Implementing shell language semantics (POSIX portability)

[magicant]

This is a tracking issue for implementation of the portable part of the shell language semantics.
For yash-specific semantics, see #260.

• Read-eval loop #102
• Word expansion
  • Literal character 783986c e1f2cba
  • Backslashes c4fe703 74aa07c
  • Single-quotes 19575fb e1f2cba
  • Double-quotes Expanding double-quotes #74 0c6c06c
  • Tilde expansion semantics (POSIX portability) #190
  • Parameter expansion
    • Scalar variable expansion Basic parameter expansion semantics #79 79db2e9
    • Special parameter expansion
      • ?, ! Expand special parameters $? and $! #95 79db2e9
      • @, * Expanding positional parameters $@ and $* #145
      • # d90ea11
      • - 0943934
      • $ b96602c 79db2e9
      • 0 83d54d9
    • Length modifier 2333324
    • Switch modifier semantics (POSIX portability) #197
    • Trim modifiers #202
  • Command substitution Command substitution semantics #103 6f8d1a6
  • Arithmetic expansion semantics (POSIX portability) #169
  • Field splitting (and empty field removal) #156
  • Globbing (pathname expansion) #158
  • Quote removal & attribute stripping 031f694 Split attribute stripping out of quote removal #142
• Command execution
  • List 84b96c6 35742dc
  • Executing and-or list #78
  • Executing pipelines #62
  • Executing asynchronous command #92
  • Executing simple command #80
  • Compound commands
    • Braces ({ foo; }) 4b06934
    • Subshell semantics #166 ((foo))
    • Loops
      • For loop semantics #167
      • Semantics of while/until loop #168
      • Break built-in #188
      • Continue built-in #189
    • Executing case command #184
    • If conditional construct d2d5d7e
    • Redirections fb9d2a6
  • Executing function definition #76
• Redirections
  • File redirections #87 (<, >, >|, >>, <>)
  • File descriptor duplications #194 (<&, >&)
  • Here-document semantics #195 (<<, <<-)
• Consequences of shell errors #204
• Implementing semantics about traps #109
• Properties of special built-in utilities
  • See Executing simple command #80 and Consequences of shell errors #204

[magicant]

So, what should we start with? 🤔

• List
  • A method to test side effects
    • (Simulated) standard output
    • The echo built-in, or a fake of it
  • A method to test exit status
    • Exit status in Env
    • A fake built-in that returns an arbitrary exit status
• More on simple command
  • Assignment
    • Variables in Env
  • Command search
    • Functions in Env
    • $PATH
      • Variables in Env
    • A (simulated) method to test whether a file is executable
  • Executing external commands
    • Creating subshells in Env
    • Performing exec in Env
• Basic part of word expansion
  • Type of word expansion functions
  • Variables in Env