u_long. Before this change it was of type int for syscalls, but prototypes
in sys/stat.h and documentation for chflags(2) and fchflags(2) (but not
for lchflags(2)) stated that it was u_long. Now some related functions
use u_long type for flags (strtofflags(3), fflagstostr(3)).
- Make path argument of type 'const char *' for consistency.
Discussed on: arch
Sponsored by: The FreeBSD Foundation
If syntactically invalid job identifiers are to be taken as jobs that exited
with status 127, this should not apply to options, so that we can add
options later if need be.
This ensures 'return' in a trap returns the correct status to the caller.
If evalskip is not set or if it is overridden by a previous evalskip, keep
the old behaviour of restoring the exit status from before the trap.
access, birth, change and modify times of two files, instead of only
being able to compare modify times. The builtin test in sh(1) will
automagically acquire the same expansion.
Approved by: grog
MFC after: 2 weeks
If a stack mark is set while the current stack block is empty, the stack
block may move later on (because of realloc()) and the stack mark needs to
be updated. This updating does not happen after popstackmark() has been
called; therefore, call setstackmark() again if the stack mark is still
being used.
For some reason, this only affects a few users. I cannot reproduce it. The
situation seems quite rare as well because an empty stack block would
usually be freed (by popstackmark()) before execution reaches a
setstackmark() call.
PR: 175922
Tested by: KT Sin
Now it outputs fixed files, which use constants provided by the C standard
library to determine appropriate values for the target machine.
Before, mksyntax inspected the host machine which resulted in subtle
breakage if e.g. char is signed on the host and unsigned on the target such
as when cross-compiling on x86 for ARM.
Tested using -funsigned-char on amd64. Compiling build-tools without it and
sh itself with it causes various tests to fail without this change but not
with this change. With consistent -funsigned-char, tests pass with or
without this change.
The mksyntax program could be removed and syntax.c and syntax.h committed to
the repository.
Submitted by: Christoph Mallon
MFC after: 2 weeks
ISO/IEC 9899:1999 (E) 5.2.1p3 guarantees that the values of the characters
0123456789 are contiguous.
The generated syntax.c and syntax.h remain the same.
Submitted by: Christoph Mallon
Expand here documents at the same point other redirections are expanded but
use a non-fork subshell environment (like simple command substitutions) for
compatibility. Substitition errors result in an empty here document like
before.
As a result, a fork is avoided for short (<4K) expanded here documents.
Unexpanded here documents (with quoted end marker after <<) are not affected
by this change. They already only forked when >4K.
Side effects:
* Order of expansion is slightly different.
* Slow expansions are not executed in parallel with the redirected command.
* A non-fork subshell environment is subtly different from a forked process.
set an exclusive advisory lock on stdout. This will be used to guarantee
orderly writing to METALOG.
Sponsored by: DARPA, AFRL
Obtained from: NetBSD (mason)
Otherwise with '-v' we print out the file name as if it was copied:
/tmp/2gb-card/M0132.CTG not overwritten
/mnt/DCIM/CANONMSC/M0132.CTG -> /tmp/2gb-card/M0132.CTG
If a loop contained certain commands (such as redirected compound commands),
the temporary memory for the redirection was not freed between iterations of
the loop but only after the loop.
Put a stackmark in evaltree(), freeing memory whenever a node has been
evaluated. Some other stackmarks are then redundant; remove them.
Example:
while :; do { :; } </dev/null; done
command name of a thread from a multi-threaded process that doesn't have
an available argument list (such as kernel processes) and threads display
is enabled via -H.
Reviewed by: alfred, delphij, eric@vangyzen.net
MFC after: 1 week
Instead of rechecking relative paths for all hashed utilities after a cd,
track if any utility in cmdtable depends on a relative path in PATH.
If there is such a utility, cd clears the entire table.
As a result, the '*' in hash no longer happens.
Accessing sys_siglist directly requires rtld to copy it from libc to the sh
executable's BSS. Also, strsignal() will put in the signal number for
unknown signals (FreeBSD-specific) so we need not do that ourselves.
Unfortunately, there is no function for sys_signame.
If there is a write error on stdout, a message will be printed (to stderr)
and the exit status will be changed to 2 if it would have been 0 or 1.
PR: bin/158206
if (exists AND (NOT f_option) AND
((not_writable AND input_is_terminal) OR i_option))
prompt
in particular, add the test for input_is_terminal
PR: bin/173039
Submitted by: Mark Johnston <markjdb@gmail.com>
Approved by: cperciva
MFC after: 3 days
* The last character is not displayed.
* If the alias ends with itself (as a word), an infinite memory-eating loop
occurs.
If an alias is defined initially, a space is appended to avoid recursion but
this did not happen when an alias was later modified.
PR: bin/173418
Submitted by: Daniel F.
MFC after: 1 week
sorting order for time and name with the -t option. IEEE Std 1003.2
(POSIX.2) mandates that the -t option sort in descending order, and
that if two files have the same timestamp, they should be sorted in
ascending order of their names. The -r flag reverses both of these
sort orders, so they're never the same. This creates significant
problems for sequentially named files stored on FAT file systems,
where it can be impossible to list them in the order in which they
were created.
Add , (comma) option to print file sizes grouped and separated by
thousands using the non-monetary separator returned by localeconv(3),
typically a comma or period.
MFC after: 14 days
Although sufficient memory is available for a longer string in cmdname,
this is undefined behaviour anyway.
Side effect: for alignment reasons, an additional byte of memory is
allocated per hashed command.
In addition to adding missing `static' keywords:
- bin/dd: Pull in `extern.h' to guarantee consistency with source file.
- libexec/rpc.rusersd: Move shared globals into an extern.h.
- libexec/talkd: Move `debug' and `hostname' into extern.h.
- usr.bin/cksum: Put counters in extern.h, as they are used by ckdist/mtree.
- usr.bin/m4: Move `end_result' into extern.h.
- usr.sbin/services_mkdb: Move shared globals into an extern.h.
In addition to adding `static' where possible:
- bin/date: Move `retval' into extern.h to make it visible to date.c.
- bin/ed: Move globally used variables into ed.h.
- sbin/camcontrol: Move `verbose' into camcontrol.h and fix shadow warnings.
- usr.bin/calendar: Remove unneeded variables.
- usr.bin/chat: Make `line' local instead of global.
- usr.bin/elfdump: Comment out unneeded function.
- usr.bin/rlogin: Use _Noreturn instead of __dead2.
- usr.bin/tset: Pull `Ospeed' into extern.h.
- usr.sbin/mfiutil: Put global variables in mfiutil.h.
- usr.sbin/pkg: Remove unused `os_corres'.
- usr.sbin/quotaon, usr.sbin/repquota: Remove unused `qfname'.
This self-written compiler warning, which is hopefully going to be
committed into LLVM sources soon, warns about potentially missing
`static' keywords, similar to -Wmissing-prototypes.
- bin/pax: Move external declaration of chdname and s_mask into extern.h.
- bin/setfacl: Move setfacl.c-specific stuff out of setfacl.h.
- sbin/mount_fusefs: Remove char *progname; use getprogname().
- others: add `static' where possible.
This reduces code duplication and code size.
/usr/bin/printf is not affected.
Side effect: different error messages when certain builtins are passed
invalid options.
help tools understand that we're not leaking it.
PR: bin/171634
Submitted by: Erik Cederstrand <erik@cederstrand.dk>
Approved by: cperciva
MFC after: 3 days
# setfacl -m u:trasz:rwx x
# setfacl -m u:root:rwx x
# getfacl x
# file: x
# owner: root
# group: wheel
user::rw-
user:root:rwx
user:trasz:rwx
group::r--
mask::rwx
other::r--
# setfacl -m u:root:rwx x
setfacl: x: acl_calc_mask() failed: Invalid argument
setfacl: x: failed to set ACL mask
For NFSv4 ACLs, this sort of situation would result in duplicated
entries.
MFC after: 1 month
PR submitter suggested adding it to acl(3) instead, but I don't think
pointing ordinary users at section 3 is a good idea.
PR: docs/162380
MFC after: 1 month
This structure is not part of POSIX. According to POSIX, gettimeofday()
has the following prototype:
int gettimeofday(struct timeval *restrict tp, void *restrict tzp);
Also, POSIX states that gettimeofday() shall return 0 (as long as tzp is
not used). Remove dead error handling code. Also use NULL for a
nul-pointer instead of integer 0.
While there, change all pieces of code that only use tv_sec to use
time(3), as this provides less overhead.
symbolic link to a directory for the target as a symbolic link instead of
a directory. This makes it possible to atomically update a symbolic
link using rename().
Reviewed by: gj
MFC after: 2 weeks
When waiting for child processes using "wait" or if "set -T" is in effect, a
signal interrupts the wait. Make sure there is no window where the signal
handler may be invoked (setting a flag) just before going to sleep.
There is a similar race condition in the shell language, but scripts can
avoid it by exiting from the trap handler or enforcing synchronization using
a fifo.
If SIGCHLD is not trapped, a signal handler must be installed for it. Only
install this handler for the duration of the wait to avoid triggering
unexpected [EINTR] errors elsewhere.
Note that for some reason only SIGINT and SIGQUIT interrupt a "wait"
command. This remains the case.
Examples:
export x=~
now expands the tilde
local y=$1
is now safe, even if $1 contains IFS characters or metacharacters.
For a word to "look like an assignment", it must start with a name followed
by an equals sign, none of which may be quoted.
The special treatment applies when the first word (potentially after
"command") is "export", "readonly" or "local". There may be quoting
characters but no expansions. If "local" is overridden with a function there
is no special treatment ("export" and "readonly" cannot be overridden with a
function).
If things like
local arr=(1 2 3)
are ever allowed in the future, they cannot call a "local" function. This
would either be a run-time error or it would call the builtin.
This matches Austin Group bug #351, planned for the next issue of POSIX.1.
PR: bin/166771
On recent versions of NetBSD's libedit, el_gets
now sets el_len to -1 on error so we can
distinguish between a NULL string and an error.
This fixes sh from exiting with newer versions
of libedit now allowing EINTR to return.
Obtained from: NetBSD
Reviewed by: jilles
MFC after: 3 weeks
directory entry then use the struct stat from that instead of doing
it again, and skip the rm_overwrite() call if fts_read() indicated
that the entry couldn't be a regular file.
Obtained from: OpenBSD
MFC after: 1 week
that the file we have opened is the one we expected. Also open in
non-blocking mode to avoid a potential hang with FIFOs.
Obtained from: NetBSD via OpenBSD
1. Avoid a cd back into ${.CURDIR} to run mkbuiltins when we know make
will first cd into ${.OBJDIR}. Keep the cwd to what make sets it to.
2. Don't tell mkbuiltins where to write to (= ${.OBJDIR}), but where to
get sources from (= ${.CURDIR}). This to compensate for point 1.
This fixes a problem with bmake's mk files that optimize ${.OBJDIR} to
expand to "." after changing cwd, not taking into account that the
target is pretty much undoing that and not getting the full path to the
object tree anymore.
scripts the way sysctl(8) is. The -N option, like in sysctl(8),
displays only the kenv names, not their values. The -v option prints an
individual kenv variable name with its value as name="value". This is
the inverse of sysctl(8)'s -n flag, since the default behaviour of
kenv(1) is already like sysctl(8) -n.
Submitted by: Garrett Cooper < yanegomi AT gmail DOT com >
MFC after: 1 week
quotation. Also make sure we have the same amount of columns in each row as
the number of columns we specify in the head arguments.
Reviewed by: brueffer
This uses vfork() for simple commands and command substitutions containing a
single simple command, invoking an external program under certain conditions
(no redirections or variable assignments, non-interactive shell, no job
control). These restrictions limit the amount of code executed in a vforked
child.
There is a large speedup (for example 35%) in microbenchmarks. The
difference in buildkernel is smaller (for example 0.5%) but still
statistically significant. See
http://lists.freebsd.org/pipermail/freebsd-hackers/2012-January/037581.html
for some numbers.
The use of vfork() can be disabled by setting a variable named
SH_DISABLE_VFORK.
In the first command of a 'for', $? should be the exit status of the last
pipeline (command substitution in the word list or command before 'for'),
not always 0.
Before this fix, only the first statement of the trap was executed if
evalskip was set. This is for example the case when:
o "-e" is set for this shell
o a trap is set on EXIT
o a function returns 1 and causes the script to abort
Reviewed by: jilles
MFC after: 2 weeks
Also, rework evalcase() to not evaluate any tree. Instead, return the
NCLISTFALLTHRU node and handle it in evaltree().
Fixed bugs:
* If a ;& list with non-zero exit status is followed by an empty ;; or final
list, the exit status of the case command should be equal to the exit
status of the ;& list, not 0.
* An empty ;& case should not reset $?.
* If no pattern is matched, POSIX says the exit status shall be 0 (even if
there are command substitutions).
* If a pattern is matched and there are no command substitutions, the first
command should see the $? from before the case command, not always 0.
The errno message display added in r222292 did not take attempting to
cd to a non-directory or something that cannot be stat()ed into account.
PR: bin/164070
MFC after: 10 days
This improves performance for globs where a slash or another component
follows a component with metacharacters by eliminating unnecessary attempts
to open directories that are not.
This is not necessary: errors are already caught in evalbackcmd() and
forcelocal handles changes to variables.
Note that this depends on r223024.
MFC after: 4 weeks
Free expanded case text before executing commands.
Remove impossible evalskip checks (expanding an argument cannot set
evalskip anymore since $(break) and the like are properly executed in a
subshell environment).
For these simple utilities, it doesn't harm to make all global variables
static. In fact, this allows the compiler to perform better forms of
optimisation and analysis.
display() to calculate column widths, but was not initialized in
main(). This resulted in a division by zero.
Noticed by: Michael Butler <imb@protected-networks.net>
- In the argc == 0 case, just populate the mount list as before, but
do not calculate widths, update totals or print anything.
- In the argv > 0 case, collect information about the requested file
systems and store it in the mount list, but do not calculate
widths, update totals or print anything.
- In either case, once all the information has been collected,
iterate once through the mount list to calculate widths and totals,
then once more to print everything.
This also fixes two bugs: firstly, column widths were not calculated
correctly if more than one file system was specified on the command
line; and secondly, file systems with MNT_IGNORE were included in the
totals even if -a was not specified.
Noticed by: Paul Schenkeveld
MFC after: 3 weeks
- there's no reason the semantics of the -x flag are being explained in
the -a flag description
- be more precise regarding the relation between the -a flag and the
security.bsd.see_other_uids sysctl
- describe the format of the -t flag's argument
- 'con' no longer is a possible entry in the 'TT' column
- explain that the 'TT' column refers to pseudo-terminals via mere numbers
- add a hint in the 'tt' keyword description that a keyword 'tty' exists,
which will give the full terminal pathname
Submitted by: arundel (via docs@) (original)
MFC after: 1 week
With-MFC: 225908
As of FreeBSD 6, devices can only be opened through devfs. These device
nodes don't have major and minor numbers anymore. The st_rdev field in
struct stat is simply based a copy of st_ino.
Simply display device numbers as hexadecimal, using "%#jx". This is
allowed by POSIX, since it explicitly states things like the following
(example taken from ls(1)):
"If the file is a character special or block special file, the
size of the file may be replaced with implementation-defined
information associated with the device in question."
This makes the output of these commands more compact. For example, ls(1)
now uses approximately four columns less. While there, simplify the
column length calculation from ls(1) by calling snprintf() with a NULL
buffer.
Don't be afraid; if needed one can still obtain individual major/minor
numbers using stat(1).
Because sh executes commands in subshell environments without forking in
more and more cases (particularly from 8.0 on), it makes sense to describe
subshell environments more precisely using ideas from POSIX, together with
some FreeBSD-specific items.
In particular, the hash and times builtins may not behave as if their state
is copied for a subshell environment while leaving the parent shell
environment unchanged.
to re-establishment of 64bit arithmetic, but is committed separately, to
not obscure that conversion. This commit does not change the observed
behaviour of expr in any way. Style will be fixed in a follow-up commit.
again. This brings back the behaviour of expr in FreeBSD-4, which had been
reverted due to an assumed incompatbility with POSIX.1 for FreeBSD-5.
This issue has been discussed in the freebsd-standards list, and the
consensus was, that POSIX.1 is in fact not violated by this extension,
since it affects only cases of POSIX undefined behaviour (overflow of
signed long).
Other operating systems did upgrade their versions of expr to support
64bit range, after it had been initially brought to FreeBSD. They have
used it for a decade without problems, meanwhile.
The -e option is retained, but it will only select less strict checking
of numeric parameters (leading white-space, leading "+" are allowed and
skipped, an empty string is considered to represent 0 in numeric context.)
The call of check_utility_compat() as a means of establishing backwards
compatibility with FreeBSD-4 is considered obsolete, but preserved in
this commit. It is expected to be removed in a later revision of this
file.
Reviewed by: bde, das, jilles
MFC after: 2 month (those parts that do not violate POLA)
* Shell patterns are also for ${var#pat} and the like.
* An '!' by itself will not trigger pathname generation so do not call it a
meta-character, even though it has a special meaning directly after an
'['.
* Character ranges are locale-dependent.
* A '^' will complement a character class like '!' but is non-standard.
MFC after: 1 week
POSIX requires a -h option to sh and set, to locate and remember utilities
invoked by functions as they are defined. Given that this
locate-and-remember process is optional elsewhere, it seems safe enough to
make this option do nothing.
POSIX does not specify a long name for this option. Follow ksh in calling it
"trackall".
Replacing ;; with the new control operator ;& will cause the next list to be
executed as well without checking its pattern, continuing until a list ends
with ;; or until the end of the case statement. This is like omitting
"break" in a C "switch" statement.
The sequence ;& was formerly invalid.
This feature is proposed for the next POSIX issue in Austin Group issue
#449.
The eval special builtin now runs the code with EV_EXIT if it was run
with EV_EXIT itself.
In particular, this eliminates one fork when a command substitution contains
an eval command that ends with an external program or a subshell.
This is similar to what r220978 did for functions.
Have mkbuiltins write the prototypes for the *cmd functions to builtins.h
instead of builtins.c and include builtins.h in more .c files instead of
duplicating prototypes for *cmd functions in other headers.
In optimized command substitution, save and restore any variables changed by
expansions (${var=value} and $((var=assigned))), instead of trying to
determine if an expansion may cause such changes.
If $! is referenced in optimized command substitution, do not cause jobs to
be remembered longer.
This fixes $(jobs $!) again, simplifies the man page and shortens the code.
When I added UTF-8 support in r221646, the LC_COLLATE-based ordering broke
because of sign extension of char.
Because of libc restrictions, this does not work for UTF-8. For UTF-8
locales, ranges always use character code order.
In most cases, login shells are started from the home directory, but not in
all, such as xterm -ls.
This commit depends on r222957 for read_profile() performing parameter
expansion.
PR: bin/50569
The function name expandstr() and the general idea of doing this kind of
expansion by treating the text as a here document without end marker is from
dash.
All variants of parameter expansion and arithmetic expansion also work (the
latter is not required by POSIX but it does not take extra code and many
other shells also allow it).
Command substitution is prevented because I think it causes too much code to
be re-entered (for example creating an unbounded recursion of trace lines).
Unfortunately, our LINENO is somewhat crude, otherwise PS4='$LINENO+ ' would
be quite useful.
The "exp" builtin is undocumented, non-standard and not very useful.
If exp's return value is not used, something like
VAR=$(exp EXPRESSION)
is equivalent to
VAR=$((EXPRESSION))
except that errors in the expression are fatal and quoting special
characters is not needed in the latter case.
If exp's return value is used, something like
if exp EXPRESSION >/dev/null
can be replaced by
if [ $((EXPRESSION)) -ne 0 ]
with similar differences.
The exp-run showed that "let" is close enough to bash's and ksh's builtin
that removing it would break a few ports. Therefore, "let" remains in 9.x.
PR: bin/104432
Exp-run done by: pav (with some other sh(1) changes)
CDPATH should be ignored not only for pathnames starting with '/' but also
for pathnames whose first component is '.' or '..'.
The man page already describes this behaviour.
If IFS is null, unquoted $@/$* should still expand to separate words.
This differs from quoted $@ (which does not depend on IFS) in that pathname
generation is performed and empty words are removed.
If the length of a directory in PATH together with the given filename
exceeded FILENAME_MAX (which may happen even for pathnames that work), a
static buffer was overflown.
The static buffer is unnecessary, we can use the stalloc() stack.
Obtained from: NetBSD
MFC after: 1 week
This reflects failure to determine the pathname of the new directory in the
exit status (1). Normally, cd returns successfully if it did chdir() and the
call was successful.
In POSIX, -e only has meaning with -P; because our -L is not entirely
compliant and may fall back to -P mode, -e has some effect with -L as well.
This is sometimes used with eval or old-style command substitution, and most
shells other than ash derivatives allow it.
It can also be used with scripts that violate POSIX's requirement on the
application that they end in a newline (scripts must be text files except
that line length is unlimited).
Example:
v=`cat <<EOF
foo
EOF`
echo $v
This commit does not add support for the similar construct with new-style
command substitution, like
v=$(cat <<EOF
foo
EOF)
This continues to require a newline after the terminator.
Because we have no iconv in base, support for other charsets is not
possible.
Note that \u/\U are processed using the locale that was active when the
shell started. This is necessary to avoid behaviour that depends on the
parse/execute split (for example when placing braces around an entire
script). Therefore, UTF-8 encoding is implemented manually.
?, [...] patterns match codepoints instead of bytes. They do not match
invalid sequences. [...] patterns must not contain invalid sequences
otherwise they will not match anything. This is so that ${var#?} removes the
first codepoint, not the first byte, without putting UTF-8 knowledge into
the ${var#pattern} code. However, * continues to match any string and an
invalid sequence matches an identical invalid sequence. (This differs from
fnmatch(3).)
This ensures that mbrtowc(3) can be used directly once it has been verified
that there is no CTL* byte. Dealing with a CTLESC byte within a multibyte
character would be complicated.
The new values do occur in iso-8859-* encodings. This decreases efficiency
slightly but should not affect correctness.
Caveat: Updating across this change and rebuilding without cleaning may
yield a subtly broken sh binary. By default, make buildworld will clean and
avoid problems.
A string between $' and ' may contain backslash escape sequences similar to
the ones in a C string constant (except that a single-quote must be escaped
and a double-quote need not be). Details are in the sh(1) man page.
This construct is useful to include unprintable characters, tabs and
newlines in strings; while this can be done with a command substitution
containing a printf command, that needs ugly workarounds if the result is to
end with a newline as command substitution removes all trailing newlines.
The construct may also be useful in future to describe unprintable
characters without needing to write those characters themselves in 'set -x',
'export -p' and the like.
The implementation attempts to comply to the proposal for the next issue of
the POSIX specification. Because this construct is not in POSIX.1-2008,
using it in scripts intended to be portable is unwise.
Matching the minimal locale support in the rest of sh, the \u and \U
sequences are currently not useful.
Exp-run done by: pav (with some other sh(1) changes)
Note that this only applies to variables that are actually used.
Things like (0 && unsetvar) do not cause an error.
Exp-run done by: pav (with some other sh(1) changes)
In particular, this makes things like ${#foo[0]} and ${#foo[@]} errors
rather than silent equivalents of ${#foo}.
PR: bin/151720
Submitted by: Mark Johnston
Exp-run done by: pav (with some other sh(1) changes)
For backgrounded pipelines and subshells, the previous value of $? was being
preserved, which is incorrect.
For backgrounded simple commands containing a command substitution, the
status of the last command substitution was returned instead of 0.
If fork() fails, this is an error.
If the -p option is turned off, privileges from a setuid or setgid binary
are dropped. Make sure to check if this succeeds. If it fails, this is an
error which will cause the shell to abort except in interactive mode or if
'command' was used to make 'set' or an outer 'eval' or '.' non-special.
Note that taking advantage of this feature and writing setuid shell scripts
seems unwise.
MFC after: 1 week
If EV_EXIT causes an exit, use the exception mechanism to unwind
redirections and local variables. This way, if the final command is a
redirected command, an EXIT trap now executes without the redirections.
Because of these changes, EV_EXIT can now be inherited by the body of a
function, so do so. This means that a function no longer prevents a fork
before an exec being skipped, such as in
f() { head -1 /etc/passwd; }; echo $(f)
Wrapping a single builtin in a function may still cause an otherwise
unnecessary fork with command substitution, however.
An exit command or -e failure still invokes the EXIT trap with the
original redirections and local variables in place.
Note: this depends on SHELLPROC being gone. A SHELLPROC depended on
keeping the redirections and local variables and only cleaning up the
state to restore them.
This is only a problem if IFS contains digits, which is unusual but valid.
Because of an incorrect fix for PR bin/12137, "${#parameter}" was treated
as ${#parameter}. The underlying problem was that "${#parameter}"
erroneously added CTLESC bytes before determining the length. This
was properly fixed for PR bin/56147 but the incorrect fix was not backed
out.
Reported by: Seeker on forums.freebsd.org
MFC after: 2 weeks
POSIX does not require the shell to fork for a subshell environment, and we
use that possibility in various ways (command substitutions with a single
command and most subshells that are the final command of a shell process).
Therefore do not tie subshells to forking in the man page.
Command substitutions with expansions are a bit strange, causing a fork for
$(...$(($x))...) because $x might expand to y=2; they will probably be
changed later but this is how they work now.
These already worked: $# ${#} ${##} ${#-} ${#?}
These now work as well: ${#+word} ${#-word} ${##word} ${#%word}
There is an ambiguity in the standard with ${#?}: it could be the length of
$? or it could be $# giving an error in the (impossible) case that it is not
set. We continue to use the former interpretation as it seems more useful.
