Strands Shell commands

Strands Shell reimplements a curated subset of POSIX and coreutils in Rust, targeting the operations agents reach for most rather than a complete toolset. This page is the reference for what is supported and where behavior diverges from GNU or BSD: missing flags, unsupported features, and known gaps.

This page covers the external commands the shell reimplements. They group into text processing, file contents, file management, path and system utilities, networking, JSON, and search. The shell language and builtins have their own page, Shell language and builtins; lua is covered in Lua scripting.

General callouts

These notes apply across commands:

Regex uses the Rust regex crate. Backreferences and lookaround are unavailable, so grep -P is unsupported and GNU BRE escapes are not translated.
jq is backed by jaq, a jq subset.
Unsupported flags are rejected, not ignored. Idioms like cp -p, set -o pipefail, or ln -sf produce an error rather than succeeding with incorrect behavior.
Multiple file arguments are not uniformly supported. cut and uniq read only the first file; head and tail return a hard error; cat, sort, and wc handle multiple files correctly.
Malformed numeric input passes silently. test, [, and arithmetic $(( )) treat non-numeric or empty operands as 0 without an error.
Stdin under strands-shell -c is not connected to commands (bad fd 0). Use an in-shell pipe instead.

Text processing

Command	Notable gaps
`grep`	No `-P`, backreferences, lookaround, or `-f`. `-o` on empty-matching patterns emits blank lines.
`sed`	No branching (`b`, `t`, `:label`) or multiline (`N`, `D`, `P`); no `-f`. `s///N` replaces the incorrect match; range `c` emits per line.
`tr`	Missing `[:punct:]`, `[:cntrl:]`, and `[c*n]` repeats. `-c` two-set translate uses the incorrect replacement character.
`cut`	No `-b` or `--complement`. Reads only the first file when given several.
`sort`	No `-c`, `-o`, `-V`, or `-h` (`-h` incorrectly prints help). Keyed-tie order is non-deterministic. Loads all input into memory.
`uniq`	No `-w` or `-D`. Reads only the first file when given several.
`wc`	No `-m` (char count) or `-L`. Counts are correct; column padding differs from coreutils.

File contents

Command	Notable gaps
`cat`	No `-b`, `-s`, `-A`, `-e`, or `-t`; no `-` stdin operand.
`head`	No `-c`, negative `-n`, or `head -5` shorthand. Multiple files produce a hard error (no `==>` headers).
`tail`	No `-c`, `-f` or `-F` follow, or shorthand. Multiple files produce a hard error.
`tee`	No `-i`. Standard usage (stdout plus files, `-a`) is supported.

File management

Command	Notable gaps
`cp`	`-r` works, including nested directories; no `-p`, `-a`, `-f`, or `-i`. `cp f f` silently succeeds.
`mv`	Rename, move, and cross-mount operations work; no `-f`, `-i`, `-n`, or `-v`.
`rm`	`-r`, `-f`, and symlink non-follow behave correctly; no `-d` or `-i`.
`mkdir`	No `-m`. An invalid-option path returns exit 0.
`rmdir`	No `-p`.
`touch`	File creation and timestamp update only; no `-t`, `-d`, `-c`, or `-r` (cannot set a specific time).
`ln`	`-s` only; hard links are refused by design; no `-f`, so `ln -sf` fails.
`chmod`	Full support. Octal and symbolic modes; no `-R`.

Path and system

Command	Notable gaps
`ls`	`-l` omits owner, group, and link count; `-a` omits `.` and `..`. No `-t`, `-S`, `-d`, `-F`, or `-h`. Output is always single-column.
`basename`	No `-a` or `-s`. `basename /` and `""` diverge from coreutils.
`dirname`	Single operand only. A trailing slash is mishandled (`/usr/lib/` becomes `/usr/lib`).
`readlink`	Plain read only; no `-f`, `-e`, or `-m` canonicalization.
`mktemp`	No `-u` or `-t`.
`date`	`%s` is not expanded; unknown specifiers pass through literally; no `-d` or `-r`. UTC only.
`env`	Print-only. `env VAR=v cmd`, `-i`, and `-u` are not supported; use the shell-prefix form instead.
`echo`	Expands escapes by default; `-e` and `-E` are printed literally (escape expansion cannot be disabled).
`pwd`	Full support, including `-L` and `-P`.
`sleep`	No unit suffixes (`0.1s`). Respects the shell timeout.
`true`, `false`	Full support.

Networking

Command	Notable gaps
`curl`	GET, POST, JSON, headers, auth, redirects, and `-w` are supported. No `--max-time`, `--connect-timeout`, or `--retry` (risk of an indefinite hang); no `-I`, `-F`, `-A`, `-G`, or cookie jar. SSRF and credential controls are enforced.

The SSRF guard and credential injection on curl are security features, covered in the security model. They are not optional and cannot be disabled per command.

JSON

Command	Notable gaps
`jq` (jaq)	Broad filter coverage. A missing nested key throws an error, which breaks the `.a.b // default` pattern; no `--arg`, `--argjson`, or `-S`; `inputs` and `setpath` are absent.

Search

Command	Notable gaps
`find`	`-name`, `-type`, `-maxdepth`, `-exec`, and `-print0` are supported. No `-delete`, `-size`, `-mtime`, `-prune`, or `-regex`. Children are sorted alphabetically, not in readdir order.
`xargs`	Space-separated `-n`, `-I`, `-0`, and `-d` are supported; attached forms (`-n1`, `-I{}`) and `-t`, `-r`, `-L`, `-P` are not. Implicitly behaves as `-r`.

Scripting and shell language

lua runs a sandboxed Lua 5.4 interpreter for logic that would otherwise sprawl across a chain of pipes: multi-step transforms, structured-data manipulation, or calling nested MCP servers as Lua modules. See Lua scripting.

The shell language itself (pipelines, redirections, conditionals, loops, functions, and expansions) and the builtins (test, printf, read, set, and the rest) are documented in Shell language and builtins.