Yup Shell

Usage

Input model#

First stage Input source
A source command (echo, seq, ls, find, yes, emit) the command generates the stream
A filter with file arguments (cat file.txt, wc -l a.txt) the named files, opened via the framework's ByteFileSource
A filter with no file arguments (grep foo) standard input

Later stages must be filters — a source after a pipe, or file arguments on a non-first stage, are reported as errors. This keeps a pipeline's data flow unambiguous: exactly one place decides where the bytes come from.

Shell expansion#

  • Globbing — unquoted *, ?, and […] expand against the working directory. A pattern with no matches is left literal, matching POSIX default behavior.
  • Tilde — a leading ~ or ~/… expands to the home directory.
  • Quoting — single or double quotes group arguments and suppress expansion (echo '*.go' prints *.go literally).
yup> ls *.go
yup> wc -l *.md
yup> cat ~/notes.txt | grep TODO

Examples#

Sources
yup> echo hello world
yup> seq 1 10
Pipelines
yup> seq 1 10 | grep -v 5 | head -n 3
yup> seq 1 100 | wc -l
yup> echo HELLO | tr A-Z a-z
Files and globs
yup> wc -l *.go
yup> cat data.txt | sort | uniq
Subprocess escape hatches
yup> echo hi | exec cat
yup> echo hello | perl -p 's/l/L/g'

Built-ins#

  • help — list commands and usage
  • version — show version
  • clear — clear the screen
  • exit / quit — leave the shell
  • Lines beginning with # are ignored as comments

Next: Commands for the full catalogue.

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