A virtual jailed shell environment for Go apps backed by an io/fs#FS.
feat(cat): accept -u no-op and surface real errno
Adds POSIX -u (write-without-delay) as a documented no-op
since Go writes are already unbuffered. Replaces hardcoded
"No such file or directory" diagnostics with the real
underlying error so EISDIR/EACCES are reported correctly.
Adds tests for -u, -- terminator with dash-prefixed names,
double-dash stdin consumption, and directory diagnostics.
Refs: docs/posix2018/CONFORMANCE.md
Assisted-by: Claude Opus 4.7 via Claude Code
Signed-off-by: Xe Iaso <me@xeiaso.net>
+43
-4
+6
-3
command/internal/cat/cat.go
+6
-3
command/internal/cat/cat.go
···
37
37
fmt.Fprint(stderr, "Usage: cat [OPTION]... [FILE]...\n")
38
38
fmt.Fprint(stderr, "Concatenate FILE(s) to standard output.\n\n")
39
39
fmt.Fprint(stderr, " -n, --number number all output lines\n")
40
+
fmt.Fprint(stderr, " -u (ignored; Go writes are unbuffered)\n")
40
41
fmt.Fprint(stderr, " --help display this help and exit\n")
41
42
}
42
43
set.SetUsage(usage)
43
44
44
45
number := set.BoolLong("number", 'n', "number all output lines")
46
+
_ = set.Bool('u', "(ignored; Go writes are unbuffered)")
45
47
help := set.BoolLong("help", 0, "display this help and exit")
46
48
47
49
if err := set.Getopt(append([]string{"cat"}, args...), nil); err != nil {
···
91
93
return io.ReadAll(ec.Stdin)
92
94
}
93
95
if ec.FS == nil {
94
-
fmt.Fprintf(stderr, "cat: %s: No such file or directory\n", file)
95
-
return nil, errors.New("no filesystem")
96
+
err := errors.New("no filesystem")
97
+
fmt.Fprintf(stderr, "cat: %s: %s\n", file, err)
98
+
return nil, err
96
99
}
97
100
full := resolvePath(ec, file)
98
101
f, err := ec.FS.Open(full)
99
102
if err != nil {
100
-
fmt.Fprintf(stderr, "cat: %s: No such file or directory\n", file)
103
+
fmt.Fprintf(stderr, "cat: %s: %s\n", file, err)
101
104
return nil, err
102
105
}
103
106
defer f.Close()
+37
-1
command/internal/cat/cat_test.go
+37
-1
command/internal/cat/cat_test.go
···
27
27
write("two.txt", []byte("world\n"))
28
28
write("noeol.txt", []byte("noeol"))
29
29
write("multi.txt", []byte("one\ntwo\nthree\n"))
30
+
write("-file", []byte("dashfile\n"))
31
+
if err := fs.MkdirAll("subdir", 0o755); err != nil {
32
+
t.Fatal(err)
33
+
}
30
34
return fs
31
35
}
32
36
···
122
126
name: "missing file reports error and continues",
123
127
args: []string{"nope.txt", "hello.txt"},
124
128
wantStdout: "hello\n",
125
-
wantErrSub: "No such file or directory",
129
+
wantErrSub: "cat: nope.txt:",
126
130
wantErr: true,
127
131
},
128
132
{
···
131
135
wantStdout: "hello\n",
132
136
},
133
137
{
138
+
name: "double dash allows dash-prefixed filename",
139
+
args: []string{"--", "-file"},
140
+
wantStdout: "dashfile\n",
141
+
},
142
+
{
143
+
name: "u flag accepted as no-op",
144
+
args: []string{"-u", "hello.txt"},
145
+
wantStdout: "hello\n",
146
+
},
147
+
{
148
+
name: "two dashes consume stdin once",
149
+
args: []string{"-", "-"},
150
+
stdin: "foo",
151
+
wantStdout: "foo",
152
+
},
153
+
{
134
154
name: "unknown flag",
135
155
args: []string{"--no-such-flag"},
136
156
wantErr: true,
···
154
174
t.Errorf("stderr = %q, want substring %q", stderr, tt.wantErrSub)
155
175
}
156
176
})
177
+
}
178
+
}
179
+
180
+
func TestCatDirectoryDiagnostic(t *testing.T) {
181
+
stdout, stderr, err := run(t, []string{"subdir"}, "", newFS(t))
182
+
if err == nil {
183
+
t.Fatalf("expected error, got nil; stdout=%q stderr=%q", stdout, stderr)
184
+
}
185
+
if stdout != "" {
186
+
t.Errorf("expected empty stdout, got %q", stdout)
187
+
}
188
+
if !strings.HasPrefix(stderr, "cat: subdir: ") {
189
+
t.Errorf("stderr should start with %q, got %q", "cat: subdir: ", stderr)
190
+
}
191
+
if strings.Contains(stderr, "No such file or directory") {
192
+
t.Errorf("stderr should not hardcode 'No such file or directory'; got %q", stderr)
157
193
}
158
194
}
159
195