Computerwelt

The shell

Computerwelt.Emulation.Bash is a bash interpreter written in C#: a lexer, a recursive-descent parser with its own fuel budget, and an evaluator, plus the command implementations a script expects to find.

var bash = Bash.CreateBuilder()
    .WithWorkingDirectory("/home/agent")
    .WithUsername("agent")
    .WithHostname("sandbox")
    .WithEnvironmentVariable("LANG", "C.UTF-8")
    .WithLimits(ExecutionLimits.Strict)
    .Build();

The session keeps state between ExecAsync calls the way a terminal does: the working directory, exported variables, shell functions, aliases and history all persist.

Language support

Everything a script written against POSIX bash normally uses:
Expansion parameter, brace, tilde, arithmetic, command substitution, process substitution, globbing
Quoting single, double, $'…', heredocs and here-strings
Redirection >, >>, <, 2>, &>, >&, file descriptors, pipes
Control flow if, for, while, until, case, select, &&, \|\|, !
Functions definition, arguments, local, return, recursion up to the depth limit
Variables scalars, arrays, associative arrays, ${…} modifiers, declare / readonly / export
Arithmetic $(( … )), let, ((…))
Traps and jobs trap, exit, exit-status semantics

Exit codes are kept exact, because scripts branch on them: 127 is command not found, 126 is not executable, and 2 is a parse or usage error.

Commands

Over a hundred commands ship, all managed implementations:

Group Commands
Navigation and files cd, pwd, ls, tree, stat, file, mkdir, rmdir, rm, cp, mv, ln, touch, chmod, chgrp, truncate, mktemp, readlink, realpath, basename, dirname, du, df
Reading and writing cat, head, tail, tac, rev, nl, tee, wc, od, xxd, strings, column, paste
Searching grep / egrep / fgrep, rg, find, which, type
Transforming sed, awk / gawk / mawk, cut, tr, sort, uniq, comm, shuf, seq, numfmt, printf, echo, diff
Structured data jq, yq
Archives and checksums tar, md5sum, sha1sum, sha256sum and friends
Shell builtins export, local, readonly, unset, set, shopt, alias, unalias, eval, exec, source, ., read, readarray / mapfile, getopts, shift, trap, test / [, true, false, :, let, expr, bc
Process-shaped xargs, timeout, sleep, wait, kill, jobs, command, hash, history, dirs, pushd, popd
Environment env, printenv, date, id, whoami, hostname, uname, compgen

Bash.BuiltinNames enumerates what a given session actually has, which is the authoritative answer after registrations and withholdings are applied.

Process-shaped, not process-backed

kill, jobs and timeout behave the way a script expects, but there are no operating-system processes underneath them. sleep consumes the wall-clock budget like anything else.

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