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/*
 *  linux/fs/proc/proc_misc.c
 *
 *  linux/fs/proc/array.c
 *  Copyright (C) 1992  by Linus Torvalds
 *  based on ideas by Darren Senn
 *
 *  This used to be the part of array.c. See the rest of history and credits
 *  there. I took this into a separate file and switched the thing to generic
 *  proc_file_inode_operations, leaving in array.c only per-process stuff.
 *  Inumbers allocation made dynamic (via create_proc_entry()).  AV, May 1999.
 *
 * Changes:
 * Fulton Green      :  Encapsulated position metric calculations.
 *			<kernel@FultonGreen.com>
 */

#include <linux/types.h>
#include <linux/errno.h>
#include <linux/time.h>
#include <linux/kernel.h>
#include <linux/kernel_stat.h>
#include <linux/tty.h>
#include <linux/string.h>
#include <linux/mman.h>
#include <linux/proc_fs.h>
#include <linux/ioport.h>
#include <linux/config.h>
#include <linux/mm.h>
#include <linux/mmzone.h>
#include <linux/pagemap.h>
#include <linux/swap.h>
#include <linux/slab.h>
#include <linux/smp.h>
#include <linux/signal.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/smp_lock.h>
#include <linux/seq_file.h>
#include <linux/times.h>
#include <linux/profile.h>
#include <linux/blkdev.h>
#include <linux/hugetlb.h>
#include <linux/jiffies.h>
#include <linux/sysrq.h>
#include <linux/vmalloc.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/io.h>
#include <asm/pgalloc.h>
#include <asm/tlb.h>
#include <asm/div64.h>

#define LOAD_INT(x) ((x) >> FSHIFT)
#define LOAD_FRAC(x) LOAD_INT(((x) & (FIXED_1-1)) * 100)
/*
 * Warning: stuff below (imported functions) assumes that its output will fit
 * into one page. For some of those functions it may be wrong. Moreover, we
 * have a way to deal with that gracefully. Right now I used straightforward
 * wrappers, but this needs further analysis wrt potential overflows.
 */
extern int get_hardware_list(char *);
extern int get_stram_list(char *);
extern int get_chrdev_list(char *);
extern int get_blkdev_list(char *);
extern int get_filesystem_list(char *);
extern int get_exec_domain_list(char *);
extern int get_dma_list(char *);
extern int get_locks_status (char *, char **, off_t, int);
#ifdef CONFIG_SGI_DS1286
extern int get_ds1286_status(char *);
#endif

static int proc_calc_metrics(char *page, char **start, off_t off,
				 int count, int *eof, int len)
{
	if (len <= off+count) *eof = 1;
	*start = page + off;
	len -= off;
	if (len>count) len = count;
	if (len<0) len = 0;
	return len;
}

static int loadavg_read_proc(char *page, char **start, off_t off,
				 int count, int *eof, void *data)
{
	int a, b, c;
	int len;

	a = avenrun[0] + (FIXED_1/200);
	b = avenrun[1] + (FIXED_1/200);
	c = avenrun[2] + (FIXED_1/200);
	len = sprintf(page,"%d.%02d %d.%02d %d.%02d %ld/%d %d\n",
		LOAD_INT(a), LOAD_FRAC(a),
		LOAD_INT(b), LOAD_FRAC(b),
		LOAD_INT(c), LOAD_FRAC(c),
		nr_running(), nr_threads, last_pid);
	return proc_calc_metrics(page, start, off, count, eof, len);
}

struct vmalloc_info {
	unsigned long used;
	unsigned long largest_chunk;
};

static struct vmalloc_info get_vmalloc_info(void)
{
	unsigned long prev_end = VMALLOC_START;
	struct vm_struct* vma;
	struct vmalloc_info vmi;
	vmi.used = 0;

	read_lock(&vmlist_lock);

	if(!vmlist)
		vmi.largest_chunk = (VMALLOC_END-VMALLOC_START);
	else
		vmi.largest_chunk = 0;

	for (vma = vmlist; vma; vma = vma->next) {
		unsigned long free_area_size =
			(unsigned long)vma->addr - prev_end;
		vmi.used += vma->size;
		if (vmi.largest_chunk < free_area_size )

			vmi.largest_chunk = free_area_size;
		prev_end = vma->size + (unsigned long)vma->addr;
	}
	if(VMALLOC_END-prev_end > vmi.largest_chunk)
		vmi.largest_chunk = VMALLOC_END-prev_end;

	read_unlock(&vmlist_lock);
	return vmi;
}

static int uptime_read_proc(char *page, char **start, off_t off,
				 int count, int *eof, void *data)
{
	struct timespec uptime;
	struct timespec idle;
	int len;
	u64 idle_jiffies = init_task.utime + init_task.stime;

	do_posix_clock_monotonic_gettime(&uptime);
	jiffies_to_timespec(idle_jiffies, &idle);
	len = sprintf(page,"%lu.%02lu %lu.%02lu\n",
			(unsigned long) uptime.tv_sec,
			(uptime.tv_nsec / (NSEC_PER_SEC / 100)),
			(unsigned long) idle.tv_sec,
			(idle.tv_nsec / (NSEC_PER_SEC / 100)));

	return proc_calc_metrics(page, start, off, count, eof, len);
}

static int meminfo_read_proc(char *page, char **start, off_t off,
				 int count, int *eof, void *data)
{
	struct sysinfo i;
	int len, committed;
	struct page_state ps;
	unsigned long inactive;
	unsigned long active;
	unsigned long free;
	unsigned long vmtot;
	struct vmalloc_info vmi;

	get_page_state(&ps);
	get_zone_counts(&active, &inactive, &free);

/*
 * display in kilobytes.
 */
#define K(x) ((x) << (PAGE_SHIFT - 10))
	si_meminfo(&i);
	si_swapinfo(&i);
	committed = atomic_read(&vm_committed_space);

	vmtot = (VMALLOC_END-VMALLOC_START)>>10;
	vmi = get_vmalloc_info();
	vmi.used >>= 10;
	vmi.largest_chunk >>= 10;

	/*
	 * Tagged format, for easy grepping and expansion.
	 */
	len = sprintf(page,
		"MemTotal:     %8lu kB\n"
		"MemFree:      %8lu kB\n"
		"Buffers:      %8lu kB\n"
		"Cached:       %8lu kB\n"
		"SwapCached:   %8lu kB\n"
		"Active:       %8lu kB\n"
		"Inactive:     %8lu kB\n"
		"HighTotal:    %8lu kB\n"
		"HighFree:     %8lu kB\n"
		"LowTotal:     %8lu kB\n"
		"LowFree:      %8lu kB\n"
		"SwapTotal:    %8lu kB\n"
		"SwapFree:     %8lu kB\n"
		"Dirty:        %8lu kB\n"
		"Writeback:    %8lu kB\n"
		"Mapped:       %8lu kB\n"
		"Slab:         %8lu kB\n"
		"Committed_AS: %8u kB\n"
		"PageTables:   %8lu kB\n"
		"VmallocTotal: %8lu kB\n"
		"VmallocUsed:  %8lu kB\n"
		"VmallocChunk: %8lu kB\n",
		K(i.totalram),
		K(i.freeram),
		K(i.bufferram),
		K(get_page_cache_size()-total_swapcache_pages-i.bufferram),
		K(total_swapcache_pages),
		K(active),
		K(inactive),
		K(i.totalhigh),
		K(i.freehigh),
		K(i.totalram-i.totalhigh),
		K(i.freeram-i.freehigh),
		K(i.totalswap),
		K(i.freeswap),
		K(ps.nr_dirty),
		K(ps.nr_writeback),
		K(ps.nr_mapped),
		K(ps.nr_slab),
		K(committed),
		K(ps.nr_page_table_pages),
		vmtot,
		vmi.used,
		vmi.largest_chunk
		);

		len += hugetlb_report_meminfo(page + len);

	return proc_calc_metrics(page, start, off, count, eof, len);
#undef K
}

extern struct seq_operations fragmentation_op;
static int fragmentation_open(struct inode *inode, struct file *file)
{
	(void)inode;
	return seq_open(file, &fragmentation_op);
}

static struct file_operations fragmentation_file_operations = {
	.open		= fragmentation_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= seq_release,
};

static int version_read_proc(char *page, char **start, off_t off,
				 int count, int *eof, void *data)
{
	extern char *linux_banner;
	int len;

	strcpy(page, linux_banner);
	len = strlen(page);
	return proc_calc_metrics(page, start, off, count, eof, len);
}

extern struct seq_operations cpuinfo_op;
static int cpuinfo_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &cpuinfo_op);
}
static struct file_operations proc_cpuinfo_operations = {
	.open		= cpuinfo_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= seq_release,
};

extern struct seq_operations vmstat_op;
static int vmstat_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &vmstat_op);
}
static struct file_operations proc_vmstat_file_operations = {
	.open		= vmstat_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= seq_release,
};

#ifdef CONFIG_PROC_HARDWARE
static int hardware_read_proc(char *page, char **start, off_t off,
				 int count, int *eof, void *data)
{
	int len = get_hardware_list(page);
	return proc_calc_metrics(page, start, off, count, eof, len);
}
#endif

#ifdef CONFIG_STRAM_PROC
static int stram_read_proc(char *page, char **start, off_t off,
				 int count, int *eof, void *data)
{
	int len = get_stram_list(page);
	return proc_calc_metrics(page, start, off, count, eof, len);
}
#endif

extern struct seq_operations partitions_op;
static int partitions_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &partitions_op);
}
static struct file_operations proc_partitions_operations = {
	.open		= partitions_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= seq_release,
};

extern struct seq_operations diskstats_op;
static int diskstats_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &diskstats_op);
}
static struct file_operations proc_diskstats_operations = {
	.open		= diskstats_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= seq_release,
};

#ifdef CONFIG_MODULES
extern struct seq_operations modules_op;
static int modules_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &modules_op);
}
static struct file_operations proc_modules_operations = {
	.open		= modules_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= seq_release,
};
#endif

extern struct seq_operations slabinfo_op;
extern ssize_t slabinfo_write(struct file *, const char __user *, size_t, loff_t *);
static int slabinfo_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &slabinfo_op);
}
static struct file_operations proc_slabinfo_operations = {
	.open		= slabinfo_open,
	.read		= seq_read,
	.write		= slabinfo_write,
	.llseek		= seq_lseek,
	.release	= seq_release,
};

int show_stat(struct seq_file *p, void *v)
{
	int i;
	extern unsigned long total_forks;
	unsigned long jif;
	unsigned int sum = 0, user = 0, nice = 0, system = 0, idle = 0, iowait = 0, irq = 0, softirq = 0;

	jif = - wall_to_monotonic.tv_sec;
	if (wall_to_monotonic.tv_nsec)
		--jif;

	for_each_cpu(i) {
		int j;

		user += kstat_cpu(i).cpustat.user;
		nice += kstat_cpu(i).cpustat.nice;
		system += kstat_cpu(i).cpustat.system;
		idle += kstat_cpu(i).cpustat.idle;
		iowait += kstat_cpu(i).cpustat.iowait;
		irq += kstat_cpu(i).cpustat.irq;
		softirq += kstat_cpu(i).cpustat.softirq;
		for (j = 0 ; j < NR_IRQS ; j++)
			sum += kstat_cpu(i).irqs[j];
	}

	seq_printf(p, "cpu  %u %u %u %u %u %u %u\n",
		jiffies_to_clock_t(user),
		jiffies_to_clock_t(nice),
		jiffies_to_clock_t(system),
		jiffies_to_clock_t(idle),
		jiffies_to_clock_t(iowait),
		jiffies_to_clock_t(irq),
		jiffies_to_clock_t(softirq));
	for_each_online_cpu(i) {
		seq_printf(p, "cpu%d %u %u %u %u %u %u %u\n",
			i,
			jiffies_to_clock_t(kstat_cpu(i).cpustat.user),
			jiffies_to_clock_t(kstat_cpu(i).cpustat.nice),
			jiffies_to_clock_t(kstat_cpu(i).cpustat.system),
			jiffies_to_clock_t(kstat_cpu(i).cpustat.idle),
			jiffies_to_clock_t(kstat_cpu(i).cpustat.iowait),
			jiffies_to_clock_t(kstat_cpu(i).cpustat.irq),
			jiffies_to_clock_t(kstat_cpu(i).cpustat.softirq));
	}
	seq_printf(p, "intr %u", sum);

#if !defined(CONFIG_PPC64) && !defined(CONFIG_ALPHA)
	for (i = 0; i < NR_IRQS; i++)
		seq_printf(p, " %u", kstat_irqs(i));
#endif

	seq_printf(p,
		"\nctxt %lu\n"
		"btime %lu\n"
		"processes %lu\n"
		"procs_running %lu\n"
		"procs_blocked %lu\n",
		nr_context_switches(),
		(unsigned long)jif,
		total_forks,
		nr_running(),
		nr_iowait());

	return 0;
}

static int stat_open(struct inode *inode, struct file *file)
{
	unsigned size = 4096 * (1 + num_online_cpus() / 32);
	char *buf;
	struct seq_file *m;
	int res;

	/* don't ask for more than the kmalloc() max size, currently 128 KB */
	if (size > 128 * 1024)
		size = 128 * 1024;
	buf = kmalloc(size, GFP_KERNEL);
	if (!buf)
		return -ENOMEM;

	res = single_open(file, show_stat, NULL);
	if (!res) {
		m = file->private_data;
		m->buf = buf;
		m->size = size;
	} else
		kfree(buf);
	return res;
}
static struct file_operations proc_stat_operations = {
	.open		= stat_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= single_release,
};

static int devices_read_proc(char *page, char **start, off_t off,
				 int count, int *eof, void *data)
{
	int len = get_chrdev_list(page);
	len += get_blkdev_list(page+len);
	return proc_calc_metrics(page, start, off, count, eof, len);
}

/*
 * /proc/interrupts
 */
static void *int_seq_start(struct seq_file *f, loff_t *pos)
{
	return (*pos <= NR_IRQS) ? pos : NULL;
}

static void *int_seq_next(struct seq_file *f, void *v, loff_t *pos)
{
	(*pos)++;
	if (*pos > NR_IRQS)
		return NULL;
	return pos;
}

static void int_seq_stop(struct seq_file *f, void *v)
{
	/* Nothing to do */
}


extern int show_interrupts(struct seq_file *f, void *v); /* In arch code */
static struct seq_operations int_seq_ops = {
	.start = int_seq_start,
	.next  = int_seq_next,
	.stop  = int_seq_stop,
	.show  = show_interrupts
};

int interrupts_open(struct inode *inode, struct file *filp)
{
	return seq_open(filp, &int_seq_ops);
}

static struct file_operations proc_interrupts_operations = {
	.open		= interrupts_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= seq_release,
};

static int filesystems_read_proc(char *page, char **start, off_t off,
				 int count, int *eof, void *data)
{
	int len = get_filesystem_list(page);
	return proc_calc_metrics(page, start, off, count, eof, len);
}

static int cmdline_read_proc(char *page, char **start, off_t off,
				 int count, int *eof, void *data)
{
	extern char saved_command_line[];
	int len;

	len = sprintf(page, "%s\n", saved_command_line);
	return proc_calc_metrics(page, start, off, count, eof, len);
}

#ifdef CONFIG_SGI_DS1286
static int ds1286_read_proc(char *page, char **start, off_t off,
				 int count, int *eof, void *data)
{
	int len = get_ds1286_status(page);
	return proc_calc_metrics(page, start, off, count, eof, len);
}
#endif

static int locks_read_proc(char *page, char **start, off_t off,
				 int count, int *eof, void *data)
{
	int len = get_locks_status(page, start, off, count);

	if (len < count)
		*eof = 1;
	return len;
}

static int execdomains_read_proc(char *page, char **start, off_t off,
				 int count, int *eof, void *data)
{
	int len = get_exec_domain_list(page);
	return proc_calc_metrics(page, start, off, count, eof, len);
}

/*
 * This function accesses profiling information. The returned data is
 * binary: the sampling step and the actual contents of the profile
 * buffer. Use of the program readprofile is recommended in order to
 * get meaningful info out of these data.
 */
static ssize_t
read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
	unsigned long p = *ppos;
	ssize_t read;
	char * pnt;
	unsigned int sample_step = 1 << prof_shift;

	if (p >= (prof_len+1)*sizeof(unsigned int))
		return 0;
	if (count > (prof_len+1)*sizeof(unsigned int) - p)
		count = (prof_len+1)*sizeof(unsigned int) - p;
	read = 0;

	while (p < sizeof(unsigned int) && count > 0) {
		put_user(*((char *)(&sample_step)+p),buf);
		buf++; p++; count--; read++;
	}
	pnt = (char *)prof_buffer + p - sizeof(unsigned int);
	if (copy_to_user(buf,(void *)pnt,count))
		return -EFAULT;
	read += count;
	*ppos += read;
	return read;
}

/*
 * Writing to /proc/profile resets the counters
 *
 * Writing a 'profiling multiplier' value into it also re-sets the profiling
 * interrupt frequency, on architectures that support this.
 */
static ssize_t write_profile(struct file *file, const char __user *buf,
			     size_t count, loff_t *ppos)
{
#ifdef CONFIG_SMP
	extern int setup_profiling_timer (unsigned int multiplier);

	if (count == sizeof(int)) {
		unsigned int multiplier;

		if (copy_from_user(&multiplier, buf, sizeof(int)))
			return -EFAULT;

		if (setup_profiling_timer(multiplier))
			return -EINVAL;
	}
#endif

	memset(prof_buffer, 0, prof_len * sizeof(*prof_buffer));
	return count;
}

static struct file_operations proc_profile_operations = {
	.read		= read_profile,
	.write		= write_profile,
};

#ifdef CONFIG_MAGIC_SYSRQ
/*
 * writing 'C' to /proc/sysrq-trigger is like sysrq-C
 */
static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
				   size_t count, loff_t *ppos)
{
	if (count) {
		char c;

		if (get_user(c, buf))
			return -EFAULT;
		handle_sysrq(c, NULL, NULL);
	}
	return count;
}

static struct file_operations proc_sysrq_trigger_operations = {
	.write		= write_sysrq_trigger,
};
#endif

struct proc_dir_entry *proc_root_kcore;

static void create_seq_entry(char *name, mode_t mode, struct file_operations *f)
{
	struct proc_dir_entry *entry;
	entry = create_proc_entry(name, mode, NULL);
	if (entry)
		entry->proc_fops = f;
}

void __init proc_misc_init(void)
{
	struct proc_dir_entry *entry;
	static struct {
		char *name;
		int (*read_proc)(char*,char**,off_t,int,int*,void*);
	} *p, simple_ones[] = {
		{"loadavg",     loadavg_read_proc},
		{"uptime",	uptime_read_proc},
		{"meminfo",	meminfo_read_proc},
		{"version",	version_read_proc},
#ifdef CONFIG_PROC_HARDWARE
		{"hardware",	hardware_read_proc},
#endif
#ifdef CONFIG_STRAM_PROC
		{"stram",	stram_read_proc},
#endif
		{"devices",	devices_read_proc},
		{"filesystems",	filesystems_read_proc},
		{"cmdline",	cmdline_read_proc},
#ifdef CONFIG_SGI_DS1286
		{"rtc",		ds1286_read_proc},
#endif
		{"locks",	locks_read_proc},
		{"execdomains",	execdomains_read_proc},
		{NULL,}
	};
	for (p = simple_ones; p->name; p++)
		create_proc_read_entry(p->name, 0, NULL, p->read_proc, NULL);

	proc_symlink("mounts", NULL, "self/mounts");

	/* And now for trickier ones */
	entry = create_proc_entry("kmsg", S_IRUSR, &proc_root);
	if (entry)
		entry->proc_fops = &proc_kmsg_operations;
	create_seq_entry("cpuinfo", 0, &proc_cpuinfo_operations);
	create_seq_entry("partitions", 0, &proc_partitions_operations);
	create_seq_entry("stat", 0, &proc_stat_operations);
	create_seq_entry("interrupts", 0, &proc_interrupts_operations);
	create_seq_entry("slabinfo",S_IWUSR|S_IRUGO,&proc_slabinfo_operations);
	create_seq_entry("buddyinfo",S_IRUGO, &fragmentation_file_operations);
	create_seq_entry("vmstat",S_IRUGO, &proc_vmstat_file_operations);
	create_seq_entry("diskstats", 0, &proc_diskstats_operations);
#ifdef CONFIG_MODULES
	create_seq_entry("modules", 0, &proc_modules_operations);
#endif
#ifdef CONFIG_PROC_KCORE
	proc_root_kcore = create_proc_entry("kcore", S_IRUSR, NULL);
	if (proc_root_kcore) {
		proc_root_kcore->proc_fops = &proc_kcore_operations;
		proc_root_kcore->size =
				(size_t)high_memory - PAGE_OFFSET + PAGE_SIZE;
	}
#endif
	if (prof_on) {
		entry = create_proc_entry("profile", S_IWUSR | S_IRUGO, NULL);
		if (entry) {
			entry->proc_fops = &proc_profile_operations;
			entry->size = (1+prof_len) * sizeof(unsigned int);
		}
	}
#ifdef CONFIG_MAGIC_SYSRQ
	entry = create_proc_entry("sysrq-trigger", S_IWUSR, NULL);
	if (entry)
		entry->proc_fops = &proc_sysrq_trigger_operations;
#endif
#ifdef CONFIG_PPC32
	{
		extern struct file_operations ppc_htab_operations;
		entry = create_proc_entry("ppc_htab", S_IRUGO|S_IWUSR, NULL);
		if (entry)
			entry->proc_fops = &ppc_htab_operations;
	}
#endif
}



Tutorials

Linux System Admin Tips: There are over 200 Linux tips and tricks in this article. That is over 100 pages covering everything from NTP, setting up 2 IP address on one NIC, sharing directories among several users, putting running jobs in the background, find out who is doing what on your system by examining open sockets and the ps command, how to watch a file, how to prevent even root from deleting a file, tape commands, setting up cron jobs, using rsync, using screen conveniently with emacs, how to kill every process for a user, security tips and a lot more. These tip grow weekly. The above link will download the text version for easy grep searching. There is also an html version here.

Breaking Firewalls with OpenSSH and PuTTY: If the system administrator deliberately filters out all traffic except port 22 (ssh), to a single server, it is very likely that you can still gain access other computers behind the firewall. This article shows how remote Linux and Windows users can gain access to firewalled samba, mail, and http servers. In essence, it shows how openSSH and Putty can be used as a VPN solution for your home or workplace.

MySQL Tips and Tricks: Find out who is doing what in MySQL and how to kill the process, create binary log files, connect, create and select with Perl and Java, remove duplicates in a table with the index command, rollback and how to apply, merging several tables into one, updating foreign keys, monitor port 3306 with the tcpdump command, creating a C API, complex selects, and much more.

Create a Live Linux CD - BusyBox and OpenSSH Included: These steps will show you how to create a functioning Linux system, with the latest 2.6 kernel compiled from source, and how to integrate the BusyBox utilities including the installation of DHCP. Plus, how to compile in the OpenSSH package on this CD based system. On system boot-up a filesystem will be created and the contents from the CD will be uncompressed and completely loaded into RAM -- the CD could be removed at this point for boot-up on a second computer. The remaining functioning system will have full ssh capabilities. You can take over any PC assuming, of course, you have configured the kernel with the appropriate drivers and the PC can boot from a CD. This tutorial steps you through the whole processes.

SQLite Tutorial : This article explores the power and simplicity of sqlite3, first by starting with common commands and triggers, then the attach statement with the union operation is introduced in a way that allows multiple tables, in separate databases, to be combined as one virtual table, without the overhead of copying or moving data. Next, the simple sign function and the amazingly powerful trick of using this function in SQL select statements to solve complex queries with a single pass through the data is demonstrated, after making a brief mathematical case for how the sign function defines the absolute value and IF conditions.

The Lemon Parser Tutorial: This article explains how to build grammars and programs using the lemon parser, which is faster than yacc. And, unlike yacc, it is thread safe.

How to Compile the 2.6 kernel for Red Hat 9 and 8.0 and get Fedora Updates: This is a step by step tutorial on how to compile the 2.6 kernel from source.

Virtual Filesystem: Building A Linux Filesystem From An Ordinary File. You can take a disk file, format it as ext2, ext3, or reiser filesystem and then mount it, just like a physical drive. Yes, it then possible to read and write files to this newly mounted device. You can also copy the complete filesystem, since it is just a file, to another computer. If security is an issue, read on. This article will show you how to encrypt the filesystem, and mount it with ACL (Access Control Lists), which give you rights beyond the traditional read (r) write (w) and execute (x) for the 3 user groups file, owner and other.

Working With Time: What? There are 61 seconds in a minute? We can go back in time? We still tell time by the sun?



Chirico img Mike Chirico, a father of triplets (all girls) lives outside of Philadelphia, PA, USA. He has worked with Linux since 1996, has a Masters in Computer Science and Mathematics from Villanova University, and has worked in computer-related jobs from Wall Street to the University of Pennsylvania. His hero is Paul Erdos, a brilliant number theorist who was known for his open collaboration with others.


Mike's notes page is souptonuts. For open source consulting needs, please send an email to mchirico@gmail.com. All consulting work must include a donation to SourceForge.net.

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