aboutsummaryrefslogtreecommitdiff
path: root/toys
diff options
context:
space:
mode:
Diffstat (limited to 'toys')
-rw-r--r--toys/pending/sh.c544
1 files changed, 364 insertions, 180 deletions
diff --git a/toys/pending/sh.c b/toys/pending/sh.c
index 9f686932..7436ada2 100644
--- a/toys/pending/sh.c
+++ b/toys/pending/sh.c
@@ -8,7 +8,7 @@
*
* The first link describes the following shell builtins:
*
- * break colon continue dot eval exec exit export readonly return set shift
+ * break : continue dot eval exec exit export readonly return set shift
* times trap unset
*
* The second link (the utilities directory) also contains specs for the
@@ -25,9 +25,9 @@
* TODO: Handle embedded NUL bytes in the command line? (When/how?)
* TODO: replace getenv() with faster func: sort env and binary search
- * buitins: alias bg command fc fg getopts jobs newgrp read umask unalias wait
- * disown umask suspend source pushd popd dirs logout times trap
- * unset local export readonly set : . let history declare
+ * builtins: alias bg command fc fg getopts jobs newgrp read umask unalias wait
+ * disown umask suspend source pushd popd dirs logout times trap
+ * unset local export readonly set : . let history declare
* "special" builtins: break continue eval exec return shift
* builtins with extra shell behavior: kill pwd time test
@@ -121,10 +121,13 @@ GLOBALS(
struct sh_process {
struct sh_process *next, *prev;
struct arg_list *delete; // expanded strings
- int *urd, envlen, pid, exit; // undo redirects, child PID, exit status
+ // undo redirects, a=b at start, child PID, exit status, has !
+ int *urd, envlen, pid, exit, not;
struct sh_arg arg;
} *procs, *proc;
} *jobs, *job;
+
+ struct sh_arg *arg;
)
#define BUGBUG 0
@@ -216,27 +219,35 @@ static char *getvar(char *s)
return getvarlen(s, strlen(s));
}
-// returns offset of next unquoted (or double quoted if dquot) char.
-// handles \ '' "" `` $()
-int skip_quote(char *s, int dquot, int *depth)
+// TODO: make parse_word use this?
+// returns length of current quote context. Handles \ '' "" `` $()
+int skip_quote(char *s)
{
- int i, q = dquot ? *depth : 0;
+ int i, q = 0;
// quotes were checked for balance and overflow by parse_word()
for (i = 0; s[i]; i++) {
char c = s[i], qq = q ? toybuf[q-1] : 0;
- if (c == '\\') i++;
- else if (dquot && q==1 && qq=='"' && c!='"') break;
- else if (qq!='\'' && c=='$' && s[1]=='(') {
+ // backslash escapes skip a char, and return for EOL or unquoted.
+ if (c == '\\') {
+ if (qq!= '\'' && qq!='`') {
+ if (!s[++i]) return i;
+ if (!q) return ++i;
+ }
+ // $( triggers anywhere but inside ' '
+ } else if (qq!='\'' && c=='$' && s[1]=='(') {
toybuf[q++] = ')';
- i++;
- } else if (q && qq==c) q--;
+ i+=2;
+ // unquoted parentheses nest inside $(), I.E. "$(()" isn't done yet.
+ } else if (c=='(' && qq==')') toybuf[q++] = ')';
+ // end current quoting context with match
+ else if (q && qq==c) q--;
+ // start new non-nesting quoting context only at top level
else if ((!q || qq==')') && (c=='"' || c=='\'' || c=='`')) toybuf[q++] = c;
- else if (!q) break;
- }
- if (dquot) *depth = q;
+ if (!q) break;
+ }
return i;
}
@@ -253,6 +264,213 @@ void add_arg(struct arg_list **list, char *arg)
*list = al;
}
+// Return next available high (>=10) file descriptor
+int next_hfd()
+{
+ int hfd;
+
+ for (; TT.hfd<=99999; TT.hfd++) if (-1 == fcntl(TT.hfd, F_GETFL)) break;
+ hfd = TT.hfd;
+ if (TT.hfd > 99999) {
+ hfd = -1;
+ if (!errno) errno = EMFILE;
+ }
+
+ return hfd;
+}
+
+// Perform a redirect, saving displaced filehandle to a high (>10) fd
+// rd is an int array: [0] = count, followed by from/to pairs to restore later.
+// If from == -1 just save to, else dup from->to after saving to.
+int save_redirect(int **rd, int from, int to)
+{
+ int cnt, hfd, *rr;
+
+ // save displaced to, copying to high (>=10) file descriptor to undo later
+ // except if we're saving to environment variable instead (don't undo that)
+ if ((hfd = next_hfd())==-1) return 1;
+ if (hfd != dup2(to, hfd)) hfd = -1;
+ else fcntl(hfd, F_SETFD, FD_CLOEXEC);
+
+if (BUGBUG) dprintf(255, "%d redir from=%d to=%d hfd=%d\n", getpid(), from, to, hfd);
+ // dup "to"
+ if (from != -1 && to != dup2(from, to)) {
+ if (hfd != -1) close(hfd);
+
+ return 1;
+ }
+
+ // Append undo information to redirect list so we can restore saved hfd later.
+ if (!((cnt = *rd ? **rd : 0)&31)) *rd = xrealloc(*rd, (cnt+33)*2*sizeof(int));
+ *(rr = *rd) = ++cnt;
+ rr[2*cnt-1] = hfd;
+ rr[2*cnt] = to;
+
+ return 0;
+}
+
+// TODO: waitpid(WNOHANG) to clean up zombies and catch background& ending
+static void subshell_callback(void)
+{
+ TT.subshell_env = xmprintf("@%d,%d=", getpid(), getppid());
+ xsetenv(TT.subshell_env, 0);
+ TT.subshell_env[strlen(TT.subshell_env)-1] = 0;
+}
+
+// TODO check every caller of run_subshell for error, or syntax_error() here
+// from pipe() failure
+
+// TODO eliminate prototypes
+static int sh_run(char *new);
+static void unredirect(int *urd);
+
+
+// Pass environment and command string to child shell, return PID of child
+static int run_subshell(char *str, int len)
+{
+ pid_t pid;
+
+ // The with-mmu path is significantly faster.
+ if (CFG_TOYBOX_FORK) {
+ char *s;
+
+ if ((pid = fork())<0) perror_msg("fork");
+ else if (!pid) {
+ s = xstrndup(str, len);
+ sh_run(s);
+ free(s);
+
+ _exit(toys.exitval);
+ }
+
+ // On nommu vfork, exec /proc/self/exe, and pipe state data to ourselves.
+ } else {
+ int pipes[2], i;
+
+ // open pipe to child
+ if (pipe(pipes) || 254 != dup2(pipes[0], 254)) return 1;
+ close(pipes[0]);
+ fcntl(pipes[1], F_SETFD, FD_CLOEXEC);
+
+ // vfork child
+ pid = xpopen_setup(0, 0, subshell_callback);
+
+ // marshall data to child
+ close(254);
+ if (TT.locals)
+ for (i = 0; TT.locals[i]; i++) dprintf(pipes[1], "%s\n", TT.locals[i]);
+ dprintf(pipes[1], "%.*s\n", len, str);
+ close(pipes[1]);
+ }
+
+ return pid;
+}
+
+// Call subshell with either stdin/stdout redirected, return other end of pipe
+int pipe_subshell(char *s, int len, int out)
+{
+ int pipes[2], *uu = 0, in = !out;
+
+ // Grab subshell data
+ if (pipe(pipes)) {
+ perror_msg("%.*s", len, s);
+
+ return -1;
+ }
+
+ // Perform input or output redirect and launch process
+ save_redirect(&uu, pipes[in], in);
+ close(pipes[in]);
+ run_subshell(s, len); // ignore errors, don't track
+ unredirect(uu);
+
+ return pipes[out];
+}
+
+// utf8 strchr: return wide char matched at wc from chrs, or 0 if not matched
+// if len, save length of wc when matched
+static int utf8chr(char *wc, char *chrs, int *len)
+{
+ wchar_t wc1, wc2;
+ int ll;
+
+ if (!*wc) return 0;
+
+ ll = utf8towc(&wc1, wc, 99);
+ if (ll<0 || wc1<1) {
+ if (len) ++*len;
+ return *wc;
+ }
+ if (wc1 > 0) {
+ if (len) *len = ll;
+ while (*(chrs += utf8towc(&wc2, chrs, 99))) if (wc1 == wc2) break;
+ if (*chrs) return wc1;
+ }
+
+ return 0;
+}
+
+// find utf8 characters in utf string
+// if c return first char in chrs or null terminator (ala strcspn)
+// else return first char not in chars (ala strspn)
+static char *utf8spnc(char *str, char *chrs, int c)
+{
+ int ll, len;
+
+ while (*str) {
+ ll = utf8chr(str, chrs, &len);
+ if (c ? ll : !ll) break;
+ str += len;
+ }
+
+ return str;
+}
+
+
+// This reeeeeally wants to be inline because we marshall half the function's
+// state to it and it write _back_ to more than one. End of loop?
+
+// Perform word splitting via $IFS, adding split chunks
+// Returns newly allocated end chunk.
+// input *off is length of new, output *off = resolved length
+static char *split_add(struct sh_arg *arg, struct arg_list **delete,
+ char *before, char *new, char *after, char quote, int *off)
+{
+// TODO TT.ifs
+ char *ifs = getenv("IFS"), *end = new;
+ int i, j, len;
+
+ if (!ifs) ifs = " \t\n";
+
+ if (!(quote&1)) while (*new && *(end = utf8spnc(new, ifs, 1))) {
+ new = xmprintf("%.*s%.*s", *off, before, (int)(end-new), new);
+ *off = 0;
+ for (j = 0; (i = utf8chr(end, ifs, &len)); end += len) {
+
+ // runs of space allowed/collapsed before and after non-whitespace IFS
+ if (!(j&1)) {
+ if (iswspace(i)) {
+ if (!j && new && !*new && !quote) {
+ free(new);
+ new = 0;
+ }
+ } else if (++j == 3) break;
+ } else j++;
+ }
+ if (new) {
+ add_arg(delete, new);
+ array_add(&arg->v, arg->c++, new);
+ quote = 0;
+ }
+ new = end;
+ }
+
+ end = xmprintf("%.*s%s%s", *off, before, new, after);
+ *off += strlen(new);
+
+ return end;
+}
+
#define NO_PATH (1<<0) // path expansion (wildcards)
#define NO_SPLIT (1<<1) // word splitting
#define NO_BRACE (1<<2) // {brace,expansion}
@@ -264,96 +482,158 @@ void add_arg(struct arg_list **list, char *arg)
// TODO: ${name:?error} causes an error/abort here (syntax_err longjmp?)
// TODO: $1 $@ $* need args marshalled down here: function+structure?
// arg = append to this
-// new = string to expand
+// str = string to expand
// flags = type of expansions (not) to do
// delete = append new allocations to this so they can be freed later
// TODO: at_args: $1 $2 $3 $* $@
-static void expand_arg_nobrace(struct sh_arg *arg, char *old, unsigned flags,
+static void expand_arg_nobrace(struct sh_arg *arg, char *str, unsigned flags,
struct arg_list **delete)
{
- char *new = old, *s, *ss, *sss;
+ char cc, qq = 0, *old = str, *new = str, *s, *ss;
+ int ii = 0, jj, kk, oo;
if (flags&FORCE_KEEP) old = 0;
// TODO ls -l /proc/$$/fd
// Tilde expansion
- if (!(flags&NO_TILDE) && *new == '~') {
+ if (!(flags&NO_TILDE) && *str == '~') {
struct passwd *pw = 0;
// first expansion so don't need to free previous new
ss = 0;
- for (s = new; *s && *s!=':' && *s!='/'; s++);
- if (s-new==1) {
+ while (str[ii] && str[ii]!=':' && str[ii]!='/') s++;
+ if (ii==1) {
if (!(ss = getvar("HOME")) || !*ss) pw = bufgetpwuid(getuid());
} else {
// TODO bufgetpwnam
- pw = getpwnam(sss = xstrndup(new+1, (s-new)-1));
- free(sss);
+ pw = getpwnam(s = xstrndup(str+1, ii-1));
+ free(s);
}
if (pw && pw->pw_dir) ss = pw->pw_dir;
if (!ss || !*ss) ss = "/";
- s = xmprintf("%s%s", ss, s);
+ s = xmprintf("%s%s", ss, str+ii);
if (old != new) free(new);
new = s;
}
- // parameter/variable expansion
+ // parameter/variable expansion, and dequoting
-// TODO this is wrong
- if (*new == '$') {
- char *s = getvar(new+1);
+ for (oo = 0; (cc = str[ii++]); old != new && (new[oo] = 0)) {
+ // skip literal chars
+ if (!strchr("$'`\\\"", cc)) {
+ if (old != new) new[oo++] = cc;
+ continue;
+ }
- if (new != old) free(new);
- if (!s) return;
- new = xstrdup(s);
- }
+ // allocate snapshot if we just started modifying
+ if (old == new) {
+ new = xstrdup(new);
+ new[oo = ii-1] = 0;
+ }
-/*
- for (s = new; *(s += skip_quote(s, 1, &depth));) {
- if (*s == '`') {
+ // handle different types of escapes
+ if (cc == '\\') new[oo++] = str[ii] ? str[ii++] : cc;
+ else if (cc == '"') qq++;
+ else if (cc == '\'') {
+ if (qq&1) new[oo++] = cc;
+ else {
+ qq += 2;
+ while ((cc = str[ii++]) != '\'') new[oo++] = cc;
+ }
+ // both types of subshell work the same, so do $( here not in '$' below
+// TODO $((echo hello) | cat) ala $(( becomes $( ( retroactively
+ } else if (cc == '`' || (cc == '$' && str[ii] == '(' && str[ii+1] != '(')) {
+ kk = skip_quote(str+ii);
+ jj = cc == '$';
+// TODO what does \ in `` mean? What is echo `printf %s \$x` supposed to do?
+ jj = pipe_subshell(str+ii+1+jj, kk-2-jj, 1);
+ ii += kk;
+ ss = readfd(jj, 0, 0);
+ close(jj);
+ if (ss && *ss) {
+ kk = strlen(ss);
+ while (kk && ss[kk-1]=='\n') ss[--kk] = 0;
+
+ s = split_add(arg, delete, new, ss, str+ii, qq, &oo);
+ if (new != old) free(new);
+ new = s;
+ }
+ // Blank subshells don't add an argument.
+ if (!str[ii]) {
+ if (new != old) free(new);
+ new = 0;
+ }
+ } else if (cc == '$') {
+ char buf[16];
+ s = buf;
+
+// *@#?-$!_0 "Special Paremeters" ($0 not affected by shift)
+
+
+ if (!(cc = str[ii++])) {
+ new[oo++] = cc;
+ break;
+ } else if (cc == '?') {
+ char buf[16];
+ sprintf(buf, "%d", toys.exitval);
+
+ s = split_add(arg, delete, new, buf, str+ii, qq, &oo);
+ if (new != old) free(new);
+ new = s;
+ } else if (cc == '*' || cc == '@') {
+ // Quoted agglomeration
+ if ((qq&1) && cc=='*') {
+ for (jj = kk = 0; jj<TT.arg->c; jj++) kk += strlen(TT.arg->v[jj]);
+ s = xmalloc(oo+kk+TT.arg->c+strlen(str+ii)+1);
+ memcpy(s, new, oo);
+ for (jj = 0; jj<TT.arg->c; jj++)
+ oo += sprintf(s+oo, " %s"+!jj, TT.arg->v[jj]);
+ strcpy(s+oo, str+ii);
+ } else for (jj = 0; jj<TT.arg->c; jj++) {
+ s = split_add(arg, delete, new, TT.arg->v[jj],
+ jj+1==TT.arg->c ? str+ii : "", qq, &oo);
+ if (new != old) free(new);
+ new = s;
+ }
+ } else if(isdigit(cc)) {
+ for (kk = 0, ii--; isdigit(cc = str[ii]); ii++) kk = (10*kk)+cc-'0';
+ s = split_add(arg, delete, new, kk<TT.arg->c ? TT.arg->v[kk] : "",
+ str+ii, qq, &oo);
+ if (new != old) free(new);
+ new = s;
-// ${ $(( $( $[ $' ` " '
+ // TODO: ${ $(( $( $[ $'
+// } else if (cc == '{') {
- while (*s) {
- if (quote != '*s == '$') {
- // *@#?-$!_0 "Special Paremeters" ($0 not affected by shift)
- // 0-9 positional parameters
- if (s[1] == '$'
+ } else {
+ s = str+--ii;
+ for (jj = 0; s[jj] && (s[jj]=='_' || !ispunct(s[jj])); jj++);
+ s = jj ? getvarlen(str+ii, jj) : 0;
+ s = xstrdup(s ? s : "");
+ ii += jj;
+ s = split_add(arg, delete, new, s, str+ii, qq, &oo);
+ if (new != old) free(new);
+ new = s;
+ }
}
}
- // replacement
- while (*s) {
- if (*s == '$') {
- s++;
- } else if (*strchr("*?[{", *s)) {
- s++;
- } else if (*s == '<' || *s == '>') {
- s++;
- } else s++;
- }
-*/
+// TODO globbing * ? [
-// TODO not else?
- // quote removal
- else if (!(flags&NO_QUOTE)) {
- int to = 0, from = 0;
+// Word splitting completely eliminating argument when no non-$IFS data left
+// wordexp keeps pattern when no matches
- for (;;) {
- char c = new[from++];
+// TODO NO_SPLIT cares about IFS, see also trailing \n
- if (c == '"' || c=='\'') continue;
- if (c == '\\' && new[from]) c = new[from++];
- if (from != to && old == new) new = xstrdup(new);
- if (!(new[to++] = c)) break;
- }
- }
+// quote removal
// Record result.
- if (old==new && (flags&FORCE_COPY)) new = xstrdup(new);
- if (old!=new) add_arg(delete, new);
- array_add(&arg->v, arg->c++, new);
+ if (*new || qq) {
+ if (old==new && (flags&FORCE_COPY)) new = xstrdup(new);
+ if (old!=new) add_arg(delete, new);
+ array_add(&arg->v, arg->c++, new);
+ } else if(old != new) free(new);
}
// expand braces (ala {a,b,c}) and call expand_arg_nobrace() each permutation
@@ -369,7 +649,7 @@ static void expand_arg(struct sh_arg *arg, char *old, unsigned flags,
// collect brace spans
if (!(flags&NO_BRACE)) for (i = 0; ; i++) {
- i += skip_quote(old+i, 0, 0);
+ while ((j = skip_quote(old+i))) i += j;
if (!bb && !old[i]) break;
if (bb && (!old[i] || old[i] == '}')) {
bb->active = bb->commas[bb->cnt+1] = i;
@@ -552,51 +832,6 @@ if (BUGBUG) dprintf(255, "urd %d %d\n", rr[0], rr[1]);
free(urd);
}
-// Return next available high (>=10) file descriptor
-int next_hfd()
-{
- int hfd;
-
- for (; TT.hfd<=99999; TT.hfd++) if (-1 == fcntl(TT.hfd, F_GETFL)) break;
- hfd = TT.hfd;
- if (TT.hfd > 99999) {
- hfd = -1;
- if (!errno) errno = EMFILE;
- }
-
- return hfd;
-}
-
-// Perform a redirect, saving displaced filehandle to a high (>10) fd
-// rd is an int array: [0] = count, followed by from/to pairs to restore later.
-// If from == -1 just save to, else dup from->to after saving to.
-int save_redirect(int **rd, int from, int to)
-{
- int cnt, hfd, *rr;
-
- // save displaced to, copying to high (>=10) file descriptor to undo later
- // except if we're saving to environment variable instead (don't undo that)
- if ((hfd = next_hfd())==-1) return 1;
- if (hfd != dup2(to, hfd)) hfd = -1;
- else fcntl(hfd, F_SETFD, FD_CLOEXEC);
-
-if (BUGBUG) dprintf(255, "%d redir from=%d to=%d hfd=%d\n", getpid(), from, to, hfd);
- // dup "to"
- if (from != -1 && to != dup2(from, to)) {
- if (hfd != -1) close(hfd);
-
- return 1;
- }
-
- // Append undo information to redirect list so we can restore saved hfd later.
- if (!((cnt = *rd ? **rd : 0)&31)) *rd = xrealloc(*rd, (cnt+33)*2*sizeof(int));
- *(rr = *rd) = ++cnt;
- rr[2*cnt-1] = hfd;
- rr[2*cnt] = to;
-
- return 0;
-}
-
// Pipeline segments
struct sh_pipeline {
struct sh_pipeline *next, *prev;
@@ -615,59 +850,6 @@ struct sh_function {
char *end;
};
-// TODO: waitpid(WNOHANG) to clean up zombies and catch background& ending
-
-static void subshell_callback(void)
-{
- TT.subshell_env = xmprintf("@%d,%d=", getpid(), getppid());
- xsetenv(TT.subshell_env, 0);
- TT.subshell_env[strlen(TT.subshell_env)-1] = 0;
-}
-
-// TODO avoid prototype
-static int sh_run(char *new);
-
-// Pass environment and command string to child shell, return PID of child
-static int run_subshell(char *str, int len)
-{
- pid_t pid;
-
- // The with-mmu path is significantly faster.
- if (CFG_TOYBOX_FORK) {
- char *s;
-
- if ((pid = fork())<0) perror_msg("fork");
- else if (!pid) {
- s = xstrndup(str, len);
- sh_run(s);
- free(s);
-
- _exit(toys.exitval);
- }
-
- // On nommu vfork, exec /proc/self/exe, and pipe state data to ourselves.
- } else {
- int pipes[2], i;
-
- // open pipe to child
- if (pipe(pipes) || 254 != dup2(pipes[0], 254)) return 1;
- close(pipes[0]);
- fcntl(pipes[1], F_SETFD, FD_CLOEXEC);
-
- // vfork child
- pid = xpopen_setup(0, 0, subshell_callback);
-
- // marshall data to child
- close(254);
- if (TT.locals)
- for (i = 0; TT.locals[i]; i++) dprintf(pipes[1], "%s\n", TT.locals[i]);
- dprintf(pipes[1], "%.*s\n", len, str);
- close(pipes[1]);
- }
-
- return pid;
-}
-
// turn a parsed pipeline back into a string.
static char *pl2str(struct sh_pipeline *pl)
{
@@ -718,27 +900,19 @@ static struct sh_process *expand_redir(struct sh_arg *arg, int envlen, int *urd)
// Handle <() >() redirectionss
if ((*s == '<' || *s == '>') && s[1] == '(') {
- int pipes[2], *uu = 0, dd;
+ int new = pipe_subshell(s+2, strlen(s+1)-1, *s == '>');
// Grab subshell data
- if (pipe(pipes)) {
- perror_msg_raw(s);
+ if (new == -1) {
pp->exit = 1;
return pp;
}
-
- // Perform input or output redirect and launch process
- dd = *s == '<';
- save_redirect(&uu, pipes[dd], dd);
- close(pipes[dd]);
- run_subshell(s+2, strlen(s+2)-1); // ignore errors, don't track
- unredirect(uu);
- save_redirect(&urd, -1, pipes[!dd]);
+ save_redirect(&urd, -1, new);
// bash uses /dev/fd/%d which requires /dev/fd to be a symlink to
// /proc/self/fd so we just produce that directly.
- add_arg(&pp->delete, ss = xmprintf("/proc/self/fd/%d", pipes[!dd]));
+ add_arg(&pp->delete, ss = xmprintf("/proc/self/fd/%d", new));
array_add(&pp->arg.v, pp->arg.c++, ss);
continue;
@@ -1887,6 +2061,7 @@ void subshell_setup(void)
{
struct passwd *pw = getpwuid(getuid());
int to, from, pid = 0, ppid = 0, mypid, myppid, len;
+// TODO: you can unset readonly and these first 4 aren't malloc()
char *s, *ss, **ll, *locals[] = {"GROUPS=", "SECONDS=", "RANDOM=", "LINENO=",
xmprintf("PPID=%d", myppid = getppid()), xmprintf("EUID=%d", geteuid()),
xmprintf("$=%d", mypid = getpid()), xmprintf("UID=%d", getuid())};
@@ -1982,10 +2157,19 @@ void sh_main(void)
char *new;
struct sh_function scratch;
int prompt = 0;
+ struct sh_arg arg;
TT.hfd = 10;
signal(SIGPIPE, SIG_IGN);
+ TT.arg = &arg;
+ if (!(arg.c = toys.optc)) {
+ arg.v = xmalloc(2*sizeof(char *));
+ arg.v[arg.c++] = *toys.argv;
+ arg.v[arg.c] = 0;
+ } else memcpy(arg.v = xmalloc((arg.c+1)*sizeof(char *)), toys.optargs,
+ (arg.c+1)*sizeof(char *));
+
// TODO euid stuff?
// TODO login shell?
// TODO read profile, read rc