Implementing POSIX.1-2024

[magicant]

This issue tracks the tasks involved in implementing the requirements for the shell as defined by The Open Group Base Specifications Issue 8.

• Do not exit on an exec error in an interactive shell exec: Don't exit on exec failure if interactive #87
• Update $! when resuming a background job #88
• Allow esac as the first pattern of a case branch #89
• ;& in case command ;&, ;|, and ;;& in case command items #90
• Dollar-single-quotes
• Declaration utility #20
• New printf built-in semantics
  • Support indexing (%n$) in the printf built-in
  • Reject redundant characters after a quote for a numeric value operand
• New cd built-in semantics
  • Update the exit status of cd where the new PWD value cannot be determined (with and without -e)
  • Reject an empty operand in the cd built-in
• Update the exit status of getopts on error
• New trap built-in semantics
  • trap (without options or operands) should show signals ignored by inheritance in exec
  • trap -p (without operands) should show all signals
• New read built-in semantics (except byte-wise field splitting)
  • Add the -d option to the read built-in
  • The read built-in should treat quotes and escapes as specified in POSIX.1-2024
  • Return from the read built-in different exit statuses depending on the result
• New job control semantics
  • Report immediately on suspension of a foreground job
  • Save the terminal state on suspension of a foreground job and restore when resuming
  • Treat a job suspended when any of its component processes is suspended
  • Treat successive synchronous and-or lists as a single foreground job
  • Discard remaining part of the current list when a foreground process is suspended
  • Allow job control without a controlling terminal
    • Avoid allocating a controlling terminal if the shell does not already have one
  • Use SIGTTIN to suspend the shell when starting job control in the background
  • Reset the shell’s process group ID to match the process ID when starting job control
• Accept -- separator in the exec built-in
• Reject if a redirection operand expands to more than one field in an interactive shell *
• Abort the current line and continue the next when an interactive shell encounters a shell error that would exit a non-interactive shell
• Exclude . and .. from pathname expansion results
• Change false, pwd, and true to substitutive built-ins
• Enable the interactive mode if the shell is invoked with the -s option and an operand with stdin and stderr connected to a terminal
• Disallow disabling the ulimit built-in in configure and add test cases for the built-in
• Remove a trailing slash from tilde expansion replacement
• Reject parentheses and the -a and -o options in the test built-in in the POSIXly-correct mode
• Reject making LINENO, OLDPWD, OPTARG, OPTIND, and PWD readonly *
• Document POSIX non-conformance of brace expansion
• Return exit status 128 on unrecoverable read error
• Set the exit status of suspended jobs to $? only in interactive job-controlling shells
• Report the process (group) ID when an interactive shell starts a background job
• Signal the shell process when the shell is exiting with an exit status representing a signal
• Support (or reject) {n} prefix of redirections
• Keep the tilde expansion result with an empty HOME from empty field removal
• Reconsider the semantics of the -h and -o nolog options and update documentation
• Reconsider when alias substitution should be performed in command substitutions of the form $(...)
• Import only variables that have a valid name from the environment
• Allow any non-null bytes (possibly not valid characters) in environment variable values
• Allow any non-null bytes (possibly not valid characters) in parameter values
• Change result types of expansions from character strings to bytes
• Reimplement field splitting in terms of bytes
• Revise field splitting in the read built-in to match the new field splitting semantics
• Sort byte-by-byte if results of pathname expansion collate equal
• Update documentation on the POSIX version

Items marked with an asterisk are behaviors that are newly allowed (but not required) by POSIX.1-2024.

The following are requirements that were not added in POSIX.1-2024, but have existed since earlier versions of POSIX.

• exit-p.tst: default exit status in signal trap
• return-p.tst: default exit status in function in trap
• return-p.tst: default exit status in trap in function
• Remove temporary file on termination signal #81
• Non-interactive shell should not ignore stop signals #26