v19i007: A reimplementation of the System V shell, Part07/08
Rich Salz
rsalz at uunet.uu.net
Wed May 31 04:49:27 AEST 1989
Submitted-by: ka at june.cs.washington.edu (Kenneth Almquist)
Posting-number: Volume 19, Issue 7
Archive-name: ash/part07
# This is part 7 of ash. To unpack, feed it into the shell (not csh).
# The ash distribution consists of eight pieces. Be sure you get them all.
# After you unpack everything, read the file README.
echo extracting redir.h
cat > redir.h <<\EOF
/*
* Copyright (C) 1989 by Kenneth Almquist. All rights reserved.
* This file is part of ash, which is distributed under the terms specified
* by the Ash General Public License. See the file named LICENSE.
*/
/* flags passed to redirect */
#define REDIR_PUSH 01 /* save previous values of file descriptors */
#define REDIR_BACKQ 02 /* save the command output in memory */
#ifdef __STDC__
void redirect(union node *, int);
void popredir(void);
void clearredir(void);
int copyfd(int, int);
#else
void redirect();
void popredir();
void clearredir();
int copyfd();
#endif
EOF
if test `wc -c < redir.h` -ne 578
then echo 'redir.h is the wrong size'
fi
echo extracting redir.c
cat > redir.c <<\EOF
/*
* Code for dealing with input/output redirection.
*
* Copyright (C) 1989 by Kenneth Almquist. All rights reserved.
* This file is part of ash, which is distributed under the terms specified
* by the Ash General Public License. See the file named LICENSE.
*/
#include "shell.h"
#include "nodes.h"
#include "jobs.h"
#include "expand.h"
#include "redir.h"
#include "output.h"
#include "memalloc.h"
#include "error.h"
#include <signal.h>
#include <fcntl.h>
#include "myerrno.h"
#define EMPTY -2 /* marks an unused slot in redirtab */
#define PIPESIZE 4096 /* amount of buffering in a pipe */
MKINIT
struct redirtab {
struct redirtab *next;
short renamed[10];
};
MKINIT struct redirtab *redirlist;
#ifdef __STDC__
STATIC void openredirect(union node *, char *);
STATIC int openhere(union node *);
#else
STATIC void openredirect();
STATIC int openhere();
#endif
/*
* Process a list of redirection commands. If the REDIR_PUSH flag is set,
* old file descriptors are stashed away so that the redirection can be
* undone by calling popredir. If the REDIR_BACKQ flag is set, then the
* standard output, and the standard error if it becomes a duplicate of
* stdout, is saved in memory.
*/
void
redirect(redir, flags)
union node *redir;
int flags;
{
union node *n;
struct redirtab *sv;
int i;
int fd;
char memory[10]; /* file descriptors to write to memory */
for (i = 10 ; --i >= 0 ; )
memory[i] = 0;
memory[1] = flags & REDIR_BACKQ;
if (flags & REDIR_PUSH) {
sv = ckmalloc(sizeof (struct redirtab));
for (i = 0 ; i < 10 ; i++)
sv->renamed[i] = EMPTY;
sv->next = redirlist;
redirlist = sv;
}
for (n = redir ; n ; n = n->nfile.next) {
fd = n->nfile.fd;
if ((flags & REDIR_PUSH) && sv->renamed[fd] == EMPTY) {
INTOFF;
if ((i = copyfd(fd, 10)) != EMPTY) {
sv->renamed[fd] = i;
close(fd);
}
INTON;
if (i == EMPTY)
error("Out of file descriptors");
} else {
close(fd);
}
openredirect(n, memory);
}
if (memory[1])
out1 = &memout;
if (memory[2])
out2 = &memout;
}
STATIC void
openredirect(redir, memory)
union node *redir;
char memory[10];
{
int fd = redir->nfile.fd;
char *fname;
int f;
/*
* We suppress interrupts so that we won't leave open file
* descriptors around. This may not be such a good idea because
* an open of a device or a fifo can block indefinitely.
*/
INTOFF;
memory[fd] = 0;
switch (redir->nfile.type) {
case NFROM:
fname = redir->nfile.expfname;
if ((f = open(fname, O_RDONLY)) < 0)
error("cannot open %s: %s", fname, errmsg(errno, E_OPEN));
movefd:
if (f != fd) {
copyfd(f, fd);
close(f);
}
break;
case NTO:
fname = redir->nfile.expfname;
#ifdef O_CREAT
if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
error("cannot create %s: %s", fname, errmsg(errno, E_CREAT));
#else
if ((f = creat(fname, 0666)) < 0)
error("cannot create %s: %s", fname, errmsg(errno, E_CREAT));
#endif
goto movefd;
case NAPPEND:
fname = redir->nfile.expfname;
#ifdef O_APPEND
if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
error("cannot create %s: %s", fname, errmsg(errno, E_CREAT));
#else
if ((f = open(fname, O_WRONLY)) < 0
&& (f = creat(fname, 0666)) < 0)
error("cannot create %s: %s", fname, errmsg(errno, E_CREAT));
lseek(f, 0L, 2);
#endif
goto movefd;
case NTOFD:
case NFROMFD:
if (redir->ndup.dupfd >= 0) { /* if not ">&-" */
if (memory[redir->ndup.dupfd])
memory[fd] = 1;
else
copyfd(redir->ndup.dupfd, fd);
}
break;
case NHERE:
case NXHERE:
f = openhere(redir);
goto movefd;
default:
abort();
}
INTON;
}
/*
* Handle here documents. Normally we fork off a process to write the
* data to a pipe. If the document is short, we can stuff the data in
* the pipe without forking.
*/
STATIC int
openhere(redir)
union node *redir;
{
int pip[2];
int len;
if (pipe(pip) < 0)
error("Pipe call failed");
if (redir->type == NHERE) {
len = strlen(redir->nhere.doc->narg.text);
if (len <= PIPESIZE) {
xwrite(pip[1], redir->nhere.doc->narg.text, len);
goto out;
}
}
if (forkshell((struct job *)NULL, (union node *)NULL, FORK_NOJOB) == 0) {
close(pip[0]);
signal(SIGINT, SIG_IGN);
signal(SIGQUIT, SIG_IGN);
signal(SIGHUP, SIG_IGN);
#ifdef SIGTSTP
signal(SIGTSTP, SIG_IGN);
#endif
signal(SIGPIPE, SIG_DFL);
if (redir->type == NHERE)
xwrite(pip[1], redir->nhere.doc->narg.text, len);
else
expandhere(redir->nhere.doc, pip[1]);
_exit(0);
}
out:
close(pip[1]);
return pip[0];
}
/*
* Undo the effects of the last redirection.
*/
void
popredir() {
register struct redirtab *rp = redirlist;
int i;
for (i = 0 ; i < 10 ; i++) {
if (rp->renamed[i] != EMPTY) {
close(i);
if (rp->renamed[i] >= 0) {
copyfd(rp->renamed[i], i);
close(rp->renamed[i]);
}
}
}
INTOFF;
redirlist = rp->next;
ckfree(rp);
INTON;
}
/*
* Undo all redirections. Called on error or interrupt.
*/
#ifdef mkinit
INCLUDE "redir.h"
RESET {
while (redirlist)
popredir();
}
SHELLPROC {
clearredir();
}
#endif
/*
* Discard all saved file descriptors.
*/
void
clearredir() {
register struct redirtab *rp;
int i;
for (rp = redirlist ; rp ; rp = rp->next) {
for (i = 0 ; i < 10 ; i++) {
if (rp->renamed[i] >= 0) {
close(rp->renamed[i]);
}
rp->renamed[i] = EMPTY;
}
}
}
/*
* Copy a file descriptor, like the F_DUPFD option of fcntl. Returns -1
* if the source file descriptor is closed, EMPTY if there are no unused
* file descriptors left.
*/
int
copyfd(from, to) {
#ifdef F_DUPFD
int newfd;
newfd = fcntl(from, F_DUPFD, to);
if (newfd < 0 && errno == EMFILE)
return EMPTY;
return newfd;
#else
char toclose[32];
int i;
int newfd;
int e;
for (i = 0 ; i < to ; i++)
toclose[i] = 0;
INTOFF;
while ((newfd = dup(from)) >= 0 && newfd < to)
toclose[newfd] = 1;
e = errno;
for (i = 0 ; i < to ; i++) {
if (toclose[i])
close(i);
}
INTON;
if (newfd < 0 && e == EMFILE)
return EMPTY;
return newfd;
#endif
}
EOF
if test `wc -c < redir.c` -ne 6644
then echo 'redir.c is the wrong size'
fi
echo extracting shell.h.bsd
cat > shell.h.bsd <<\EOF
/*
* Copyright (C) 1989 by Kenneth Almquist. All rights reserved.
* This file is part of ash, which is distributed under the terms specified
* by the Ash General Public License. See the file named LICENSE.
*/
/*
* The follow should be set to reflect the type of system you have:
* JOBS -> 1 if you have Berkeley job control, 0 otherwise.
* SYMLINKS -> 1 if your system includes symbolic links, 0 otherwise.
* DIRENT -> 1 if your system has the SVR3 directory(3X) routines.
* UDIR -> 1 if you want the shell to simulate the /u directory.
* ATTY -> 1 to include code for atty(1).
* SHORTNAMES -> 1 if your linker cannot handle long names.
* define BSD if you are running 4.2 BSD or later.
* define SYSV if you are running under System V.
* define DEBUG to turn on debugging.
*
* When debugging is on, debugging info will be written to $HOME/trace and
* a quit signal will generate a core dump.
*/
#define JOBS 1
#define SYMLINKS 1
#define DIRENT 0
#define UDIR 1
#define ATTY 1
#define SHORTNAMES 0
#define BSD
/* #define SYSV */
/* #define DEBUG */
#if SHORTNAMES
#include "shortnames.h"
#endif
#ifdef __STDC__
typedef void *pointer;
#ifndef NULL
#define NULL (void *)0
#endif
#else /* not __STDC__ */
#define const
#define volatile
typedef char *pointer;
#ifndef NULL
#define NULL 0
#endif
#endif /* __STDC__ */
#define STATIC /* empty */
#define MKINIT /* empty */
extern char nullstr[1]; /* null string */
#ifdef DEBUG
#define TRACE(param) trace param
#else
#define TRACE(param)
#endif
EOF
if test `wc -c < shell.h.bsd` -ne 1520
then echo 'shell.h.bsd is the wrong size'
fi
echo extracting shell.h.s5r2
cat > shell.h.s5r2 <<\EOF
/*
* Copyright (C) 1989 by Kenneth Almquist. All rights reserved.
* This file is part of ash, which is distributed under the terms specified
* by the Ash General Public License. See the file named LICENSE.
*/
/*
* The follow should be set to reflect the type of system you have:
* JOBS -> 1 if you have Berkeley job control, 0 otherwise.
* SYMLINKS -> 1 if your system includes symbolic links, 0 otherwise.
* DIRENT -> 1 if your system has the SVR3 directory(3X) routines.
* UDIR -> 1 if you want the shell to simulate the /u directory.
* ATTY -> 1 to include code for atty(1).
* SHORTNAMES -> 1 if your linker cannot handle long names.
* define BSD if you are running 4.2 BSD or later.
* define SYSV if you are running under System V.
* define DEBUG to turn on debugging.
*
* When debugging is on, debugging info will be written to $HOME/trace and
* a quit signal will generate a core dump.
*/
#define JOBS 0
#define SYMLINKS 0
#define DIRENT 0
#define UDIR 1
#define ATTY 0
#define SHORTNAMES 0
/* #define BSD */
#define SYSV
/* #define DEBUG */
#if SHORTNAMES
#include "shortnames.h"
#endif
#ifdef __STDC__
typedef void *pointer;
#ifndef NULL
#define NULL (void *)0
#endif
#else /* not __STDC__ */
#define const
#define volatile
typedef char *pointer;
#ifndef NULL
#define NULL 0
#endif
#endif /* __STDC__ */
#define STATIC /* empty */
#define MKINIT /* empty */
extern char nullstr[1]; /* null string */
#ifdef DEBUG
#define TRACE(param) trace param
#else
#define TRACE(param)
#endif
EOF
if test `wc -c < shell.h.s5r2` -ne 1520
then echo 'shell.h.s5r2 is the wrong size'
fi
echo extracting shell.h.s5r3
cat > shell.h.s5r3 <<\EOF
/*
* Copyright (C) 1989 by Kenneth Almquist. All rights reserved.
* This file is part of ash, which is distributed under the terms specified
* by the Ash General Public License. See the file named LICENSE.
*/
/*
* The follow should be set to reflect the type of system you have:
* JOBS -> 1 if you have Berkeley job control, 0 otherwise.
* SYMLINKS -> 1 if your system includes symbolic links, 0 otherwise.
* DIRENT -> 1 if your system has the SVR3 directory(3X) routines.
* UDIR -> 1 if you want the shell to simulate the /u directory.
* ATTY -> 1 to include code for atty(1).
* SHORTNAMES -> 1 if your linker cannot handle long names.
* define BSD if you are running 4.2 BSD or later.
* define SYSV if you are running under System V.
* define DEBUG to turn on debugging.
*
* When debugging is on, debugging info will be written to $HOME/trace and
* a quit signal will generate a core dump.
*/
#define JOBS 0
#define SYMLINKS 0
#define DIRENT 1
#define UDIR 1
#define ATTY 0
#define SHORTNAMES 0
/* #define BSD */
#define SYSV
/* #define DEBUG */
#if SHORTNAMES
#include "shortnames.h"
#endif
#ifdef __STDC__
typedef void *pointer;
#ifndef NULL
#define NULL (void *)0
#endif
#else /* not __STDC__ */
#define const
#define volatile
typedef char *pointer;
#ifndef NULL
#define NULL 0
#endif
#endif /* __STDC__ */
#define STATIC /* empty */
#define MKINIT /* empty */
extern char nullstr[1]; /* null string */
#ifdef DEBUG
#define TRACE(param) trace param
#else
#define TRACE(param)
#endif
EOF
if test `wc -c < shell.h.s5r3` -ne 1520
then echo 'shell.h.s5r3 is the wrong size'
fi
echo extracting shortnames.h
cat > shortnames.h <<\EOF
/*
* Copyright (C) 1989 by Kenneth Almquist. All rights reserved.
* This file is part of ash, which is distributed under the terms specified
* by the Ash General Public License. See the file named LICENSE.
*
* The following defines avoid global name conflicts for linkers that
* only look at the first six characters.
*/
#define builtinfunc bltfu
#define builtinloc bltlo
#define cmdlookup cmdlk
#define command cmd_
#define commandtext cmdtx
#define delete_cmd_entry delce
#define environment envmt
#define expandarg exarg
#define expandhere exher
#define expandmeta exmet
#define growstackblock grosb
#define heredoclist herdl
#define lookupvar lookv
#define match_begin matcb
#define number_parens numpa
#define parsebackquote parbq
#define parsefile parfi
#define parsenextc parnx
#define parsenleft parnl
#define pushednleft pusnl
#define pushedstring pusst
#define readtoken1 rtok1
#define setinputfd stifd
#define setinputfile stifi
#define setinteractive stint
#define setvareq stveq
#define stacknleft stknl
EOF
if test `wc -c < shortnames.h` -ne 1027
then echo 'shortnames.h is the wrong size'
fi
echo extracting show.c
cat > show.c <<\EOF
/*
* Copyright (C) 1989 by Kenneth Almquist. All rights reserved.
* This file is part of ash, which is distributed under the terms specified
* by the Ash General Public License. See the file named LICENSE.
*/
#include <stdio.h>
#include "shell.h"
#include "parser.h"
#include "nodes.h"
#include "mystring.h"
#ifdef notdef
static shtree(), shcmd(), sharg(), indent();
showtree(n)
union node *n;
{
trputs("showtree called\n");
shtree(n, 1, NULL, stdout);
}
static
shtree(n, ind, pfx, fp)
union node *n;
char *pfx;
FILE *fp;
{
struct nodelist *lp;
char *s;
indent(ind, pfx, fp);
switch(n->type) {
case NSEMI:
s = "; ";
goto binop;
case NAND:
s = " && ";
goto binop;
case NOR:
s = " || ";
binop:
shtree(n->nbinary.ch1, ind, NULL, fp);
if (ind < 0)
fputs(s, fp);
shtree(n->nbinary.ch2, ind, NULL, fp);
break;
case NCMD:
shcmd(n, fp);
if (ind >= 0)
putc('\n', fp);
break;
case NPIPE:
for (lp = n->npipe.cmdlist ; lp ; lp = lp->next) {
shcmd(lp->n, fp);
if (lp->next)
fputs(" | ", fp);
}
if (n->npipe.backgnd)
fputs(" &", fp);
if (ind >= 0)
putc('\n', fp);
break;
default:
fprintf(fp, "<node type %d>", n->type);
if (ind >= 0)
putc('\n', fp);
break;
}
}
static
shcmd(cmd, fp)
union node *cmd;
FILE *fp;
{
union node *np;
int first;
char *s;
int dftfd;
first = 1;
for (np = cmd->ncmd.args ; np ; np = np->narg.next) {
if (! first)
putchar(' ');
sharg(np, fp);
first = 0;
}
for (np = cmd->ncmd.redirect ; np ; np = np->nfile.next) {
if (! first)
putchar(' ');
switch (np->nfile.type) {
case NTO: s = ">"; dftfd = 1; break;
case NAPPEND: s = ">>"; dftfd = 1; break;
case NTOFD: s = ">&"; dftfd = 1; break;
case NFROM: s = "<"; dftfd = 0; break;
case NFROMFD: s = "<&"; dftfd = 0; break;
}
if (np->nfile.fd != dftfd)
fprintf(fp, "%d", np->nfile.fd);
fputs(s, fp);
if (np->nfile.type == NTOFD || np->nfile.type == NFROMFD) {
fprintf(fp, "%d", np->nfile.dupfd);
} else {
sharg(np->nfile.fname, fp);
}
first = 0;
}
}
static
sharg(arg, fp)
union node *arg;
FILE *fp;
{
char *p;
struct nodelist *bqlist;
if (arg->type != NARG) {
printf("<node type %d>\n", arg->type);
fflush(stdout);
abort();
}
bqlist = arg->narg.backquote;
for (p = arg->narg.text ; *p ; p++) {
switch (*p) {
case CTLESC:
putc(*++p, fp);
break;
case CTLVAR:
case CTLVAR|CTLQUOTE:
putc('$', fp);
break;
case CTLBACKQ:
case CTLBACKQ|CTLQUOTE:
putc('`', fp);
shtree(bqlist->n, -1, NULL, fp);
putc('`', fp);
break;
default:
putc(*p, fp);
break;
}
}
}
static
indent(amount, pfx, fp)
char *pfx;
FILE *fp;
{
int i;
for (i = 0 ; i < amount ; i++) {
if (pfx && i == amount - 1)
fputs(pfx, fp);
putc('\t', fp);
}
}
#endif
/*
* Debugging stuff.
*/
FILE *tracefile;
trputc(c) {
#ifdef DEBUG
if (tracefile == NULL)
return;
putc(c, tracefile);
if (c == '\n')
fflush(tracefile);
#endif
}
trace(fmt, a1, a2, a3, a4, a5, a6, a7, a8)
char *fmt;
{
#ifdef DEBUG
if (tracefile == NULL)
return;
fprintf(tracefile, fmt, a1, a2, a3, a4, a5, a6, a7, a8);
if (strchr(fmt, '\n'))
fflush(tracefile);
#endif
}
trputs(s)
char *s;
{
#ifdef DEBUG
if (tracefile == NULL)
return;
fputs(s, tracefile);
if (strchr(s, '\n'))
fflush(tracefile);
#endif
}
trstring(s)
char *s;
{
register char *p;
char c;
#ifdef DEBUG
if (tracefile == NULL)
return;
putc('"', tracefile);
for (p = s ; *p ; p++) {
switch (*p) {
case '\n': c = 'n'; goto backslash;
case '\t': c = 't'; goto backslash;
case '\r': c = 'r'; goto backslash;
case '"': c = '"'; goto backslash;
case '\\': c = '\\'; goto backslash;
case CTLESC: c = 'e'; goto backslash;
case CTLVAR: c = 'v'; goto backslash;
case CTLVAR+CTLQUOTE: c = 'V'; goto backslash;
case CTLBACKQ: c = 'q'; goto backslash;
case CTLBACKQ+CTLQUOTE: c = 'Q'; goto backslash;
backslash: putc('\\', tracefile);
putc(c, tracefile);
break;
default:
if (*p >= ' ' && *p <= '~')
putc(*p, tracefile);
else {
putc('\\', tracefile);
putc(*p >> 6 & 03, tracefile);
putc(*p >> 3 & 07, tracefile);
putc(*p & 07, tracefile);
}
break;
}
}
putc('"', tracefile);
#endif
}
trargs(ap)
char **ap;
{
#ifdef DEBUG
if (tracefile == NULL)
return;
while (*ap) {
trstring(*ap++);
if (*ap)
putc(' ', tracefile);
else
putc('\n', tracefile);
}
fflush(tracefile);
#endif
}
opentrace() {
char s[100];
char *p;
char *getenv();
int flags;
#ifdef DEBUG
if ((p = getenv("HOME")) == NULL)
p = "/tmp";
scopy(p, s);
strcat(s, "/trace");
if ((tracefile = fopen(s, "a")) == NULL) {
fprintf(stderr, "Can't open %s\n", s);
exit(2);
}
#ifdef O_APPEND
if ((flags = fcntl(fileno(tracefile), F_GETFL, 0)) >= 0)
fcntl(fileno(tracefile), F_SETFL, flags | O_APPEND);
#endif
fputs("\nTracing started.\n", tracefile);
fflush(tracefile);
#endif
}
EOF
if test `wc -c < show.c` -ne 5655
then echo 'show.c is the wrong size'
fi
echo extracting trap.h
cat > trap.h <<\EOF
/*
* Copyright (C) 1989 by Kenneth Almquist. All rights reserved.
* This file is part of ash, which is distributed under the terms specified
* by the Ash General Public License. See the file named LICENSE.
*/
extern int sigpending;
#ifdef __STDC__
void clear_traps(void);
int setsignal(int);
void ignoresig(int);
void dotrap(void);
void setinteractive(int);
void exitshell(int);
#else
void clear_traps();
int setsignal();
void ignoresig();
void dotrap();
void setinteractive();
void exitshell();
#endif
EOF
if test `wc -c < trap.h` -ne 511
then echo 'trap.h is the wrong size'
fi
echo extracting trap.c
cat > trap.c <<\EOF
/*
* Routines for dealing with signals.
*
* Copyright (C) 1989 by Kenneth Almquist. All rights reserved.
* This file is part of ash, which is distributed under the terms specified
* by the Ash General Public License. See the file named LICENSE.
*/
#include "shell.h"
#include "main.h"
#include "nodes.h" /* for other headers */
#include "eval.h"
#include "jobs.h"
#include "options.h"
#include "syntax.h"
#include "signames.h"
#include "output.h"
#include "memalloc.h"
#include "error.h"
#include "trap.h"
#include "mystring.h"
#include <signal.h>
/*
* Sigmode records the current value of the signal handlers for the various
* modes. A value of zero means that the current handler is not known.
* S_HARD_IGN indicates that the signal was ignored on entry to the shell,
*/
#define S_DFL 1 /* default signal handling (SIG_DFL) */
#define S_CATCH 2 /* signal is caught */
#define S_IGN 3 /* signal is ignored (SIG_IGN) */
#define S_HARD_IGN 4 /* signal is ignored permenantly */
extern char nullstr[1]; /* null string */
char *trap[MAXSIG+1]; /* trap handler commands */
MKINIT char sigmode[MAXSIG]; /* current value of signal */
char gotsig[MAXSIG]; /* indicates specified signal received */
int sigpending; /* indicates some signal received */
#ifdef SYSV
typedef void (*sigaction)(); /* type returned by signal(2) */
#else
typedef int (*sigaction)(); /* type returned by signal(2) */
#endif
/*
* The trap builtin.
*/
trapcmd(argc, argv) char **argv; {
char *action;
char **ap;
int signo;
if (argc <= 1) {
for (signo = 0 ; signo <= MAXSIG ; signo++) {
if (trap[signo] != NULL)
out1fmt("%d: %s\n", signo, trap[signo]);
}
return 0;
}
ap = argv + 1;
if (is_number(*ap))
action = NULL;
else
action = *ap++;
while (*ap) {
if ((signo = number(*ap)) < 0 || signo > MAXSIG)
error("%s: bad trap", *ap);
INTOFF;
if (action)
action = savestr(action);
if (trap[signo])
ckfree(trap[signo]);
trap[signo] = action;
if (signo != 0)
setsignal(signo);
INTON;
ap++;
}
return 0;
}
/*
* Clear traps on a fork.
*/
void
clear_traps() {
char **tp;
for (tp = trap ; tp <= &trap[MAXSIG] ; tp++) {
if (*tp && **tp) { /* trap not NULL or SIG_IGN */
INTOFF;
ckfree(*tp);
*tp = NULL;
if (tp != &trap[0])
setsignal(tp - trap);
INTON;
}
}
}
/*
* Set the signal handler for the specified signal. The routine figures
* out what it should be set to.
*/
int
setsignal(signo) {
int action;
sigaction sigact;
char *t;
extern void onsig();
if ((t = trap[signo]) == NULL)
action = S_DFL;
else if (*t != '\0')
action = S_CATCH;
else
action = S_IGN;
if (rootshell && action == S_DFL) {
switch (signo) {
case SIGINT:
if (iflag)
action = S_CATCH;
break;
#ifndef DEBUG
case SIGQUIT:
#endif
case SIGTERM:
if (iflag)
action = S_IGN;
break;
#if JOBS
case SIGTSTP:
case SIGTTOU:
if (jflag)
action = S_IGN;
break;
#endif
}
}
t = &sigmode[signo - 1];
if (*t == 0) { /* current setting unknown */
/*
* There is a race condition here if action is not S_IGN.
* A signal can be ignored that shouldn't be.
*/
if ((int)(sigact = signal(signo, SIG_IGN)) == -1)
error("Signal system call failed");
if (sigact == SIG_IGN) {
*t = S_HARD_IGN;
} else {
*t = S_IGN;
}
}
if (*t == S_HARD_IGN || *t == action)
return 0;
switch (action) {
case S_DFL: sigact = SIG_DFL; break;
case S_CATCH: sigact = (sigaction)onsig; break;
case S_IGN: sigact = SIG_IGN; break;
}
*t = action;
return (int)signal(signo, sigact);
}
/*
* Ignore a signal.
*/
void
ignoresig(signo) {
if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN) {
signal(signo, SIG_IGN);
}
sigmode[signo - 1] = S_HARD_IGN;
}
#ifdef mkinit
INCLUDE "signames.h"
INCLUDE "trap.h"
SHELLPROC {
char *sm;
clear_traps();
for (sm = sigmode ; sm < sigmode + MAXSIG ; sm++) {
if (*sm == S_IGN)
*sm = S_HARD_IGN;
}
}
#endif
/*
* Signal handler.
*/
void
onsig(signo) {
signal(signo, (sigaction)onsig);
if (signo == SIGINT && trap[SIGINT] == NULL) {
onint();
return;
}
gotsig[signo - 1] = 1;
sigpending++;
}
/*
* Called to execute a trap. Perhaps we should avoid entering new trap
* handlers while we are executing a trap handler.
*/
void
dotrap() {
int i;
for (;;) {
for (i = 1 ; ; i++) {
if (gotsig[i - 1])
break;
if (i >= MAXSIG)
goto done;
}
gotsig[i - 1] = 0;
evalstring(trap[i]);
}
done:
sigpending = 0;
}
/*
* Controls whether the shell is interactive or not.
*/
int is_interactive;
void
setinteractive(on) {
if (on == is_interactive)
return;
setsignal(SIGINT);
setsignal(SIGQUIT);
setsignal(SIGTERM);
is_interactive = on;
}
/*
* Called to exit the shell.
*/
void
exitshell(status) {
struct jmploc loc1, loc2;
char *p;
TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
if (setjmp(loc1.loc)) goto l1;
if (setjmp(loc2.loc)) goto l2;
handler = &loc1;
if ((p = trap[0]) != NULL && *p != '\0') {
trap[0] = NULL;
evalstring(p);
}
l1: handler = &loc2; /* probably unnecessary */
flushall();
#if JOBS
setjobctl(0);
#endif
l2: _exit(status);
}
EOF
if test `wc -c < trap.c` -ne 6014
then echo 'trap.c is the wrong size'
fi
echo extracting var.h
cat > var.h <<\EOF
/*
* Shell variables.
*
* Copyright (C) 1989 by Kenneth Almquist. All rights reserved.
* This file is part of ash, which is distributed under the terms specified
* by the Ash General Public License. See the file named LICENSE.
*/
/* flags */
#define VEXPORT 01 /* variable is exported */
#define VREADONLY 02 /* variable cannot be modified */
#define VSTRFIXED 04 /* variable struct is staticly allocated */
#define VTEXTFIXED 010 /* text is staticly allocated */
#define VSTACK 020 /* text is allocated on the stack */
#define VUNSET 040 /* the variable is not set */
struct var {
struct var *next; /* next entry in hash list */
int flags; /* flags are defined above */
char *text; /* name=value */
};
struct localvar {
struct localvar *next; /* next local variable in list */
struct var *vp; /* the variable that was made local */
int flags; /* saved flags */
char *text; /* saved text */
};
struct localvar *localvars;
#if ATTY
extern struct var vatty;
#endif
extern struct var vifs;
extern struct var vmail;
extern struct var vmpath;
extern struct var vpath;
extern struct var vps1;
extern struct var vps2;
#if ATTY
extern struct var vterm;
#endif
/*
* The following macros access the values of the above variables.
* They have to skip over the name. They return the null string
* for unset variables.
*/
#define ifsval() (vifs.text + 4)
#define mailval() (vmail.text + 5)
#define mpathval() (vmpath.text + 9)
#define pathval() (vpath.text + 5)
#define ps1val() (vps1.text + 4)
#define ps2val() (vps2.text + 4)
#if ATTY
#define termval() (vterm.text + 5)
#endif
#if ATTY
#define attyset() ((vatty.flags & VUNSET) == 0)
#endif
#define mpathset() ((vmpath.flags & VUNSET) == 0)
#ifdef __STDC__
void initvar();
void setvar(char *, char *, int);
void setvareq(char *, int);
void listsetvar(struct strlist *);
char *lookupvar(char *);
char *bltinlookup(char *, int);
char **environment();
int showvarscmd(int, char **);
void mklocal(char *);
void poplocalvars(void);
#else
void initvar();
void setvar();
void setvareq();
void listsetvar();
char *lookupvar();
char *bltinlookup();
char **environment();
int showvarscmd();
void mklocal();
void poplocalvars();
#endif
EOF
if test `wc -c < var.h` -ne 2241
then echo 'var.h is the wrong size'
fi
echo extracting var.c
cat > var.c <<\EOF
/*
* Shell variables.
*
* Copyright (C) 1989 by Kenneth Almquist. All rights reserved.
* This file is part of ash, which is distributed under the terms specified
* by the Ash General Public License. See the file named LICENSE.
*/
#include "shell.h"
#include "output.h"
#include "expand.h"
#include "nodes.h" /* for other headers */
#include "eval.h" /* defines cmdenviron */
#include "exec.h"
#include "syntax.h"
#include "options.h"
#include "mail.h"
#include "var.h"
#include "memalloc.h"
#include "error.h"
#include "mystring.h"
#define VTABSIZE 39
struct varinit {
struct var *var;
int flags;
char *text;
};
#if ATTY
struct var vatty;
#endif
struct var vifs;
struct var vmail;
struct var vmpath;
struct var vpath;
struct var vps1;
struct var vps2;
struct var vvers;
#if ATTY
struct var vterm;
#endif
const struct varinit varinit[] = {
#if ATTY
{&vatty, VSTRFIXED|VTEXTFIXED|VUNSET, "ATTY="},
#endif
{&vifs, VSTRFIXED|VTEXTFIXED, "IFS= \t\n"},
{&vmail, VSTRFIXED|VTEXTFIXED|VUNSET, "MAIL="},
{&vmpath, VSTRFIXED|VTEXTFIXED|VUNSET, "MAILPATH="},
{&vpath, VSTRFIXED|VTEXTFIXED, "PATH=:/bin:/usr/bin"},
{&vps1, VSTRFIXED|VTEXTFIXED, "PS1=@ "},
{&vps2, VSTRFIXED|VTEXTFIXED, "PS2=> "},
{&vvers, VSTRFIXED|VTEXTFIXED, "SHELLVERS=ash 0.2"},
#if ATTY
{&vterm, VSTRFIXED|VTEXTFIXED|VUNSET, "TERM="},
#endif
{NULL, 0, NULL}
};
struct var *vartab[VTABSIZE];
#ifdef __STDC__
STATIC void unsetvar(char *);
STATIC struct var **hashvar(char *);
STATIC int varequal(char *, char *);
#else
STATIC void unsetvar();
STATIC struct var **hashvar();
STATIC int varequal();
#endif
/*
* Initialize the varable symbol tables and import the environment
*/
#ifdef mkinit
INCLUDE "var.h"
INIT {
char **envp;
extern char **environ;
initvar();
for (envp = environ ; *envp ; envp++) {
if (strchr(*envp, '=')) {
setvareq(*envp, VEXPORT|VTEXTFIXED);
}
}
}
#endif
/*
* This routine initializes the builtin variables. It is called when the
* shell is initialized and again when a shell procedure is spawned.
*/
void
initvar() {
const struct varinit *ip;
struct var *vp;
struct var **vpp;
for (ip = varinit ; (vp = ip->var) != NULL ; ip++) {
if ((vp->flags & VEXPORT) == 0) {
vpp = hashvar(ip->text);
vp->next = *vpp;
*vpp = vp;
vp->text = ip->text;
vp->flags = ip->flags;
}
}
}
/*
* Set the value of a variable. The flags argument is ored with the
* flags of the variable. If val is NULL, the variable is unset.
*/
void
setvar(name, val, flags)
char *name, *val;
{
char *p, *q;
int len;
int namelen;
char *nameeq;
int isbad;
isbad = 0;
p = name;
if (! is_name(*p++))
isbad = 1;
for (;;) {
if (! is_in_name(*p)) {
if (*p == '\0' || *p == '=')
break;
isbad = 1;
}
p++;
}
namelen = p - name;
if (isbad)
error("%.*s: is read only", namelen, name);
len = namelen + 2; /* 2 is space for '=' and '\0' */
if (val == NULL) {
flags |= VUNSET;
} else {
len += strlen(val);
}
p = nameeq = ckmalloc(len);
q = name;
while (--namelen >= 0)
*p++ = *q++;
*p++ = '=';
*p = '\0';
if (val)
scopy(val, p);
setvareq(nameeq, flags);
}
/*
* Same as setvar except that the variable and value are passed in
* the first argument as name=value. Since the first argument will
* be actually stored in the table, it should not be a string that
* will go away.
*/
void
setvareq(s, flags)
char *s;
{
struct var *vp, **vpp;
vpp = hashvar(s);
for (vp = *vpp ; vp ; vp = vp->next) {
if (varequal(s, vp->text)) {
if (vp->flags & VREADONLY) {
int len = strchr(s, '=') - s;
error("%.*s: is read only", len, s);
}
INTOFF;
if (vp == &vpath)
changepath(s + 5); /* 5 = strlen("PATH=") */
if ((vp->flags & (VTEXTFIXED|VSTACK)) == 0)
ckfree(vp->text);
vp->flags &=~ (VTEXTFIXED|VSTACK|VUNSET);
vp->flags |= flags;
vp->text = s;
if (vp == &vmpath || (vp == &vmail && ! mpathset()))
chkmail(1);
INTON;
return;
}
}
/* not found */
vp = ckmalloc(sizeof (*vp));
vp->flags = flags;
vp->text = s;
vp->next = *vpp;
*vpp = vp;
}
/*
* Process a linked list of variable assignments.
*/
void
listsetvar(list)
struct strlist *list;
{
struct strlist *lp;
INTOFF;
for (lp = list ; lp ; lp = lp->next) {
setvareq(savestr(lp->text), 0);
}
INTON;
}
/*
* Find the value of a variable. Returns NULL if not set.
*/
char *
lookupvar(name)
char *name;
{
struct var *v;
for (v = *hashvar(name) ; v ; v = v->next) {
if (varequal(v->text, name)) {
if (v->flags & VUNSET)
return NULL;
return strchr(v->text, '=') + 1;
}
}
return NULL;
}
/*
* Search the environment of a builtin command. If the second argument
* is nonzero, return the value of a variable even if it hasn't been
* exported.
*/
char *
bltinlookup(name, doall)
char *name;
{
struct strlist *sp;
struct var *v;
for (sp = cmdenviron ; sp ; sp = sp->next) {
if (varequal(sp->text, name))
return strchr(sp->text, '=') + 1;
}
for (v = *hashvar(name) ; v ; v = v->next) {
if (varequal(v->text, name)) {
if (v->flags & VUNSET
|| ! doall && (v->flags & VEXPORT) == 0)
return NULL;
return strchr(v->text, '=') + 1;
}
}
return NULL;
}
/*
* Generate a list of exported variables. This routine is used to construct
* the third argument to execve when executing a program.
*/
char **
environment() {
int nenv;
struct var **vpp;
struct var *vp;
char **env, **ep;
nenv = 0;
for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
for (vp = *vpp ; vp ; vp = vp->next)
if (vp->flags & VEXPORT)
nenv++;
}
ep = env = stalloc((nenv + 1) * sizeof *env);
for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
for (vp = *vpp ; vp ; vp = vp->next)
if (vp->flags & VEXPORT)
*ep++ = vp->text;
}
*ep = NULL;
return env;
}
/*
* Called when a shell procedure is invoked to clear out nonexported
* variables. It is also necessary to reallocate variables of with
* VSTACK set since these are currently allocated on the stack.
*/
#ifdef mkinit
MKINIT void shprocvar();
SHELLPROC {
shprocvar();
}
#endif
void
shprocvar() {
struct var **vpp;
struct var *vp, **prev;
for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
for (prev = vpp ; (vp = *prev) != NULL ; ) {
if ((vp->flags & VEXPORT) == 0) {
*prev = vp->next;
if ((vp->flags & VTEXTFIXED) == 0)
ckfree(vp->text);
if ((vp->flags & VSTRFIXED) == 0)
ckfree(vp);
} else {
if (vp->flags & VSTACK) {
vp->text = savestr(vp->text);
vp->flags &=~ VSTACK;
}
prev = &vp->next;
}
}
}
initvar();
}
/*
* Command to list all variables which are set. Currently this command
* is invoked from the set command when the set command is called without
* any variables.
*/
int
showvarscmd(argc, argv) char **argv; {
struct var **vpp;
struct var *vp;
for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
for (vp = *vpp ; vp ; vp = vp->next) {
if ((vp->flags & VUNSET) == 0)
out1fmt("%s\n", vp->text);
}
}
return 0;
}
/*
* The export and readonly commands.
*/
int
exportcmd(argc, argv) char **argv; {
struct var **vpp;
struct var *vp;
char *name;
char *p;
int flag = argv[0][0] == 'r'? VREADONLY : VEXPORT;
listsetvar(cmdenviron);
if (argc > 1) {
while ((name = *argptr++) != NULL) {
if ((p = strchr(name, '=')) != NULL) {
p++;
} else {
vpp = hashvar(name);
for (vp = *vpp ; vp ; vp = vp->next) {
if (varequal(vp->text, name)) {
vp->flags |= flag;
goto found;
}
}
}
setvar(name, p, flag);
found:;
}
} else {
for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
for (vp = *vpp ; vp ; vp = vp->next) {
if (vp->flags & flag) {
for (p = vp->text ; *p != '=' ; p++)
out1c(*p);
out1c('\n');
}
}
}
}
return 0;
}
/*
* The "local" command.
*/
localcmd(argc, argv) char **argv; {
char *name;
if (! in_function())
error("Not in a function");
while ((name = *argptr++) != NULL) {
mklocal(name);
}
return 0;
}
/*
* Make a variable a local variable. When a variable is made local, it's
* value and flags are saved in a localvar structure. The saved values
* will be restored when the shell function returns. We handle the name
* "-" as a special case.
*/
void
mklocal(name)
char *name;
{
struct localvar *lvp;
struct var **vpp;
struct var *vp;
INTOFF;
lvp = ckmalloc(sizeof (struct localvar));
if (name[0] == '-' && name[1] == '\0') {
lvp->text = ckmalloc(sizeof optval);
bcopy(optval, lvp->text, sizeof optval);
vp = NULL;
} else {
vpp = hashvar(name);
for (vp = *vpp ; vp && ! varequal(vp->text, name) ; vp = vp->next);
if (vp == NULL) {
if (strchr(name, '='))
setvareq(savestr(name), VSTRFIXED);
else
setvar(name, NULL, VSTRFIXED);
vp = *vpp; /* the new variable */
lvp->text = NULL;
lvp->flags = VUNSET;
} else {
lvp->text = vp->text;
lvp->flags = vp->flags;
vp->flags |= VSTRFIXED|VTEXTFIXED;
if (strchr(name, '='))
setvareq(savestr(name), 0);
}
}
lvp->vp = vp;
lvp->next = localvars;
localvars = lvp;
INTON;
}
/*
* Called after a function returns.
*/
void
poplocalvars() {
struct localvar *lvp;
struct var *vp;
while ((lvp = localvars) != NULL) {
localvars = lvp->next;
vp = lvp->vp;
if (vp == NULL) { /* $- saved */
bcopy(lvp->text, optval, sizeof optval);
ckfree(lvp->text);
} else if ((lvp->flags & (VUNSET|VSTRFIXED)) == VUNSET) {
unsetvar(vp->text);
} else {
if ((vp->flags & VTEXTFIXED) == 0)
ckfree(vp->text);
vp->flags = lvp->flags;
vp->text = lvp->text;
}
ckfree(lvp);
}
}
setvarcmd(argc, argv) char **argv; {
if (argc <= 2)
return unsetcmd(argc, argv);
else if (argc == 3)
setvar(argv[1], argv[2], 0);
else
error("List assignment not implemented");
return 0;
}
/*
* The unset builtin command. We unset the function before we unset the
* variable to allow a function to be unset when there is a readonly variable
* with the same name.
*/
unsetcmd(argc, argv) char **argv; {
char **ap;
for (ap = argv + 1 ; *ap ; ap++) {
unsetfunc(*ap);
unsetvar(*ap);
}
return 0;
}
/*
* Unset the specified variable.
*/
STATIC void
unsetvar(s)
char *s;
{
struct var **vpp;
struct var *vp;
vpp = hashvar(s);
for (vp = *vpp ; vp ; vpp = &vp->next, vp = *vpp) {
if (varequal(vp->text, s)) {
INTOFF;
if (*(strchr(vp->text, '=') + 1) != '\0'
|| vp->flags & VREADONLY) {
setvar(s, nullstr, 0);
}
vp->flags &=~ VEXPORT;
vp->flags |= VUNSET;
if ((vp->flags & VSTRFIXED) == 0) {
if ((vp->flags & VTEXTFIXED) == 0)
ckfree(vp->text);
*vpp = vp->next;
ckfree(vp);
}
INTON;
return;
}
}
}
/*
* Find the appropriate entry in the hash table from the name.
*/
STATIC struct var **
hashvar(p)
register char *p;
{
unsigned int hashval;
hashval = *p << 4;
while (*p && *p != '=')
hashval += *p++;
return &vartab[hashval % VTABSIZE];
}
/*
* Returns true if the two strings specify the same varable. The first
* variable name is terminated by '='; the second may be terminated by
* either '=' or '\0'.
*/
STATIC int
varequal(p, q)
register char *p, *q;
{
while (*p == *q++) {
if (*p++ == '=')
return 1;
}
if (*p == '=' && *(q - 1) == '\0')
return 1;
return 0;
}
EOF
if test `wc -c < var.c` -ne 12409
then echo 'var.c is the wrong size'
fi
echo extracting TOUR
cat > TOUR <<\EOF
A Tour through Ash
Copyright 1989 by Kenneth Almquist.
DIRECTORIES: The subdirectory bltin contains commands which can
be compiled stand-alone. The rest of the source is in the main
ash directory.
SOURCE CODE GENERATORS: Files whose names begin with "mk" are
programs that generate source code. A complete list of these
programs is:
program intput files generates
------- ------------ ---------
mkbuiltins builtins builtins.h builtins.c
mkinit *.c init.c
mknodes nodetypes nodes.h nodes.c
mksignames - signames.h signames.c
mksyntax - syntax.h syntax.c
mktokens - token.def
bltin/mkexpr unary_op binary_op operators.h operators.c
There are undoubtedly too many of these. Mkinit searches all the
C source files for entries looking like:
INIT {
x = 1; /* executed during initialization */
}
RESET {
x = 2; /* executed when the shell does a longjmp
back to the main command loop */
}
SHELLPROC {
x = 3; /* executed when the shell runs a shell procedure */
}
It pulls this code out into routines which are when particular
events occur. The intent is to improve modularity by isolating
the information about which modules need to be explicitly
initialized/reset within the modules themselves.
Mkinit recognizes several constructs for placing declarations in
the init.c file.
INCLUDE "file.h"
includes a file. The storage class MKINIT makes a declaration
available in the init.c file, for example:
MKINIT int funcnest; /* depth of function calls */
MKINIT alone on a line introduces a structure or union declara-
tion:
MKINIT
struct redirtab {
short renamed[10];
};
Preprocessor #define statements are copied to init.c without any
special action to request this.
INDENTATION: The ash source is indented in multiples of six
spaces. The only study that I have heard of on the subject con-
cluded that the optimal amount to indent is in the range of four
to six spaces. I use six spaces since it is not too big a jump
from the widely used eight spaces. If you really hate six space
indentation, use the adjind (source included) program to change
it to something else.
EXCEPTIONS: Code for dealing with exceptions appears in
exceptions.c. The C language doesn't include exception handling,
so I implement it using setjmp and longjmp. The global variable
exception contains the type of exception. EXERROR is raised by
calling error. EXINT is an interrupt. EXSHELLPROC is an excep-
tion which is raised when a shell procedure is invoked. The pur-
pose of EXSHELLPROC is to perform the cleanup actions associated
with other exceptions. After these cleanup actions, the shell
can interpret a shell procedure itself without exec'ing a new
copy of the shell.
INTERRUPTS: In an interactive shell, an interrupt will cause an
EXINT exception to return to the main command loop. (Exception:
EXINT is not raised if the user traps interrupts using the trap
command.) The INTOFF and INTON macros (defined in exception.h)
provide uninterruptable critical sections. Between the execution
of INTOFF and the execution of INTON, interrupt signals will be
held for later delivery. INTOFF and INTON can be nested.
MEMALLOC.C: Memalloc.c defines versions of malloc and realloc
which call error when there is no memory left. It also defines a
stack oriented memory allocation scheme. Allocating off a stack
is probably more efficient than allocation using malloc, but the
big advantage is that when an exception occurs all we have to do
to free up the memory in use at the time of the exception is to
restore the stack pointer. The stack is implemented using a
linked list of blocks.
STPUTC: If the stack were contiguous, it would be easy to store
strings on the stack without knowing in advance how long the
string was going to be:
p = stackptr;
*p++ = c; /* repeated as many times as needed */
stackptr = p;
The folloing three macros (defined in memalloc.h) perform these
operations, but grow the stack if you run off the end:
STARTSTACKSTR(p);
STPUTC(c, p); /* repeated as many times as needed */
grabstackstr(p);
We now start a top-down look at the code:
MAIN.C: The main routine performs some initialization, executes
the user's profile if necessary, and calls cmdloop. Cmdloop is
repeatedly parses and executes commands.
OPTIONS.C: This file contains the option processing code. It is
called from main to parse the shell arguments when the shell is
invoked, and it also contains the set builtin. The -i and -j op-
tions (the latter turns on job control) require changes in signal
handling. The routines setjobctl (in jobs.c) and setinteractive
(in trap.c) are called to handle changes to these options.
PARSING: The parser code is all in parser.c. A recursive des-
cent parser is used. Syntax tables (generated by mksyntax) are
used to classify characters during lexical analysis. There are
three tables: one for normal use, one for use when inside single
quotes, and one for use when inside double quotes. The tables
are machine dependent because they are indexed by character vari-
ables and the range of a char varies from machine to machine.
PARSE OUTPUT: The output of the parser consists of a tree of
nodes. The various types of nodes are defined in the file node-
types.
Nodes of type NARG are used to represent both words and the con-
tents of here documents. An early version of ash kept the con-
tents of here documents in temporary files, but keeping here do-
cuments in memory typically results in significantly better per-
formance. It would have been nice to make it an option to use
temporary files for here documents, for the benefit of small
machines, but the code to keep track of when to delete the tem-
porary files was complex and I never fixed all the bugs in it.
(AT&T has been maintaining the Bourne shell for more than ten
years, and to the best of my knowledge they still haven't gotten
it to handle temporary files correctly in obscure cases.)
The text field of a NARG structure points to the text of the
word. The text consists of ordinary characters and a number of
special codes defined in parser.h. The special codes are:
CTLVAR Variable substitution
CTLENDVAR End of variable substitution
CTLBACKQ Command substitution
CTLBACKQ|CTLQUOTE Command substitution inside double quotes
CTLESC Escape next character
A variable substitution contains the following elements:
CTLVAR type name '=' [ alternative-text CTLENDVAR ]
The type field is a single character specifying the type of sub-
stitution. The possible types are:
VSNORMAL $var
VSMINUS ${var-text}
VSMINUS|VSNUL ${var:-text}
VSPLUS ${var+text}
VSPLUS|VSNUL ${var:+text}
VSQUESTION ${var?text}
VSQUESTION|VSNUL ${var:?text}
VSASSIGN ${var=text}
VSASSIGN|VSNUL ${var=text}
In addition, the type field will have the VSQUOTE flag set if the
variable is enclosed in double quotes. The name of the variable
comes next, terminated by an equals sign. If the type is not
VSNORMAL, then the text field in the substitution follows, ter-
minated by a CTLENDVAR byte.
Commands in back quotes are parsed and stored in a linked list.
The locations of these commands in the string are indicated by
CTLBACKQ and CTLBACKQ+CTLQUOTE characters, depending upon whether
the back quotes were enclosed in double quotes.
The character CTLESC escapes the next character, so that in case
any of the CTL characters mentioned above appear in the input,
they can be passed through transparently. CTLESC is also used to
escape '*', '?', '[', and '!' characters which were quoted by the
user and thus should not be used for file name generation.
CTLESC characters have proved to be particularly tricky to get
right. In the case of here documents which are not subject to
variable and command substitution, the parser doesn't insert any
CTLESC characters to begin with (so the contents of the text
field can be written without any processing). Other here docu-
ments, and words which are not subject to splitting and file name
generation, have the CTLESC characters removed during the vari-
able and command substitution phase. Words which are subject
splitting and file name generation have the CTLESC characters re-
moved as part of the file name phase.
EXECUTION: Command execution is handled by the following files:
eval.c The top level routines.
redir.c Code to handle redirection of input and output.
jobs.c Code to handle forking, waiting, and job control.
exec.c Code to to path searches and the actual exec sys call.
expand.c Code to evaluate arguments.
var.c Maintains the variable symbol table. Called from expand.c.
EVAL.C: Evaltree recursively executes a parse tree. The exit
status is returned in the global variable exitstatus. The alter-
native entry evalbackcmd is called to evaluate commands in back
quotes. It saves the result in memory if the command is a buil-
tin; otherwise it forks off a child to execute the command and
connects the standard output of the child to a pipe.
JOBS.C: To create a process, you call makejob to return a job
structure, and then call forkshell (passing the job structure as
an argument) to create the process. Waitforjob waits for a job
to complete. These routines take care of process groups if job
control is defined.
REDIR.C: Ash allows file descriptors to be redirected and then
restored without forking off a child process. This is accom-
plished by duplicating the original file descriptors. The redir-
tab structure records where the file descriptors have be dupli-
cated to.
EXEC.C: The routine find_command locates a command, and enters
the command in the hash table if it is not already there. The
third argument specifies whether it is to print an error message
if the command is not found. (When a pipeline is set up,
find_command is called for all the commands in the pipeline be-
fore any forking is done, so to get the commands into the hash
table of the parent process. But to make command hashing as
transparent as possible, we silently ignore errors at that point
and only print error messages if the command cannot be found
later.)
The routine shellexec is the interface to the exec system call.
EXPAND.C: Arguments are processed in three passes. The first
(performed by the routine argstr) performs variable and command
substitution. The second (ifsbreakup) performs word splitting
and the third (expandmeta) performs file name generation. If the
"/u" directory is simulated, then when "/u/username" is replaced
by the user's home directory, the flag "didudir" is set. This
tells the cd command that it should print out the directory name,
just as it would if the "/u" directory were implemented using
symbolic links.
VAR.C: Variables are stored in a hash table. Probably we should
switch to extensible hashing. The variable name is stored in the
same string as the value (using the format "name=value") so that
no string copying is needed to create the environment of a com-
mand. Variables which the shell references internally are preal-
located so that the shell can reference the values of these vari-
ables without doing a lookup.
When a program is run, the code in eval.c sticks any environment
variables which precede the command (as in "PATH=xxx command") in
the variable table as the simplest way to strip duplicates, and
then calls "environment" to get the value of the environment.
There are two consequences of this. First, if an assignment to
PATH precedes the command, the value of PATH before the assign-
ment must be remembered and passed to shellexec. Second, if the
program turns out to be a shell procedure, the strings from the
environment variables which preceded the command must be pulled
out of the table and replaced with strings obtained from malloc,
since the former will automatically be freed when the stack (see
the entry on memalloc.c) is emptied.
BUILTIN COMMANDS: The procedures for handling these are scat-
tered throughout the code, depending on which location appears
most appropriate. They can be recognized because their names al-
ways end in "cmd". The mapping from names to procedures is
specified in the file builtins, which is processed by the mkbuil-
tins command.
A builtin command is invoked with argc and argv set up like a
normal program. A builtin command is allowed to overwrite its
arguments. Builtin routines can call nextopt to do option pars-
ing. This is kind of like getopt, but you don't pass argc and
argv to it. Builtin routines can also call error. This routine
normally terminates the shell (or returns to the main command
loop if the shell is interactive), but when called from a builtin
command it causes the builtin command to terminate with an exit
status of 2.
The directory bltins contains commands which can be compiled in-
dependently but can also be built into the shell for efficiency
reasons. The makefile in this directory compiles these programs
in the normal fashion (so that they can be run regardless of
whether the invoker is ash), but also creates a library named
bltinlib.a which can be linked with ash. The header file bltin.h
takes care of most of the differences between the ash and the
stand-alone environment. The user should call the main routine
"main", and #define main to be the name of the routine to use
when the program is linked into ash. This #define should appear
before bltin.h is included; bltin.h will #undef main if the pro-
gram is to be compiled stand-alone.
CD.C: This file defines the cd and pwd builtins. The pwd com-
mand runs /bin/pwd the first time it is invoked (unless the user
has already done a cd to an absolute pathname), but then
remembers the current directory and updates it when the cd com-
mand is run, so subsequent pwd commands run very fast. The main
complication in the cd command is in the docd command, which
resolves symbolic links into actual names and informs the user
where the user ended up if he crossed a symbolic link.
SIGNALS: Trap.c implements the trap command. The routine set-
signal figures out what action should be taken when a signal is
received and invokes the signal system call to set the signal ac-
tion appropriately. When a signal that a user has set a trap for
is caught, the routine "onsig" sets a flag. The routine dotrap
is called at appropriate points to actually handle the signal.
When an interrupt is caught and no trap has been set for that
signal, the routine "onint" in error.c is called.
OUTPUT: Ash uses it's own output routines. There are three out-
put structures allocated. "Output" represents the standard out-
put, "errout" the standard error, and "memout" contains output
which is to be stored in memory. This last is used when a buil-
tin command appears in backquotes, to allow its output to be col-
lected without doing any I/O through the UNIX operating system.
The variables out1 and out2 normally point to output and errout,
respectively, but they are set to point to memout when appropri-
ate inside backquotes.
INPUT: The basic input routine is pgetc, which reads from the
current input file. There is a stack of input files; the current
input file is the top file on this stack. The code allows the
input to come from a string rather than a file. (This is for the
-c option and the "." and eval builtin commands.) The global
variable plinno is saved and restored when files are pushed and
popped from the stack. The parser routines store the number of
the current line in this variable.
DEBUGGING: If DEBUG is defined in shell.h, then the shell will
write debugging information to the file $HOME/trace. Most of
this is done using the TRACE macro, which takes a set of printf
arguments inside two sets of parenthesis. Example:
"TRACE(("n=%d0, n))". The double parenthesis are necessary be-
cause the preprocessor can't handle functions with a variable
number of arguments. Defining DEBUG also causes the shell to
generate a core dump if it is sent a quit signal. The tracing
code is in show.c.
EOF
if test `wc -c < TOUR` -ne 16760
then echo 'TOUR is the wrong size'
fi
echo Archive 7 unpacked
exit
--
Please send comp.sources.unix-related mail to rsalz at uunet.uu.net.
Use a domain-based address or give alternate paths, or you may lose out.
More information about the Comp.sources.unix
mailing list