': not a valid identifier", sanitize(name))
continue
}
os.Unsetenv(name)
}
return err
case "break", "continue":
return builtinLoopControl(args)
case "alias":
@@ -1776,6 +1861,7 @@ Built-in commands:
quit [code] - Quit shell with status code (default: $?)
set VAR=val - Set environment variable
export VAR=val - Export environment variable
unset VAR - Remove a variable
source file - Run the commands of file in this shell (also: . file)
jobs - List background and stopped jobs
fg [%n] - Continue job n (default: current job) in the foreground
@@ -1808,6 +1894,9 @@ Features:
GOSH_COLORS='user=1;33:path=36' (keys user, root, path, error; values
are ANSI SGR codes, empty = no color); disabled with $NO_COLOR,
TERM=dumb or when output is not a terminal
- Variables: name=value sets a variable (like set), name=value command
sets it only for that command; the value is not split or expanded as
a pattern
- Environment variable expansion ($VAR, ${VAR}, ${VAR:-default});
using an unset variable is an error, use ${VAR:-} for an empty default
- Command substitution: $(command) is replaced by the output of command