src/lib/libast/tm/tvsleep.c:
- Since the 'sleep' builtin was backported/fixed from ksh93v- and
ksh2020, it makes sense to use the latest/last tvsleep(3), too.
Looks like this added an interrupt check (errno == EINTR).
Also, new fallback versions for systems without nanosleep(2).
Documentation: src/lib/libast/man/tv.3 (unchanged)
src/lib/libast/features/float:
- libast attempts to determine the binary representation of Inf and
NaN to use as a fall-back code path for systems that do not
support fpclassify(). The libast feature detection did not get
consistent signatures between builds. To fix this, zero the
memory before determining the signature.
src/lib/libast/sfio/sfcvt.c:
- The fall-back code path is broken because there are multiple
representations for NaN - the important thing is to check the
exponent and for a non-zero significand. The trailing bits can be
random or left over from interim operations. For that reason, to
ensure we never end up using the fall-back code path, explicitly
generate a compile error if we end up there.
Based on a patch from @citrus-it:
8bf59a9a8f
but uses POSIX memset(3) instead of deprecated bzero(3).
conf.sh checks for undefined symbols by parsing compiler output and
looking for strings of capital letters and underscores. Modern gcc
produces suggestions for replacement variables too, for example:
error: '_SC_CLOCKRES_MIN' undeclared here (not in a function); did you mean _POSIX_CLOCKRES_MIN?
_SC_CLOCKRES_MIN,
^~~~~~~~~~~~~~~~
_POSIX_CLOCKRES_MIN
This causes good variables to be excluded along with bad, causing differences
between the builtin and system getconf commands.
src/lib/libast/comp/conf.sh:
- Only use lines containing 'error:' and ignore everything starting
from 'did you mean:'. (Note this scripts sets the locale to C.)
Patch from @citrus-it:
061a4b1da1
src/cmd/ksh93/sh/main.c: fixargs():
- Erase the entire length of the command arguments buffer (the
space from argv[0] until environ[0]) so that remnants of longer
command arguments aren't left in 'ps' output when executing a
hashbang-ess script with a shorter command line.
- Disable fixargs() on FreeBSD. It has never had any effect on that
system; apparently it either requires another method to rewrite
arguments for 'ps' output purposes (which?) or it's not possible.
src/cmd/ksh93/tests/basic.sh:
- Skip the test if running on FreeBSD.
This reverts commit 600cb182.
$cc may be a system compiler binary, it is not necessarily a
src/cmd/INIT/cc.* wrapper script; so prefixing 'sh' is wrong.
This upstreams a Solaris patch:
https://github.com/oracle/solaris-userland/blob/master/components/ksh93/patches/050-CR7065478.patch
src/lib/libast/comp/setlocale.c:
- Add wide_wctomb() wrapper for wctomb(3). It changes an invalid
character (wctomb returns -1) to a single byte with length 1.
- set_ctype(): Use wide_wctomb() instead of wctomb(3) as the
conversion discipline function (ast.mb_conv). Effectively this
means there are no invalid characters. Perhaps this is necessary
for compatibility with ASCII. Sadly, no public info available.
This applies a patch from Solaris:
https://github.com/oracle/solaris-userland/blob/master/components/ksh93/patches/160-CR7175995.patch
There is no public information on why it's needed, but it seems
sensible on the face of it. Using a file called '.profile' in the
PWD on login, without a directory path, is redundant at best, since
"$HOME/.profile" (e_profile, see data/msg.c) is already used. And
if the PWD is not $HOME at login time, it seems to me there are
serious problems and the last thing you want is to read some
random and probably dodgy '.profile' from the PWD.
src/cmd/ksh93/sh/init.c: sh_init(): login_files[]:
- Remove redundant/problematic ".profile" entry.
This change was pulled in from:
https://raw.githubusercontent.com/oracle/solaris-userland/master/components/ksh93/patches/185-Bug17714341.patch
No public information about the reasons for this change is
available, but it seems reasonable to trust that the Solaris people
found a legitimate need for it.
src/cmd/ksh93/bltins/cd_pwd.c: b_cd():
- When determining the old PWD before 'cd', do not trust shp->pwd
but get and validate the current PWD using path_pwd().
$KSH_VERSION is initialised as a nameref to ${.sh.version}, but it
was not realiable as it could be overridden from the environment.
Some scripts do version checking so this would allow influencing
their execution.
This fix is inspired by the following Solaris patch:
https://github.com/oracle/solaris-userland/blob/master/components/ksh93/patches/200-17435456.patch
but a different approach was needed, because the code has changed
(see 960a1a99).
src/cmd/ksh93/sh/init.c: env_init():
- Refuse to import $KSH_VERSION. Using strncmp(3) might be crude,
but it's effective and I can't figure out another way.
ksh 93u+ has a subshell leak bug where a variable exported in
function in a subshell is also visible in a different subshell.
This is long fixed in 93u+m, but there wasn't a regression test for
this particular bug yet, so this commit adds one.
This fixes the following bug filed with Solaris: "22964338 ksh93
appears to send SIGHUP to unrelated processes on occasion". It is
fixed by applying this patch by Lijo George from the Solaris repo:
https://github.com/oracle/solaris-userland/blob/master/components/ksh93/patches/260-22964338.patch
The ksh2020 upstream rejected this, but if it's in production use
in Solaris, Solaris, it's probably good enough for 93u+m. If any
breakage is left, it can be fixed later.
https://github.com/att/ast/pull/1
src/cmd/ksh93/include/jobs.h,
src/cmd/ksh93/sh/fault.c,
src/cmd/ksh93/sh/jobs.c:
- Use a new job_hup() function instead of job_kill() to send SIGHUP
to job processes on termination. The new function checks if a job
is in fact still live before issuing SIGHUP to it.
This pulls a new version of sh_iosafefd() from:
https://github.com/oracle/solaris-userland/blob/master/components/ksh93/patches/285-30771135.patch
It was written by Kurtis Rader for ksh2020:
https://github.com/att/ast/issues/198https://github.com/att/ast/pull/199
It is presumably better than the Red Hat version and also comes
with more regression test cases (although it still doesn't fix
modernish BUG_CSUBSTDO, which remains in the TODO file).
This commit does not go along with other peripheral changes from
that patch, i.e. a different name and location of this function.
src/cmd/ksh93/sh/io.c:
- Replace sh_iosafefd() as above.
src/cmd/ksh93/tests/subshell.sh:
- Add and tweak tests from the patch.
This change is pulled from here:
https://github.com/oracle/solaris-userland/blob/master/components/ksh93/patches/280-23332860.patch
Info and reproducers:
https://github.com/att/ast/issues/36
In a -c script (like ksh -c 'commands'), the last command
misredirects standard output if an EXIT or ERR trap is set.
This appears to be a side effect of the optimisation that
runs the last command without forking.
This applies a patch by George Lijo that flags these specific
cases and disables the optimisation.
src/cmd/ksh93/include/defs.h,
src/cmd/ksh93/bltins/trap.c,
src/cmd/ksh93/sh/init.c,
src/cmd/ksh93/sh/main.c,
src/cmd/ksh93/sh/xec.c:
- Apply patch as above.
src/cmd/ksh93/tests/io.sh:
- Add the reproducers from the bug report as regression tests.
This change is pulled from here:
https://github.com/oracle/solaris-userland/blob/master/components/ksh93/patches/275-20855453.patchhttps://github.com/att/ast/issues/30
George Lijo wrote on 17 Feb 2017:
> Here's a reproducible testcase on a Solaris11 host running
> ksh93u+(2012-08-01).
> $ cat a.sh
> #!/bin/sh
>
> AAA="aaa"
> echo 'insert character'
> BBB=`echo ${AAA} | sed "s/aaa/bbb/g"`
> logger "variable BBB = ${BBB}"
>
> $ cat t.sh
> #!/bin/ksh
>
> sleep 10
> /bin/ksh ./a.sh
> exit 0
>
> $
>
> $ ./t.sh
>
> The expected result is:
>
> Apr 9 12:43:34 lab user: [ID 702911 user.notice] variable BBB = bbb
>
> because variable "BBB" is supposed to be set to 'bbb' in a.sh.
>
> But if the parent shell is terminated, the variable is wrongly set.
>
> user@xxxxx$ telnet lab
> ...
> $ ./t.sh & <--- Run t.sh in background.
> [1] 2067
> $ logout <--- CTRL + D to exit while t.sh is running.
> Connection to lab closed by foreign host.
>
> Again, access the system and check the output:
>
> user@xxxxx$ telnet lab
> ...
> $ tail -f /var/adm/messages
> :
> Apr 9 12:47:47 lab user: [ID 702911 user.notice] variable BBB =
> insert character <--- !!!
> Apr 9 12:47:47 lab bbb
> <--- !!!
>
> Thus the variable is wrongly set. (The previous echo string was
> not cleared.)
>
> The issue happens because the EIO error during the logout is not
> handled properly.
src/cmd/ksh93/sh/io.c,
src/lib/libast/include/error.h:
- Amend the ERROR_PIPE() macro to check for EIO as well as EPIPE
and ECONNRESET.
This change is pulled from here:
https://github.com/oracle/solaris-userland/blob/master/components/ksh93/patches/240-22461939.patch
Information:
https://github.com/att/ast/issues/6
George Lijo wrote on 14 Mar 2016:
> I observed this issue in a Solaris 11 system on ksh2012-08-01
> [...]. The issue can be reproduced if we add Asian locales to
> ibus (such as Korean). In the ksh93 shell prompt, input some
> Asian character. ksh promptly dumps core [...].
>
> The coredump happens at the following line no 320 in
> src/cmd/ksh93/edit/emacs.c
> if(c!='\t' && c!=ESC && !isdigit(c)).
>
> I referred the vi.c code and added the digit(c) macro, i.e.
> ((c&~STRIP)==0 && isdigit(c)) and replaced the isdigit(c) usage
> with the "digit(c)" macro.
This change is pulled from here:
https://github.com/oracle/solaris-userland/blob/master/components/ksh93/patches/211-21547336.patch
src/cmd/ksh93/bltins/cd_pwd.c: b_cd():
- The functions path_pwd() and path_relative() in sh/path.c may
return a pointer to e_dot[] (".") as a fallback if they fail to
determine a path. This is a string in read-only memory
(data/msg.c), so must not be freed. A pointer to that string may
end up in sh.pwd (== shp->pwd), so b_cd() needs a check for that.
This change is pulled from here:
https://github.com/oracle/solaris-userland/blob/master/components/ksh93/patches/110-CR7061011.patch
Unfortunately there is no publicly available documentation on why
this change was needed. We just have to assume the Solaris people
knew what they were doing. ksh2020 upstreamed this too (as well as
all the other Solaris patches applied here).
src/cmd/ksh93/sh/nvdisc.c: setdisc():
- If no <event> is known for <np>, return a null pointer instead
of a pointer to the empty string.
The forking fix implemented in 102868f8 and 9d428f8f, which stops
the main shell's hash table from being cleared if PATH is changed
in a subshell, can cause a significant performance penalty for
certain scripts that do something like
( PATH=... command foo )
in a subshell, especially if done repeatedly. This is because the
hash table is cleared (and hence a subshell forks) even for
temporary PATH assignments preceding commands.
It also just plain doesn't work. For instance:
$ hash -r; (ls) >/dev/null; hash
ls=/bin/ls
Simply running an external command in a subshell caches the path in
the hash table that is shared with a main shell. To remedy this, we
would have to fork the subshell before forking any external
command. And that would be an unacceptable performance regression.
Virtual subshells do not need to fork when changing PATH if they
get their own hash tables. This commit adds these. The code for
alias subshell trees (which was removed in ec888867 because they
were broken and unneeded) provided the beginning of a template for
their implementation.
src/cmd/ksh93/sh/subshell.c:
- struct subshell: Add strack pointer to subshell hash table.
- Add sh_subtracktree(): return pointer to subshell hash table.
- sh_subfuntree(): Refactor a bit for legibility.
- sh_subshell(): Add code for cleaning up subshell hash table.
src/cmd/ksh93/sh/name.c:
- nv_putval(): Remove code to fork a subshell upon resetting PATH.
- nv_rehash(): When in a subshell, invalidate a hash table entry
for a subshell by creating the subshell scope if needed, then
giving that entry the NV_NOALIAS attribute to invalidate it.
src/cmd/ksh93/sh/path.c: path_search():
- To set a tracked alias/hash table entry, use sh_subtracktree()
and pass the HASH_NOSCOPE flag to nv_search() so that any new
entries are added to the current subshell table (if any) and do
not influence any parent scopes.
src/cmd/ksh93/bltins/typeset.c: b_alias():
- b_alias(): For hash table entries, use sh_subtracktree() instead
of forking a subshell. Keep forking for normal aliases.
- setall(): To set a tracked alias/hash table entry, pass the
HASH_NOSCOPE flag to nv_search() so that any new entries are
added to the current subshell table (if any) and do not influence
any parent scopes.
src/cmd/ksh93/sh/init.c: put_restricted():
- Update code for clearing the hash table (when changing $PATH) to
use sh_subtracktree().
src/cmd/ksh93/bltins/cd_pwd.c:
- When invalidating path name bindings to relative paths, use the
subshell hash tree if applicable by calling sh_subtracktree().
- rehash(): Call nv_rehash() instead of _nv_unset()ting the hash
table entry; this is needed to work correctly in subshells.
src/cmd/ksh93/tests/leaks.sh:
- Add leak tests for various PATH-related operations in the main
shell and in a virtual subshell.
- Several pre-existing memory leaks are exposed by the new tests
(I've confirmed these in 93u+). The tests are disabled and marked
TODO for now, as these bugs have not yet been fixed.
src/cmd/ksh93/tests/subshell.sh:
- Update.
Resolves: https://github.com/ksh93/ksh/issues/66
The SHOPT_2DMATCH code block in sh_setmatch() modifies the 'ap'
pointer, which is initialised as nv_arrayptr(SH_MATCHNOD). This
caused a (rarely occurring) segfault in the following line near the
end of the function:
ap->nelem -= x;
as this line assumed that 'ap' still had the initial value.
src/cmd/ksh93/sh/init.c: sh_setmatch():
- On init, save ap in ap_save and use ap_save instead of ap where
it should be pointing to SH_MATCHNOD. This also allows removing
two redundant nv_arrayptr(SH_MATCHNOD) calls, slightly increasing
the efficiency of this function.
To ignore binaries generated by 'bin/package flat make', the
entries all need an initial '/' or they will be ignored on deeper
hierarchy levels as well.
Scripts that use floating point shell arithmetic confusingly fail
with 'arithmetic syntax error' when running in a locale that uses
',' as the radix point, because '.' is generally assumed by
scripts. The error message is confounding as the problem is not a
syntax error but a locale that is incompatible with the script.
src/cmd/ksh93/sh/arith.c:
- If the locale's radix point is not '.' but a '.' is found in its
place, issue an informative error message that instructs setting
LC_NUMERIC=C.
Resolves: https://github.com/ksh93/ksh/issues/145
@stephane-chazelas writes:
> Per POSIX[*], cd should skip the $CDPATH processing if the first
> component of the directory given to cd is . or ...
>
> Yet, with ksh93u+m 2021-01-03 at least, while that's OK with ..,
> it's not with . with or without the posix option:
>
> $ CDPATH=/ ./ksh -o posix -c 'cd -P ./etc && pwd'
> /etc
> /etc
>
> It seems to be a regression introduced with ksh93u+ as I can't
> reproduce it with ksh93u or any version prior to that. I can also
> reproduce in u+, v- and the ksh2020 from the Ubuntu 20.04
> package.
src/cmd/ksh93/bltins/cd_pwd.c: b_cd():
- Skip $CDPATH processing not only if the path is absolute, but
also if the initial path component is '.' or '..' (in the latter
case the $CDPATH processing was done but appeared to be a no-op).
src/cmd/ksh93/tests/builtins.sh:
- Add regression test.
[*] https://pubs.opengroup.org/onlinepubs/9699919799.2018edition/utilities/cd.html
Fixes: https://github.com/ksh93/ksh/issues/151
As of this commit, ksh 93u+m has a standard semantic version number
<https://semver.org/>, beginning with 1.0.0-alpha. This is added to
the version string in a way that should be compatible with scripts
parsing ${.sh.version} or $(ksh --version). This addition does not
replace the release date and does not affect $((.sh.version)).
For non-release builds, the version string will be:
FORK/VERSION+HASH YYYY-MM-DD
e.g.: 93u+m/1.0.0-alpha+41ef7f76 2021-01-03
For release builds, it will be:
FORK/VERSION YYYY-MM-DD
e.g.: 93u+m/1.0.0 2021-01-03
It is now automatically decided by bin/package whether to build a
release or development build. When building from a directory that
is not a git repository, or if the current git branch name starts
with a number (e.g. '1.0'), the release build is enabled; otherwise
a development build is the default. This is arranged by adding -D
flags to $CCFLAGS as described below. These flags are prepended to
$CCFLAGS, so they can be overridden by adding your own -D or -U
flags via the environment.
In addition, AST vmalloc is disabled for release builds as of this
commit, forcing the use of the OS's standard malloc(3). In 2021,
this is generally more reliable, faster, and more economical with
memory than AST vmalloc. Several memory leaks and crashing bugs are
avoided, e.g.: <https://github.com/ksh93/ksh/issues/95>.
For development builds, vmalloc stays enabled (along with its known
bugs) because this allows the use of the vmstat builtin, making it
much more efficient to test for memory leaks. For more info, see
the regression test script: src/cmd/ksh93/tests/leaks.sh
bin/package, src/cmd/INIT/package.sh:
- Add flags for build type. In $CCFLAGS, define _AST_ksh_release if
we're not on any git branch or on a git branch whose name starts
with a number. Otherwise, define _AST_git_commit as the first 8
characters of the current git commit hash.
src/lib/libast/features/vmalloc:
- If _AST_ksh_release is defined, disable vmalloc and force use of
the operating system's malloc. Discussion:
https://github.com/ksh93/ksh/issues/95
src/cmd/ksh93/include/version.h:
- Define new format for version string, adding a semantic version
number as well as (for non-release builds) the git commit hash.
src/cmd/ksh93/sh/init.c: e_version[]:
- Add a 'v' to the ${.sh.version} feature string if ksh was
compiled with vmalloc enabled. This allows scripts, such as
regression tests, to detect this.
src/cmd/ksh93/data/builtins.c: sh_optksh[]:
- Add a copyright line crediting the contributors to ksh 93u+m.
Resolves: https://github.com/ksh93/ksh/issues/95
When starting ksh +s, it gets stuck in an infinite loop continually
trying to parse its own binary as a shell script and rejecting it:
$ arch/linux.i386-64/bin/ksh +s
arch/linux.i386-64/bin/ksh: arch/linux.i386-64/bin/ksh: cannot execute [Exec format error]
arch/linux.i386-64/bin/ksh: arch/linux.i386-64/bin/ksh: cannot execute [Exec format error]
arch/linux.i386-64/bin/ksh: arch/linux.i386-64/bin/ksh: cannot execute [Exec format error]
arch/linux.i386-64/bin/ksh: arch/linux.i386-64/bin/ksh: cannot execute [Exec format error]
arch/linux.i386-64/bin/ksh: arch/linux.i386-64/bin/ksh: cannot execute [Exec format error]
[...]
$ echo 'echo "this is stdin"' | arch/linux.i386-64/bin/ksh +s
arch/linux.i386-64/bin/ksh: arch/linux.i386-64/bin/ksh: cannot execute [Exec format error]
(no loop, but still ksh trying to parse itself)
src/cmd/ksh93/sh/init.c: sh_init():
- When forcing on the '-s' option upon finding no command
arguments, also update sh.offoptions, a.k.a. shp->offoptions.
This avoids the inconsistent state causing this problem.
In main.c, there is:
if(sh_isoption(SH_SFLAG))
fdin = 0;
else
(code to open $0 as a file)
This was entering the else block because sh_isoption(SH_SFLAG)
was returning 0, and $0 is set to the ksh binary as it is
supposed to when no other script is provided. When I looked for
why sh_isoption was returning 0, I found main.c's
for(i=0; i<elementsof(shp->offoptions.v); i++)
shp->options.v[i] &= ~shp->offoptions.v[i];
Before this loop, shp->offoptions tracks which options were
explicitly disabled by the user on the command line. The effect
of this loop is to make "explicitly disabled" take precedence
over "implicitly enabled". My patch removes the registration of
the +s option.
Fixes: https://github.com/ksh93/ksh/issues/150
Co-authored-by: Martijn Dekker <martijn@inlv.org>
A recent change in Github's Ubuntu test runners exposed a problem
in the way the all_paths test function replicates 'whence -a'
functionality, causing spurious regression test failures.
The problem occurs when e.g. /bin is a symlink to /usr/bin, but
both are in $PATH. The all_paths function treats them as separate
but 'whence -a' detects a duplicate and will not output /usr/bin/*.
I have not succeeded in making all_paths match 'whence -a' exactly.
src/cmd/ksh93/tests/path.sh: function all_paths:
- Using the -ef test expression operator, remove entries from $PATH
that point to the same directory as another entry in $PATH (e.g.
when /bin is a symlink to /usr/bin but both are in $PATH).
Avoiding such dupes works around the problem.
src/cmd/ksh93/sh/name.c:
- The Empty macro (a constant pointer to the empty string) is already
defined in include/defs.h, so does not need to be repeated here.
GMT and UTC have identical time but are used in different contexts.
When the system time zone is set to GMT (e.g. in the UK at winter
time), the 'printf %T' test could fail as it correctly uses GMT
whereas the test expects UTC.
src/cmd/ksh93/tests/builtins.sh:
- Fix possible false negative in 'printf %T\\n now' test by
replacing GMT with UTC in both 'date' output and 'printf %T'
output, instead of only the former.
Issuing typeset floating point numerics having a precision of 0
failed as the precision/size was being overwritten with the string
length of the value, e.g. 'typeset -F0 x=5.67' would result in
'typeset -F 4 x=5.6700' as len('5.67') is 4.
src/cmd/ksh93/include/nval.h:
- Created a symbolic name of NV_FLTSIZEZERO to respresent a float
having a precision/size of 0. NV_FLTSIZEZERO needs to be a
negative value.
src/cmd/ksh93/bltins/typeset.c:
- In b_typeset(), added code to set tdata.argnum to NV_FLTSIZEZERO
for E, F, X options.
- In setall(), adjusted code to allow for tp->argnum to be negative.
src/cmd/ksh93/sh/name.c: nv_newattr():
- Adjusted option value only change code to handle NV_FLTSIZEZERO as
well as changed to directly setting np->nvsize instead of using
nv_setsize(np,size) as nv_setsize might contain conflicting and/or
redundant code.
- Added missing conditional check of '!(newatts&NV_INTEGER)' to
constrain the size==0 code block to justified strings as
NV_LJUST, NV_RJUST, or NV_ZFILL are only valid for strings if
NV_INTEGER is not set. This code block was mistakenly setting
the precision/size value to the length of the value of an
assignment for floats whereas it should only be performing
auto assignment length for justified strings.
'typeset -xu' and 'typeset -xl' would export the variable but fail
to change case in the value as the check between old and new
attributes did not provide the necesssary insight for lower or
upper case transcoding due to the lower or upper case attribute
being set within typeset.c prior to calling name.c nv_newattr
function.
Previous rhbz#1188377 patch added a conditional check for size==-1
which in effect caused the nv_newattr export code block return
optimization to never be executed as one cannot set any attributes
using the readonly builtin. By altering the size==-1 check to !trans
the export only optimization can run.
Also, the rhbz#1188377 patch altered new_attr function by setting
the new size to oldsize if run by the readonly builtin. The result
of setting size==oldsize allowed the succeeding if statement to
run more frequently and if size was a non-zero value resulted in
nv_setsize resetting the value to what it already was. Investigation
yielded that size was always 0 coming from the readonly builtin.
src/cmd/ksh93/bltins/typeset.c:
- Remove the setting of tdata.argnum to -1 as it is not needed due to
existing name.c nv_newattr() logic.
src/cmd/ksh93/sh/name.c: nv_newattr():
- Corrected the export only check optimization by using !trans instead
of using size==-1.
- Removed previous condition check to set size=oldsize if coming from
the readonly builtin. nv_newattr already had existing logic to
prevent changing the size via nv_setsize as size is always 0 when
coming from readonly builtin.
src/cmd/ksh93/tests/builtins.sh:
- Remove redundant extra bincat=$(whence -p cat).
- Move whence -v/-a tests to path.sh.
- Fix 'whence -q' test so errors are counted outside of a subshell.
src/cmd/ksh93/tests/path.sh:
- Add all_paths function that is basically a reimplementation of
'whence -a -p' in shell. Useful for testing 'whence'.
- Move whence -v/-a tests to here, changing them to use all_paths
where needed. Also fix the 'whence -a' function autoloading
regression test to do the same. This fixes the tests for systems
(such as Slackware) where commands such as 'ls' or 'chmod' have
more than one path in even the default $PATH.
