/*
 * Licensed under GPLv2, see file LICENSE in this source tree.
 *
 * Based on nanotop.c from floppyfw project
 *
 * Contact me: vda.linux@googlemail.com
 */
//config:config NMETER
//config:       bool "nmeter (11 kb)"
//config:       default y
//config:       help
//config:       Prints selected system stats continuously, one line per update.

//applet:IF_NMETER(APPLET(nmeter, BB_DIR_USR_BIN, BB_SUID_DROP))

//kbuild:lib-$(CONFIG_NMETER) += nmeter.o

//usage:#define nmeter_trivial_usage
//usage:       "[-d MSEC] FORMAT_STRING"
//usage:#define nmeter_full_usage "\n\n"
//usage:       "Monitor system in real time"
//usage:     "\n"
//usage:     "\n -d MSEC        Milliseconds between updates, default:1000, none:-1"
//usage:     "\n"
//usage:     "\nFormat specifiers:"
//usage:     "\n %Nc or %[cN]   CPU. N - bar size (default 10)"
//usage:     "\n                (displays: S:system U:user N:niced D:iowait I:irq i:softirq)"
//usage:     "\n %[nINTERFACE]  Network INTERFACE"
//usage:     "\n %m             Allocated memory"
//usage:     "\n %[mf]          Free memory"
//usage:     "\n %[mt]          Total memory"
//usage:     "\n %s             Allocated swap"
//usage:     "\n %f             Number of used file descriptors"
//usage:     "\n %Ni            Total/specific IRQ rate"
//usage:     "\n %x             Context switch rate"
//usage:     "\n %p             Forks"
//usage:     "\n %[pn]          # of processes"
//usage:     "\n %b             Block io"
//usage:     "\n %Nt            Time (with N decimal points)"
//usage:     "\n %NT            Zero-based timestamp (with N decimal points)"
//usage:     "\n %r             Print <cr> instead of <lf> at EOL"

//TODO:
// simplify code
// /proc/locks
// /proc/stat:
// disk_io: (3,0):(22272,17897,410702,4375,54750)
// btime 1059401962
//TODO: use sysinfo libc call/syscall, if appropriate
// (faster than open/read/close):
// sysinfo({uptime=15017, loads=[5728, 15040, 16480]
//  totalram=2107416576, freeram=211525632, sharedram=0, bufferram=157204480}
//  totalswap=134209536, freeswap=134209536, procs=157})

#include "libbb.h"
#include "common_bufsiz.h"

typedef unsigned long long ullong;

enum {  /* Preferably use powers of 2 */
        PROC_MIN_FILE_SIZE = 256,
        PROC_MAX_FILE_SIZE = 16 * 1024,
};

typedef struct proc_file {
        char *file;
        int file_sz;
        smallint last_gen;
} proc_file;

static const char *const proc_name[] = {
        "stat",         // Must match the order of proc_file's!
        "loadavg",
        "net/dev",
        "meminfo",
        "diskstats",
        "sys/fs/file-nr"
};

struct globals {
        // Sample generation flip-flop
        smallint gen;
        // Linux 2.6? (otherwise assumes 2.4)
        smallint is26;
        // 1 if sample delay is not an integer fraction of a second
        smallint need_seconds;
        char final_char;
        char *cur_outbuf;
        int delta;
        unsigned deltanz;
        struct timeval tv;
        struct timeval start;
#define first_proc_file proc_stat
        proc_file proc_stat;    // Must match the order of proc_name's!
        proc_file proc_loadavg;
        proc_file proc_net_dev;
        proc_file proc_meminfo;
        proc_file proc_diskstats;
        proc_file proc_sys_fs_filenr;
};
#define G (*ptr_to_globals)
#define gen                (G.gen               )
#define is26               (G.is26              )
#define need_seconds       (G.need_seconds      )
#define cur_outbuf         (G.cur_outbuf        )
#define proc_stat          (G.proc_stat         )
#define proc_loadavg       (G.proc_loadavg      )
#define proc_net_dev       (G.proc_net_dev      )
#define proc_meminfo       (G.proc_meminfo      )
#define proc_diskstats     (G.proc_diskstats    )
#define proc_sys_fs_filenr (G.proc_sys_fs_filenr)
#define outbuf bb_common_bufsiz1
#define INIT_G() do { \
        setup_common_bufsiz(); \
        SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
        cur_outbuf = outbuf; \
        G.final_char = '\n'; \
        G.deltanz = G.delta = 1000000; \
} while (0)

static inline void reset_outbuf(void)
{
        cur_outbuf = outbuf;
}

static void print_outbuf(void)
{
        int sz = cur_outbuf - outbuf;
        if (sz > 0) {
                xwrite(STDOUT_FILENO, outbuf, sz);
                cur_outbuf = outbuf;
        }
}

static void put(const char *s)
{
        char *p = cur_outbuf;
        int sz = outbuf + COMMON_BUFSIZE - p;
        while (*s && --sz >= 0)
                *p++ = *s++;
        cur_outbuf = p;
}

static void put_c(char c)
{
        if (cur_outbuf < outbuf + COMMON_BUFSIZE)
                *cur_outbuf++ = c;
}

static void put_question_marks(int count)
{
        while (count--)
                put_c('?');
}

static void readfile_z(proc_file *pf, const char* fname)
{
// open_read_close() will do two reads in order to be sure we are at EOF,
// and we don't need/want that.
        int fd;
        int sz, rdsz;
        char *buf;

        sz = pf->file_sz;
        buf = pf->file;
        if (!buf) {
                buf = xmalloc(PROC_MIN_FILE_SIZE);
                sz = PROC_MIN_FILE_SIZE;
        }
 again:
        fd = xopen(fname, O_RDONLY);
        buf[0] = '\0';
        rdsz = read(fd, buf, sz-1);
        close(fd);
        if (rdsz > 0) {
                if (rdsz == sz-1 && sz < PROC_MAX_FILE_SIZE) {
                        sz *= 2;
                        buf = xrealloc(buf, sz);
                        goto again;
                }
                buf[rdsz] = '\0';
        }
        pf->file_sz = sz;
        pf->file = buf;
}

static const char* get_file(proc_file *pf)
{
        if (pf->last_gen != gen) {
                pf->last_gen = gen;
                readfile_z(pf, proc_name[pf - &first_proc_file]);
        }
        return pf->file;
}

static ullong read_after_slash(const char *p)
{
        p = strchr(p, '/');
        if (!p) return 0;
        return strtoull(p+1, NULL, 10);
}

enum conv_type {
        conv_decimal = 0,
        conv_slash = 1
};

// Reads decimal values from line. Values start after key, for example:
// "cpu  649369 0 341297 4336769..." - key is "cpu" here.
// Values are stored in vec[].
// posbits is a bit lit of positions we are interested in.
// for example: 00100110 - we want 1st, 2nd and 5th value.
// posbits.bit0 encodes conversion type.
static int rdval(const char* p, const char* key, ullong *vec, long posbits)
{
        unsigned curpos;

        p = strstr(p, key);
        if (!p) return 1;

        p += strlen(key);
        curpos = 1 << 1;
        while (1) {
                while (*p == ' ' || *p == '\t') p++;
                if (*p == '\n' || *p == '\0') break;

                if (curpos & posbits) { // read this value
                        *vec++ = (posbits & 1) == conv_decimal ?
                                strtoull(p, NULL, 10) :
                                read_after_slash(p);
                        posbits -= curpos;
                        if (posbits <= 1)
                                return 0;
                }
                while (*p > ' ') // skip over the value
                        p++;
                curpos <<= 1;
        }
        return 0;
}

// Parses files with lines like "... ... ... 3/148 ...."
static int rdval_loadavg(const char* p, ullong *vec, long posbits)
{
        int result;
        result = rdval(p, "", vec, posbits | conv_slash);
        return result;
}

// Parses /proc/diskstats
//   1  2 3   4     5     6(rd)  7      8     9     10(wr) 11     12 13     14
//   3  0 hda 51292 14441 841783 926052 25717 79650 843256 3029804 0 148459 3956933
//   3  1 hda1 0 0 0 0 <- ignore if only 4 fields
// Linux 3.0 (maybe earlier) started printing full stats for hda1 too.
// Had to add code which skips such devices.
static int rdval_diskstats(const char* p, ullong *vec)
{
        char devname[32];
        unsigned devname_len = 0;
        int value_idx = 0;

        vec[0] = 0;
        vec[1] = 0;
        while (1) {
                value_idx++;
                while (*p == ' ' || *p == '\t')
                        p++;
                if (*p == '\0')
                        break;
                if (*p == '\n') {
                        value_idx = 0;
                        p++;
                        continue;
                }
                if (value_idx == 3) {
                        char *end = strchrnul(p, ' ');
                        /* If this a hda1-like device (same prefix as last one + digit)? */
                        if (devname_len && strncmp(devname, p, devname_len) == 0 && isdigit(p[devname_len])) {
                                p = end;
                                goto skip_line; /* skip entire line */
                        }
                        /* It is not. Remember the name for future checks */
                        devname_len = end - p;
                        if (devname_len > sizeof(devname)-1)
                                devname_len = sizeof(devname)-1;
                        strncpy(devname, p, devname_len);
                        /* devname[devname_len] = '\0'; - not really needed */
                        p = end;
                } else
                if (value_idx == 6) {
                        // TODO: *sectorsize (don't know how to find out sectorsize)
                        vec[0] += strtoull(p, NULL, 10);
                } else
                if (value_idx == 10) {
                        // TODO: *sectorsize (don't know how to find out sectorsize)
                        vec[1] += strtoull(p, NULL, 10);
 skip_line:
                        while (*p != '\n' && *p != '\0')
                                p++;
                        continue;
                }
                while ((unsigned char)(*p) > ' ') // skip over value
                        p++;
        }
        return 0;
}

static void scale(ullong ul)
{
        char buf[5];

        /* see http://en.wikipedia.org/wiki/Tera */
        smart_ulltoa4(ul, buf, " kmgtpezy")[0] = '\0';
        put(buf);
}

#define S_STAT(a) \
typedef struct a { \
        struct s_stat *next; \
        void (*collect)(struct a *s) FAST_FUNC; \
        const char *label;
#define S_STAT_END(a) } a;

S_STAT(s_stat)
S_STAT_END(s_stat)

static void FAST_FUNC collect_literal(s_stat *s UNUSED_PARAM)
{
}

static s_stat* init_literal(void)
{
        s_stat *s = xzalloc(sizeof(*s));
        s->collect = collect_literal;
        return (s_stat*)s;
}

static s_stat* init_cr(const char *param UNUSED_PARAM)
{
        G.final_char = '\r';
        return NULL;
}

//     user nice system idle  iowait irq  softirq (last 3 only in 2.6)
//cpu  649369 0 341297 4336769 11640 7122 1183
//cpuN 649369 0 341297 4336769 11640 7122 1183
enum { CPU_FIELDCNT = 7 };
S_STAT(cpu_stat)
        ullong old[CPU_FIELDCNT];
        unsigned bar_sz;
        char bar[1];
S_STAT_END(cpu_stat)

static void FAST_FUNC collect_cpu(cpu_stat *s)
{
        ullong data[CPU_FIELDCNT] = { 0, 0, 0, 0, 0, 0, 0 };
        unsigned frac[CPU_FIELDCNT] = { 0, 0, 0, 0, 0, 0, 0 };
        ullong all = 0;
        unsigned norm_all = 0;
        unsigned bar_sz = s->bar_sz;
        char *bar = s->bar;
        int i;

        if (rdval(get_file(&proc_stat), "cpu ", data, 0
            | (1 << 1)
            | (1 << 2)
            | (1 << 3)
            | (1 << 4)
            | (1 << 5)
            | (1 << 6)
            | (1 << 7))
        ) {
                put_question_marks(bar_sz);
                return;
        }

        for (i = 0; i < CPU_FIELDCNT; i++) {
                ullong old = s->old[i];
                if (data[i] < old) old = data[i];               //sanitize
                s->old[i] = data[i];
                all += (data[i] -= old);
        }

        if (all) {
                for (i = 0; i < CPU_FIELDCNT; i++) {
                        ullong t = bar_sz * data[i];
                        norm_all += data[i] = t / all;
                        frac[i] = t % all;
                }

                while (norm_all < bar_sz) {
                        unsigned max = frac[0];
                        int pos = 0;
                        for (i = 1; i < CPU_FIELDCNT; i++) {
                                if (frac[i] > max) max = frac[i], pos = i;
                        }
                        frac[pos] = 0;  //avoid bumping up same value twice
                        data[pos]++;
                        norm_all++;
                }

                memset(bar, '.', bar_sz);
                memset(bar, 'S', data[2]); bar += data[2]; //sys
                memset(bar, 'U', data[0]); bar += data[0]; //usr
                memset(bar, 'N', data[1]); bar += data[1]; //nice
                memset(bar, 'D', data[4]); bar += data[4]; //iowait
                memset(bar, 'I', data[5]); bar += data[5]; //irq
                memset(bar, 'i', data[6]); bar += data[6]; //softirq
        } else {
                memset(bar, '?', bar_sz);
        }
        put(s->bar);
}

static s_stat* init_cpu(const char *param)
{
        int sz;
        cpu_stat *s;
        sz = param[0] ? strtoul(param, NULL, 0) : 10;
        if (sz <= 0) sz = 1;
        if (sz > 1000) sz = 1000;
        s = xzalloc(sizeof(*s) + sz);
        /*s->bar[sz] = '\0'; - xzalloc did it */
        s->bar_sz = sz;
        s->collect = collect_cpu;
        return (s_stat*)s;
}

S_STAT(int_stat)
        ullong old;
        int no;
S_STAT_END(int_stat)

static void FAST_FUNC collect_int(int_stat *s)
{
        ullong data[1];
        ullong old;

        if (rdval(get_file(&proc_stat), "intr", data, 1 << s->no)) {
                put_question_marks(4);
                return;
        }

        old = s->old;
        if (data[0] < old) old = data[0];               //sanitize
        s->old = data[0];
        scale(data[0] - old);
}

static s_stat* init_int(const char *param)
{
        int_stat *s = xzalloc(sizeof(*s));
        s->collect = collect_int;
        if (param[0] == '\0') {
                s->no = 1;
        } else {
                int n = xatoi_positive(param);
                s->no = n + 2;
        }
        return (s_stat*)s;
}

S_STAT(ctx_stat)
        ullong old;
S_STAT_END(ctx_stat)

static void FAST_FUNC collect_ctx(ctx_stat *s)
{
        ullong data[1];
        ullong old;

        if (rdval(get_file(&proc_stat), "ctxt", data, 1 << 1)) {
                put_question_marks(4);
                return;
        }

        old = s->old;
        if (data[0] < old) old = data[0];               //sanitize
        s->old = data[0];
        scale(data[0] - old);
}

static s_stat* init_ctx(const char *param UNUSED_PARAM)
{
        ctx_stat *s = xzalloc(sizeof(*s));
        s->collect = collect_ctx;
        return (s_stat*)s;
}

S_STAT(blk_stat)
        const char* lookfor;
        ullong old[2];
S_STAT_END(blk_stat)

static void FAST_FUNC collect_blk(blk_stat *s)
{
        ullong data[2];
        int i;

        if (is26) {
                i = rdval_diskstats(get_file(&proc_diskstats), data);
        } else {
                i = rdval(get_file(&proc_stat), s->lookfor, data, 0
                                | (1 << 1)
                                | (1 << 2)
                );
                // Linux 2.4 reports bio in Kbytes, convert to sectors:
                data[0] *= 2;
                data[1] *= 2;
        }
        if (i) {
                put_question_marks(9);
                return;
        }

        for (i=0; i<2; i++) {
                ullong old = s->old[i];
                if (data[i] < old) old = data[i];               //sanitize
                s->old[i] = data[i];
                data[i] -= old;
        }
        scale(data[0]*512); // TODO: *sectorsize
        put_c(' ');
        scale(data[1]*512);
}

static s_stat* init_blk(const char *param UNUSED_PARAM)
{
        blk_stat *s = xzalloc(sizeof(*s));
        s->collect = collect_blk;
        s->lookfor = "page";
        return (s_stat*)s;
}

S_STAT(fork_stat)
        ullong old;
S_STAT_END(fork_stat)

static void FAST_FUNC collect_thread_nr(fork_stat *s UNUSED_PARAM)
{
        ullong data[1];

        if (rdval_loadavg(get_file(&proc_loadavg), data, 1 << 4)) {
                put_question_marks(4);
                return;
        }
        scale(data[0]);
}

static void FAST_FUNC collect_fork(fork_stat *s)
{
        ullong data[1];
        ullong old;

        if (rdval(get_file(&proc_stat), "processes", data, 1 << 1)) {
                put_question_marks(4);
                return;
        }

        old = s->old;
        if (data[0] < old) old = data[0];       //sanitize
        s->old = data[0];
        scale(data[0] - old);
}

static s_stat* init_fork(const char *param)
{
        fork_stat *s = xzalloc(sizeof(*s));
        if (*param == 'n') {
                s->collect = collect_thread_nr;
        } else {
                s->collect = collect_fork;
        }
        return (s_stat*)s;
}

S_STAT(if_stat)
        ullong old[4];
        const char *device;
        char *device_colon;
S_STAT_END(if_stat)

static void FAST_FUNC collect_if(if_stat *s)
{
        ullong data[4];
        int i;

        if (rdval(get_file(&proc_net_dev), s->device_colon, data, 0
            | (1 << 1)
            | (1 << 3)
            | (1 << 9)
            | (1 << 11))
        ) {
                put_question_marks(10);
                return;
        }

        for (i=0; i<4; i++) {
                ullong old = s->old[i];
                if (data[i] < old) old = data[i];               //sanitize
                s->old[i] = data[i];
                data[i] -= old;
        }
        put_c(data[1] ? '*' : ' ');
        scale(data[0]);
        put_c(data[3] ? '*' : ' ');
        scale(data[2]);
}

static s_stat* init_if(const char *device)
{
        if_stat *s = xzalloc(sizeof(*s));

        if (!device || !device[0])
                bb_show_usage();
        s->collect = collect_if;

        s->device = device;
        s->device_colon = xasprintf("%s:", device);
        return (s_stat*)s;
}

S_STAT(mem_stat)
        char opt;
S_STAT_END(mem_stat)

// "Memory" value should not include any caches.
// IOW: neither "ls -laR /" nor heavy read/write activity
//      should affect it. We'd like to also include any
//      long-term allocated kernel-side mem, but it is hard
//      to figure out. For now, bufs, cached & slab are
//      counted as "free" memory
//2.6.16:
//MemTotal:       773280 kB
//MemFree:         25912 kB - genuinely free
//Buffers:        320672 kB - cache
//Cached:         146396 kB - cache
//SwapCached:          0 kB
//Active:         183064 kB
//Inactive:       356892 kB
//HighTotal:           0 kB
//HighFree:            0 kB
//LowTotal:       773280 kB
//LowFree:         25912 kB
//SwapTotal:      131064 kB
//SwapFree:       131064 kB
//Dirty:              48 kB
//Writeback:           0 kB
//Mapped:          96620 kB
//Slab:           200668 kB - takes 7 Mb on my box fresh after boot,
//                            but includes dentries and inodes
//                            (== can take arbitrary amount of mem)
//CommitLimit:    517704 kB
//Committed_AS:   236776 kB
//PageTables:       1248 kB
//VmallocTotal:   516052 kB
//VmallocUsed:      3852 kB
//VmallocChunk:   512096 kB
//HugePages_Total:     0
//HugePages_Free:      0
//Hugepagesize:     4096 kB
static void FAST_FUNC collect_mem(mem_stat *s)
{
        ullong m_total = 0;
        ullong m_free = 0;
        ullong m_bufs = 0;
        ullong m_cached = 0;
        ullong m_slab = 0;

        if (rdval(get_file(&proc_meminfo), "MemTotal:", &m_total, 1 << 1)) {
                put_question_marks(4);
                return;
        }
        if (s->opt == 't') {
                scale(m_total << 10);
                return;
        }

        if (rdval(proc_meminfo.file, "MemFree:", &m_free  , 1 << 1)
         || rdval(proc_meminfo.file, "Buffers:", &m_bufs  , 1 << 1)
         || rdval(proc_meminfo.file, "Cached:",  &m_cached, 1 << 1)
         || rdval(proc_meminfo.file, "Slab:",    &m_slab  , 1 << 1)
        ) {
                put_question_marks(4);
                return;
        }

        m_free += m_bufs + m_cached + m_slab;
        switch (s->opt) {
        case 'f':
                scale(m_free << 10); break;
        default:
                scale((m_total - m_free) << 10); break;
        }
}

static s_stat* init_mem(const char *param)
{
        mem_stat *s = xzalloc(sizeof(*s));
        s->collect = collect_mem;
        s->opt = param[0];
        return (s_stat*)s;
}

S_STAT(swp_stat)
S_STAT_END(swp_stat)

static void FAST_FUNC collect_swp(swp_stat *s UNUSED_PARAM)
{
        ullong s_total[1];
        ullong s_free[1];
        if (rdval(get_file(&proc_meminfo), "SwapTotal:", s_total, 1 << 1)
         || rdval(proc_meminfo.file,       "SwapFree:" , s_free,  1 << 1)
        ) {
                put_question_marks(4);
                return;
        }
        scale((s_total[0]-s_free[0]) << 10);
}

static s_stat* init_swp(const char *param UNUSED_PARAM)
{
        swp_stat *s = xzalloc(sizeof(*s));
        s->collect = collect_swp;
        return (s_stat*)s;
}

S_STAT(fd_stat)
S_STAT_END(fd_stat)

static void FAST_FUNC collect_fd(fd_stat *s UNUSED_PARAM)
{
        ullong data[2];

        if (rdval(get_file(&proc_sys_fs_filenr), "", data, 0
            | (1 << 1)
            | (1 << 2))
        ) {
                put_question_marks(4);
                return;
        }

        scale(data[0] - data[1]);
}

static s_stat* init_fd(const char *param UNUSED_PARAM)
{
        fd_stat *s = xzalloc(sizeof(*s));
        s->collect = collect_fd;
        return (s_stat*)s;
}

S_STAT(time_stat)
        unsigned prec;
        unsigned scale;
S_STAT_END(time_stat)

static void FAST_FUNC collect_tv(time_stat *s, struct timeval *tv, int local)
{
        char buf[sizeof("12:34:56.123456")];
        struct tm* tm;
        unsigned us = tv->tv_usec + s->scale/2;
        time_t t = tv->tv_sec;

        if (us >= 1000000) {
                t++;
                us -= 1000000;
        }
        if (local)
                tm = localtime(&t);
        else
                tm = gmtime(&t);

        sprintf(buf, "%02u:%02u:%02u", tm->tm_hour, tm->tm_min, tm->tm_sec);
        if (s->prec)
                sprintf(buf+8, ".%0*u", s->prec, us / s->scale);
        put(buf);
}

static void FAST_FUNC collect_time(time_stat *s)
{
        collect_tv(s, &G.tv, /*local:*/ 1);
}

static void FAST_FUNC collect_monotonic(time_stat *s)
{
        struct timeval tv_mono;

        tv_mono.tv_sec = G.tv.tv_sec - G.start.tv_sec;
#if 0 /* Do we want this? */
        if (tv_mono.tv_sec < 0) {
                /* Time went backwards, reset start time to "now" */
                tv_mono.tv_sec = 0;
                G.start = G.tv;
        }
#endif
        tv_mono.tv_usec = G.tv.tv_usec - G.start.tv_usec;
        if ((int32_t)tv_mono.tv_usec < 0) {
                tv_mono.tv_usec += 1000000;
                tv_mono.tv_sec--;
        }
        collect_tv(s, &tv_mono, /*local:*/ 0);
}

static s_stat* init_time(const char *param)
{
        int prec;
        time_stat *s = xzalloc(sizeof(*s));

        s->collect = collect_time;
        prec = param[0] - '0';
        if (prec < 0) prec = 0;
        else if (prec > 6) prec = 6;
        s->prec = prec;
        s->scale = 1;
        while (prec++ < 6)
                s->scale *= 10;
        return (s_stat*)s;
}

static s_stat* init_monotonic(const char *param)
{
        time_stat *s = (void*)init_time(param);
        s->collect = collect_monotonic;
        return (s_stat*)s;
}

static void FAST_FUNC collect_info(s_stat *s)
{
        gen ^= 1;
        while (s) {
                put(s->label);
                s->collect(s);
                s = s->next;
        }
}

typedef s_stat* init_func(const char *param);

static const char options[] ALIGN1 = "ncmsfixptTbr";
static init_func *const init_functions[] ALIGN_PTR = {
        init_if,
        init_cpu,
        init_mem,
        init_swp,
        init_fd,
        init_int,
        init_ctx,
        init_fork,
        init_time,
        init_monotonic,
        init_blk,
        init_cr
};

int nmeter_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int nmeter_main(int argc UNUSED_PARAM, char **argv)
{
        char buf[32];
        s_stat *first = NULL;
        s_stat *last = NULL;
        s_stat *s;
        char *opt_d;
        char *cur, *prev;

        INIT_G();

        xchdir("/proc");

        if (open_read_close("version", buf, sizeof(buf)-1) > 0) {
                buf[sizeof(buf)-1] = '\0';
                is26 = (strstr(buf, " 2.4.") == NULL);
        }

        if (getopt32(argv, "d:", &opt_d)) {
                G.delta = xatoi(opt_d) * 1000;
                G.deltanz = G.delta > 0 ? G.delta : 1;
                need_seconds = (1000000 % G.deltanz) != 0;
        }
        argv += optind;

        if (!argv[0])
                bb_show_usage();

        // Can use argv[0] directly, but this will mess up
        // parameters as seen by e.g. ps. Making a copy...
        cur = xstrdup(argv[0]);
        while (1) {
                char *param, *p;
                prev = cur;
 again:
                cur = strchr(cur, '%');
                if (!cur)
                        break;
                if (cur[1] == '%') {    // %%
                        overlapping_strcpy(cur, cur + 1);
                        cur++;
                        goto again;
                }
                *cur++ = '\0';          // overwrite %
                if (cur[0] == '[') {
                        // format: %[foptstring]
                        cur++;
                        p = strchr(options, cur[0]);
                        param = cur+1;
                        while (cur[0] != ']') {
                                if (!cur[0])
                                        bb_show_usage();
                                cur++;
                        }
                        *cur++ = '\0';  // overwrite [
                } else {
                        // format: %NNNNNNf
                        param = cur;
                        while (cur[0] >= '0' && cur[0] <= '9')
                                cur++;
                        if (!cur[0])
                                bb_show_usage();
                        p = strchr(options, cur[0]);
                        *cur++ = '\0';  // overwrite format char
                }
                if (!p)
                        bb_show_usage();
                s = init_functions[p-options](param);
                if (s) {
                        s->label = prev;
                        /*s->next = NULL; - all initXXX funcs use xzalloc */
                        if (!first)
                                first = s;
                        else
                                last->next = s;
                        last = s;
                } else {
                        // %r option. remove it from string
                        overlapping_strcpy(prev + strlen(prev), cur);
                        cur = prev;
                }
        }
        if (prev[0]) {
                s = init_literal();
                s->label = prev;
                /*s->next = NULL; - all initXXX funcs use xzalloc */
                if (!first)
                        first = s;
                else
                        last->next = s;
                last = s;
        }

        // Generate first samples but do not print them, they're bogus
        collect_info(first);
        reset_outbuf();

        if (G.delta >= 0) {
                xgettimeofday(&G.tv);
                usleep(G.delta > 1000000 ? 1000000 : G.delta - G.tv.tv_usec % G.deltanz);
        }

        xgettimeofday(&G.start);
        G.tv = G.start;
        while (1) {
                collect_info(first);
                put_c(G.final_char);
                print_outbuf();

                // Negative delta -> no usleep at all
                // This will hog the CPU but you can have REALLY GOOD
                // time resolution ;)
                // TODO: detect and avoid useless updates
                // (like: nothing happens except time)
                if (G.delta >= 0) {
                        int rem;
                        // can be commented out, will sacrifice sleep time precision a bit
                        xgettimeofday(&G.tv);
                        if (need_seconds)
                                rem = G.delta - ((ullong)G.tv.tv_sec*1000000 + G.tv.tv_usec) % G.deltanz;
                        else
                                rem = G.delta - (unsigned)G.tv.tv_usec % G.deltanz;
                        // Sometimes kernel wakes us up just a tiny bit earlier than asked
                        // Do not go to very short sleep in this case
                        if (rem < (unsigned)G.delta / 128) {
                                rem += G.delta;
                        }
                        usleep(rem);
                }
                xgettimeofday(&G.tv);
        }

        /*return 0;*/
}