This closes PR pkg/25314.
Changes:
* Made various changes to hopefully improve the clarity.
Added COMPATIBILITY, HISTORY, and NOTES sections.
* Made changes to how the shell handles terminating `\' characters
w/ the `-c' and `-t' flags. This is a simple extension of the
same behaviour exhibited when the shell is interactive or when it
executes a command file, the only difference being that where a
terminating `\' character causes the shell to read the next line
of input in an interactive shell or command file, w/ the `-c' and
`-t' flags the shell terminates w/o executing the command line.
* Allow parameter substitution w/ the `-c' and `-t' flags. This
feature is not documented. For example, invoking the shell as
follows allows parameter substitution to take place:
% osh -t one two three
echo $0 $1 $2 $3
-t one two three
* The shell now ignores SIGINT and SIGQUIT when the `-c' or `-t' flag
is used. Thus, asynchronous commands invoked in this way ignore
interrupts as they should.
* Ignore SIGINT and SIGQUIT for all commands started from asynchronous
subshells. For example, `( sleep 300; some_command ) >outfile&' now
ignores `^C' and `^\' as it should.
* Don't ignore SIGINT and SIGQUIT for asynchronous commands started
in command files. If a command file is terminated by one of these
signals, the asynchronous commands should also terminate.
* Reverted a change made to termination reporting in osh-040216 that
was not actually compatible w/ the V6 shell.
* Always terminate the shell when read(2) fails.
This fixes a possible infinite loop.
* Fixed a bug in the parser that caused syntactically incorrect
subshell commands not to be detected as such when preceded by
redirection arguments (e.g., `<infile >outfile ( | )').
This bug was introduced in osh-040216.
* Fixed possible buffer overflows in substparm(); added a new error
message, "Too many characters", and made other changes necessary to
properly deal w/ the new error condition. This problem had been
present since at least osh-020214.
* Made some changes to how globbing is handled by the shell.
Specifically, glob(3) should only be called when an argument contains
unquoted occurrences of any of the glob characters `*', `?', or `['.
Previously, it was being called for every argument of an external
command. This change improves run-time performance slightly as
judged by time(1) and information returned by getrusage(2).
* The above-mentioned change also allows the following compatibility
feature. Added globbing compatibility when the shell is compiled
w/ -DCLONE so that when no matches are found a diagnostic,
"No match", is printed.
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