ash.c

这是一个SIGMA方案的PMP播放器的UCLINUX程序,可播放DVD,VCD,CD MP3...有很好的参考价值.

			i = 1;
		}
	}

	return (i);
}

static struct alias **
hashalias(const char *p)
{
	unsigned int hashval;

	hashval = *p << 4;
	while (*p)
		hashval+= *p++;
	return &atab[hashval % ATABSIZE];
}

static struct alias *
freealias(struct alias *ap)
{
	struct alias *next;

	if (ap->flag & ALIASINUSE) {
		ap->flag |= ALIASDEAD;
		return ap;
	}

	next = ap->next;
	ckfree(ap->name);
	ckfree(ap->val);
	ckfree(ap);
	return next;
}


static struct alias **
__lookupalias(const char *name)
{
	struct alias **app = hashalias(name);

	for (; *app; app = &(*app)->next) {
		if (equal(name, (*app)->name)) {
			break;
		}
	}

	return app;
}
#endif

#ifdef CONFIG_ASH_MATH_SUPPORT
/* The generated file arith.c has been replaced with a custom hand
 * written implementation written by Aaron Lehmann <[e-mail]>.
 * This is now part of libbb, so that it can be used by all the shells
 * in busybox. */
static void expari (int);
#endif

static char *trap[NSIG];                /* trap handler commands */
static char sigmode[NSIG - 1];  /* current value of signal */
static char gotsig[NSIG - 1];           /* indicates specified signal received */
static int pendingsigs;                 /* indicates some signal received */

/*
 * This file was generated by the mkbuiltins program.
 */

#ifdef CONFIG_ASH_JOB_CONTROL
static int bgcmd (int, char **);
static int fgcmd (int, char **);
static int killcmd (int, char **);
#endif
static int bltincmd (int, char **);
static int cdcmd (int, char **);
static int breakcmd (int, char **);
#ifdef CONFIG_ASH_CMDCMD
static int commandcmd (int, char **);
#endif
static int dotcmd (int, char **);
static int evalcmd (int, char **);
static int execcmd (int, char **);
static int exitcmd (int, char **);
static int exportcmd (int, char **);
static int histcmd (int, char **);
static int hashcmd (int, char **);
static int helpcmd (int, char **);
static int jobscmd (int, char **);
static int localcmd (int, char **);
static int pwdcmd (int, char **);
static int readcmd (int, char **);
static int returncmd (int, char **);
static int setcmd (int, char **);
static int setvarcmd (int, char **);
static int shiftcmd (int, char **);
static int trapcmd (int, char **);
static int umaskcmd (int, char **);
#ifdef CONFIG_ASH_ALIAS
static int aliascmd (int, char **);
static int unaliascmd (int, char **);
#endif
static int unsetcmd (int, char **);
static int waitcmd (int, char **);
static int ulimitcmd (int, char **);
static int timescmd (int, char **);
#ifdef CONFIG_ASH_MATH_SUPPORT
static int letcmd (int, char **);
#endif
static int typecmd (int, char **);
#ifdef CONFIG_ASH_GETOPTS
static int getoptscmd (int, char **);
#endif

#ifndef CONFIG_TRUE
static int true_main (int, char **);
#endif
#ifndef CONFIG_FALSE
static int false_main (int, char **);
#endif

static void     setpwd (const char *, int);


#define BUILTIN_NOSPEC  "0"
#define BUILTIN_SPECIAL "1"
#define BUILTIN_REGULAR "2"
#define BUILTIN_ASSIGN  "4"
#define BUILTIN_SPEC_ASSG  "5"
#define BUILTIN_REG_ASSG   "6"

#define IS_BUILTIN_SPECIAL(builtincmd) ((builtincmd)->name[0] & 1)
#define IS_BUILTIN_REGULAR(builtincmd) ((builtincmd)->name[0] & 2)
#define IS_BUILTIN_ASSIGN(builtincmd) ((builtincmd)->name[0] & 4)

struct builtincmd {
	const char *name;
	int (*const builtinfunc) (int, char **);
	//unsigned flags;
};


/* It is CRUCIAL that this listing be kept in ascii order, otherwise
 * the binary search in find_builtin() will stop working. If you value
 * your kneecaps, you'll be sure to *make sure* that any changes made
 * to this array result in the listing remaining in ascii order. You
 * have been warned.
 */
static const struct builtincmd builtincmds[] = {
	{ BUILTIN_SPECIAL   ".", dotcmd },    /* first, see declare DOTCMD */
	{ BUILTIN_SPECIAL   ":", true_main },
#ifdef CONFIG_ASH_ALIAS
	{ BUILTIN_REG_ASSG  "alias", aliascmd },
#endif
#ifdef CONFIG_ASH_JOB_CONTROL
	{ BUILTIN_REGULAR   "bg", bgcmd },
#endif
	{ BUILTIN_SPECIAL   "break", breakcmd },
	{ BUILTIN_SPECIAL   "builtin", bltincmd },
	{ BUILTIN_REGULAR   "cd", cdcmd },
	{ BUILTIN_NOSPEC    "chdir", cdcmd },
#ifdef CONFIG_ASH_CMDCMD
	{ BUILTIN_REGULAR   "command", commandcmd },
#endif
	{ BUILTIN_SPECIAL   "continue", breakcmd },
	{ BUILTIN_SPECIAL   "eval", evalcmd },
	{ BUILTIN_SPECIAL   "exec", execcmd },
	{ BUILTIN_SPECIAL   "exit", exitcmd },
	{ BUILTIN_SPEC_ASSG "export", exportcmd },
	{ BUILTIN_REGULAR   "false", false_main },
	{ BUILTIN_REGULAR   "fc", histcmd },
#ifdef CONFIG_ASH_JOB_CONTROL
	{ BUILTIN_REGULAR   "fg", fgcmd },
#endif
#ifdef CONFIG_ASH_GETOPTS
	{ BUILTIN_REGULAR   "getopts", getoptscmd },
#endif
	{ BUILTIN_NOSPEC    "hash", hashcmd },
	{ BUILTIN_NOSPEC    "help", helpcmd },
	{ BUILTIN_REGULAR   "jobs", jobscmd },
#ifdef CONFIG_ASH_JOB_CONTROL
	{ BUILTIN_REGULAR   "kill", killcmd },
#endif
#ifdef CONFIG_ASH_MATH_SUPPORT
	{ BUILTIN_REGULAR    "let", letcmd },
#endif
	{ BUILTIN_ASSIGN    "local", localcmd },
	{ BUILTIN_NOSPEC    "pwd", pwdcmd },
	{ BUILTIN_REGULAR   "read", readcmd },
	{ BUILTIN_SPEC_ASSG "readonly", exportcmd },
	{ BUILTIN_SPECIAL   "return", returncmd },
	{ BUILTIN_SPECIAL   "set", setcmd },
	{ BUILTIN_NOSPEC    "setvar", setvarcmd },
	{ BUILTIN_SPECIAL   "shift", shiftcmd },
	{ BUILTIN_SPECIAL   "times", timescmd },
	{ BUILTIN_SPECIAL   "trap", trapcmd },
	{ BUILTIN_REGULAR   "true", true_main },
	{ BUILTIN_NOSPEC    "type", typecmd },
	{ BUILTIN_NOSPEC    "ulimit", ulimitcmd },
	{ BUILTIN_REGULAR   "umask", umaskcmd },
#ifdef CONFIG_ASH_ALIAS
	{ BUILTIN_REGULAR   "unalias", unaliascmd },
#endif
	{ BUILTIN_SPECIAL   "unset", unsetcmd },
	{ BUILTIN_REGULAR   "wait", waitcmd },
};
#define NUMBUILTINS  (sizeof (builtincmds) / sizeof (struct builtincmd) )

#define DOTCMD &builtincmds[0]
static struct builtincmd *BLTINCMD;
static struct builtincmd *EXECCMD;
static struct builtincmd *EVALCMD;

/* states */
#define CONFIG_ASH_JOB_CONTROLTOPPED 1            /* all procs are stopped */
#define JOBDONE 2               /* all procs are completed */

/*
 * A job structure contains information about a job.  A job is either a
 * single process or a set of processes contained in a pipeline.  In the
 * latter case, pidlist will be non-NULL, and will point to a -1 terminated
 * array of pids.
 */

struct procstat {
	pid_t pid;              /* process id */
	int status;             /* status flags (defined above) */
	char *cmd;              /* text of command being run */
};


static int job_warning;         /* user was warned about stopped jobs */

#ifdef CONFIG_ASH_JOB_CONTROL
static void setjobctl(int enable);
#else
#define setjobctl(on)   /* do nothing */
#endif


struct job {
	struct procstat ps0;    /* status of process */
	struct procstat *ps;    /* status or processes when more than one */
	short nprocs;           /* number of processes */
	short pgrp;             /* process group of this job */
	char state;             /* true if job is finished */
	char used;              /* true if this entry is in used */
	char changed;           /* true if status has changed */
#ifdef CONFIG_ASH_JOB_CONTROL
	char jobctl;            /* job running under job control */
#endif
};

static struct job *jobtab;      /* array of jobs */
static int njobs;               /* size of array */
static int backgndpid = -1;     /* pid of last background process */
#ifdef CONFIG_ASH_JOB_CONTROL
static int initialpgrp;         /* pgrp of shell on invocation */
static int curjob;              /* current job */
static int jobctl;
#endif
static int intreceived;

static struct job *makejob (const union node *, int);
static int forkshell (struct job *, const union node *, int);
static int waitforjob (struct job *);

static int docd (char *, int);
static void getpwd (void);

static char *padvance (const char **, const char *);

static char nullstr[1];         /* zero length string */
static char *curdir = nullstr;          /* current working directory */

static int
cdcmd(int argc, char **argv)
{
	const char *dest;
	const char *path;
	char *p;
	struct stat statb;
	int print = 0;

	nextopt(nullstr);
	if ((dest = *argptr) == NULL && (dest = bltinlookup("HOME")) == NULL)
		error("HOME not set");
	if (*dest == '\0')
		dest = ".";
	if (dest[0] == '-' && dest[1] == '\0') {
		dest = bltinlookup("OLDPWD");
		if (!dest || !*dest) {
			dest = curdir;
		}
		print = 1;
		if (dest)
			print = 1;
		else
			dest = ".";
	}
	if (*dest == '/' || (path = bltinlookup("CDPATH")) == NULL)
		path = nullstr;
	while ((p = padvance(&path, dest)) != NULL) {
		if (stat(p, &statb) >= 0 && S_ISDIR(statb.st_mode)) {
			if (!print) {
				/*
				 * XXX - rethink
				 */
				if (p[0] == '.' && p[1] == '/' && p[2] != '\0')
					p += 2;
				print = strcmp(p, dest);
			}
			if (docd(p, print) >= 0)
				return 0;

		}
	}
	error("can't cd to %s", dest);
	/* NOTREACHED */
}


/*
 * Actually do the chdir.  In an interactive shell, print the
 * directory name if "print" is nonzero.
 */

static int
docd(char *dest, int print)
{
	TRACE(("docd(\"%s\", %d) called\n", dest, print));
	INTOFF;
	if (chdir(dest) < 0) {
		INTON;
		return -1;
	}
	hashcd();
	/*
	 * Update curdir (the name of the current directory) in response to a
	 * cd command.  We also call hashcd to let the routines in exec.c know
	 * that the current directory has changed.
	 */
	/* If dest is NULL, we don't know the current directory */
	if (dest == NULL || curdir == nullstr)
		setpwd(0, 1);
	else
		setpwd(dest, 1);

	INTON;
	if (print && iflag)
		puts(curdir);
	return 0;
}


static int
pwdcmd(int argc, char **argv)
{
	puts(curdir);
	return 0;
}

/* Ask system the current directory */
static void
getpwd(void)
{
	curdir = xgetcwd(0);
	if(curdir==0)
		curdir = nullstr;
}

static void
setpwd(const char *val, int setold)
{
	char *cated = NULL;

	if (setold) {
		setvar("OLDPWD", curdir, VEXPORT);
	}
	INTOFF;
	if (curdir != nullstr) {
		if(val!=NULL && *val != '/')
			val = cated = concat_path_file(curdir, val);
		free(curdir);
	}
	if (!val)
		getpwd();
	 else
		curdir = simplify_path(val);
	free(cated);
	INTON;
	setvar("PWD", curdir, VEXPORT);
}

/*
 * Errors and exceptions.
 */

/*
 * Code to handle exceptions in C.
 */

/*
 * We enclose jmp_buf in a structure so that we can declare pointers to
 * jump locations.  The global variable handler contains the location to
 * jump to when an exception occurs, and the global variable exception
 * contains a code identifying the exeception.  To implement nested
 * exception handlers, the user should save the value of handler on entry
 * to an inner scope, set handler to point to a jmploc structure for the
 * inner scope, and restore handler on exit from the scope.
 */

struct jmploc {
	jmp_buf loc;
};

/* exceptions */
#define EXINT 0         /* SIGINT received */
#define EXERROR 1       /* a generic error */
#define EXSHELLPROC 2   /* execute a shell procedure */
#define EXEXEC 3        /* command execution failed */

static struct jmploc *handler;
static int exception;

static void exverror (int, const char *, va_list)
    __attribute__((__noreturn__));

/*
 * Called to raise an exception.  Since C doesn't include exceptions, we
 * just do a longjmp to the exception handler.  The type of exception is
 * stored in the global variable "exception".
 */

static void exraise (int) __attribute__((__noreturn__));

static void
exraise(int e)
{
#ifdef DEBUG
	if (handler == NULL)
		abort();
#endif
	flushall();
	exception = e;
	longjmp(handler->loc, 1);
}


/*
 * Called from trap.c when a SIGINT is received.  (If the user specifies
 * that SIGINT is to be trapped or ignored using the trap builtin, then
 * this routine is not called.)  Suppressint is nonzero when interrupts
 * are held using the INTOFF macro.  The call to _exit is necessary because
 * there is a short period after a fork before the signal handlers are
 * set to the appropriate value for the child.  (The test for iflag is
 * just defensive programming.)
 */

static void
onint(void) {
	sigset_t mysigset;

	if (suppressint) {
		intpending++;
		return;
	}
	intpending = 0;
	sigemptyset(&mysigset);
	sigprocmask(SIG_SETMASK, &mysigset, NULL);
	if (rootshell && iflag)
		exraise(EXINT);
	else {
		signal(SIGINT, SIG_DFL);