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Allow invoking path-bound built-in commands by direct path or preceding PATH assignment (#275)
Path-bound builtins on ksh (such as /opt/ast/bin/cat) break some
basic assumptions about paths in the shell that should hold true,
e.g., that a path output by whence -p or command -v should actually
point to an executable command. This commit should fix the
following:
1. Path-bound built-ins (such as /opt/ast/bin/cat) can now be
executed by invoking the canonical path (independently of the
value of $PATH), so the following will now work as expected:
$ /opt/ast/bin/cat --version
version cat (AT&T Research) 2012-05-31
$ (PATH=/opt/ast/bin:$PATH; "$(whence -p cat)" --version)
version cat (AT&T Research) 2012-05-31
In the event an external command by that path exists, the
path-bound builtin will now override it when invoked using the
canonical path. To invoke a possible external command at that
path, you can still use a non-canonical path, e.g.:
/opt//ast/bin/cat or /opt/ast/./bin/cat
2. Path-bound built-ins will now also be found on a PATH set
locally using an assignment preceding the command, so something
like the following will now work as expected:
$ PATH=/opt/ast/bin cat --version
version cat (AT&T Research) 2012-05-31
The builtin is not found by sh_exec() because the search for
builtins happens long before invocation-local preceding
assignments are processsed. This only happens in sh_ntfork(),
before forking, or in sh_fork(), after forking. Both sh_ntfork()
and sh_fork() call path_spawn() to do the actual path search, so
a check there will cover both cases.
This does mean the builtin will be run in the forked child if
sh_fork() is used (which is the case on interactive shells with
job.jobcontrol set, or always after compiling with SHOPT_SPAWN
disabled). Searching for it before forking would mean
fundamentally redesigning that function to be basically like
sh_ntfork(), so this is hard to avoid.
src/cmd/ksh93/sh/path.c: path_spawn():
- Before doing anything else, check if the passed path appears in
the builtins tree as a pathbound builtin. If so, run it. Since a
builtin will only be found if a preceding PATH assignment
temporarily changed the PATH, and that assignment is currently in
effect, we can just sh_run() the builtin so a nested sh_exec()
invocation will find and run it.
- If 'spawn' is not set (i.e. we must return), set errno to 0 and
return -2. See the change to sh_ntfork() below.
src/cmd/ksh93/sh/xec.c:
- sh_exec(): When searching for built-ins and the restricted option
isn't active, also search bltin_tree for names beginning with a
slash.
- sh_ntfork(): Only throw an error if the PID value returned is
exactly -1. This allows path_spawn() to return -2 after running a
built-in to tell sh_ntfork() to do the right things to restore
state.
src/cmd/ksh93/sh/parse.c: simple():
- When searching for built-ins at parse time, only exclude names
containing a slash if the restricted option is active. This
allows finding pointers to built-ins invoked by literal path like
/opt/ast/bin/cat, as long as that does not result from an
expansion. This is not actually necessary as sh_exec() will also
cover this case, but it is an optimisation.
src/lib/libcmd/getconf.c:
- Replace convoluted deferral to external command by a simple
invocation of the path to the native getconf command determined
at compile time (by src/lib/libast/comp/conf.sh). Based on:
https://github.com/ksh93/ksh/issues/138#issuecomment-816384871
If there is ever a system that has /opt/ast/bin/getconf as its
default native external 'getconf', then there would still be an
infinite recursion crash, but this seems extremely unlikely.
Resolves: https://github.com/ksh93/ksh/issues/138
This commit is contained in:
Martijn Dekker
GitHub
parent
2c38fb93fd
commit
519bb08265
10 changed files with 82 additions and 144 deletions
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@ -31,8 +31,8 @@ static const char usage[] =
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"[--catalog?" ERROR_CATALOG "]"
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"[+NAME?date - set/list/convert dates]"
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"[+DESCRIPTION?\bdate\b sets the current date and time (with appropriate"
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" privilege), lists the current date or file dates, or converts"
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" dates.]"
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" privileges, provided the shell isn't in restricted mode), lists"
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" the current date or file dates, or converts dates.]"
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"[+?Most common \adate\a forms are recognized, including those for"
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" \bcrontab\b(1), \bls\b(1), \btouch\b(1), and the default"
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" output from \bdate\b itself.]"
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@ -27,7 +27,7 @@
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*/
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static const char usage[] =
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"[-?\n@(#)$Id: getconf (AT&T Research) 2012-06-25 $\n]"
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"[-?\n@(#)$Id: getconf (ksh 93u+m) 2021-04-09 $\n]"
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"[--catalog?" ERROR_CATALOG "]"
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"[+NAME?getconf - get configuration values]"
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"[+DESCRIPTION?\bgetconf\b displays the system configuration value for"
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@ -53,11 +53,11 @@ static const char usage[] =
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" Only one of \b--call\b, \b--name\b or \b--standard\b may be specified.]"
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"[+?This implementation uses the \bastgetconf\b(3) string interface to the native"
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" \bsysconf\b(2), \bconfstr\b(2), \bpathconf\b(2), and \bsysinfo\b(2)"
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" system calls. If \bgetconf\b on \b$PATH\b is not the default native"
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" \bgetconf\b, named by \b$(getconf GETCONF)\b, then \bastgetconf\b(3)"
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" checks only \bast\b specific extensions and the native system calls;"
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" invalid options and/or names not supported by \bastgetconf\b(3) cause"
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" the \bgetconf\b on \b$PATH\b to be executed.]"
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" system calls."
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" Invalid options and/or names not supported by \bastgetconf\b(3) cause"
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" the default native \bgetconf\b, named by \b$(getconf GETCONF)\b, to"
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" be executed (unless the shell is in restricted mode, in which case"
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" an error will occur).]"
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"[a:all?Call the native \bgetconf\b(1) with option \b-a\b.]"
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"[b:base?List base variable name sans call and standard prefixes.]"
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@ -137,25 +137,12 @@ b_getconf(int argc, char** argv, Shbltin_t* context)
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register char* path;
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register char* value;
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register const char* s;
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register const char* t;
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char* pattern;
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char* native;
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char* cmd;
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Path_t* e;
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Path_t* p;
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int flags;
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int n;
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int i;
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int m;
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int q;
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char** oargv;
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char buf[PATH_MAX];
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Path_t std[64];
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struct stat st0;
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struct stat st1;
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static const char empty[] = "-";
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static const Path_t equiv[] = { { "/bin", 4 }, { "/usr/bin", 8 } };
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cmdinit(argc, argv, context, ERROR_CATALOG, 0);
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oargv = argv;
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@ -288,121 +275,11 @@ b_getconf(int argc, char** argv, Shbltin_t* context)
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return error_info.errors != 0;
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defer:
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/*
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* defer to argv[0] if absolute and it exists
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* Run the external getconf command
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*/
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if ((cmd = oargv[0]) && *cmd == '/' && !access(cmd, X_OK))
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goto found;
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/*
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* defer to the first getconf on $PATH that is also on the standard PATH
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*/
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e = std;
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s = astconf("PATH", NiL, NiL);
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q = !stat(equiv[0].path, &st0) && !stat(equiv[1].path, &st1) && st0.st_ino == st1.st_ino && st0.st_dev == st1.st_dev;
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m = 0;
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do
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{
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for (t = s; *s && *s != ':'; s++);
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if ((n = s - t) && *t == '/')
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{
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if (q)
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for (i = 0; i < 2; i++)
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if (n == equiv[i].len && !strncmp(t, equiv[i].path, n))
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{
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if (m & (i+1))
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t = 0;
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else
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{
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m |= (i+1);
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if (!(m & (!i+1)))
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{
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m |= (!i+1);
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e->path = t;
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e->len = n;
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e++;
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if (e >= &std[elementsof(std)])
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break;
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t = equiv[!i].path;
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n = equiv[!i].len;
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}
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}
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}
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if (t)
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{
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e->path = t;
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e->len = n;
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e++;
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}
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}
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while (*s == ':')
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s++;
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} while (*s && e < &std[elementsof(std)]);
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if (e < &std[elementsof(std)])
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{
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e->len = strlen(e->path = "/usr/sbin");
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if (++e < &std[elementsof(std)])
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{
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e->len = strlen(e->path = "/sbin");
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e++;
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}
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}
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if (s = getenv("PATH"))
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do
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{
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for (t = s; *s && *s != ':'; s++);
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if ((n = s - t) && *t == '/')
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{
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for (p = std; p < e; p++)
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if (p->len == n && !strncmp(t, p->path, n))
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{
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sfsprintf(buf, sizeof(buf), "%-*.*s/%s", n, n, t, error_info.id);
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if (!access(buf, X_OK))
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{
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cmd = buf;
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goto found;
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}
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}
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}
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while (*s == ':')
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s++;
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} while (*s);
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/*
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* defer to the first getconf on the standard PATH
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*/
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for (p = std; p < e; p++)
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{
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sfsprintf(buf, sizeof(buf), "%-*.*s/%s", p->len, p->len, p->path, error_info.id);
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if (!access(buf, X_OK))
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{
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cmd = buf;
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goto found;
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}
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}
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/*
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* out of deferrals
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*/
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if (name)
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error(4, "%s: unknown name -- no native getconf(1) to defer to", name);
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else
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error(4, "no native getconf(1) to defer to");
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return 2;
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found:
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/*
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* don't blame us for crappy diagnostics
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*/
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oargv[0] = cmd;
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oargv[0] = native;
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if ((n = sh_run(context, argc, oargv)) >= EXIT_NOEXEC)
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error(ERROR_SYSTEM|2, "%s: exec error [%d]", cmd, n);
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error(ERROR_SYSTEM|2, "%s: exec error [%d]", native, n);
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return n;
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}
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@ -37,7 +37,8 @@ static const char usage[] =
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" separated, on a single line. When more than one option is specified"
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" the output is in the order specified by the \b-A\b option below."
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" Unsupported option values are listed as \a[option]]\a. If any unknown"
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" options are specified, the OS default \buname\b(1) is called.]"
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" options are specified, the OS default \buname\b(1) is called (unless"
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" the shell is in restricted mode, in which case an error will occur).]"
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"[+?If any \aname\a operands are specified then the \bsysinfo\b(2) values"
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" for each \aname\a are listed, separated by space, on one line."
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" \bgetconf\b(1), a pre-existing \astandard\a interface, provides"
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