w.c

linux下获取一些环境信息的代码

/* w - show what logged in users are doing.  Almost entirely rewritten from
 * scratch by Charles Blake circa June 1996.  Some vestigal traces of the
 * original may exist.  That was done in 1993 by Larry Greenfield with some
 * fixes by Michael K. Johnson.
 *
 * Changes by Albert Cahalan, 2002.
 */
#include "proc/version.h"
#include "proc/whattime.h"
#include "proc/readproc.h"
#include "proc/devname.h"
#include "proc/procps.h"
#include "proc/sysinfo.h"
#include "proc/escape.h"
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <pwd.h>
#include <time.h>
#include <unistd.h>
#include <utmp.h>
#include <locale.h>
#include <termios.h>

static int ignoreuser = 0;	/* for '-u' */
static proc_t **procs;		/* our snapshot of the process table */

typedef struct utmp utmp_t;

#ifdef W_SHOWFROM
#   define FROM_STRING "on"
#else
#   define FROM_STRING "off"
#endif

/* Uh... same thing as UT_NAMESIZE */
#define USERSZ (sizeof u->ut_user)


/* This routine is careful since some programs leave utmp strings
 * unprintable.  Always outputs at least 16 chars padded with spaces
 * on the right if necessary.
 */
static void print_host(const char *restrict host, int len) {
    const char *last;
    int width = 0;

    /* FIXME: there should really be a way to configure this... */
    /* for now, we'll just limit it to the 16 that the libc5 version
     * of utmp uses.
     */
    if (len > 16) len = 16;
    last = host + len;
    for ( ; host < last ; host++){
        if (isprint(*host) && *host != ' ') {
	    fputc(*host, stdout);
	    ++width;
	} else {
	    break;
	}
    }
    // space-fill, and a '-' too if needed to ensure the column exists
    if(width < 16) fputs("-               "+width, stdout);
}

/***** compact 7 char format for time intervals (belongs in libproc?) */
static void print_time_ival7(time_t t, int centi_sec, FILE* fout) {
    if((long)t < (long)0){  /* system clock changed? */
      printf("   ?   ");
      return;
    }
    if (t >= 48*60*60)				/* > 2 days */
	fprintf(fout, " %2ludays", t/(24*60*60));
    else if (t >= 60*60)			/* > 1 hour */
	fprintf(fout, " %2lu:%02um", t/(60*60), (unsigned) ((t/60)%60));
    else if (t > 60)				/* > 1 minute */
	fprintf(fout, " %2lu:%02u ", t/60, (unsigned) t%60);
    else
	fprintf(fout, " %2lu.%02us", t, centi_sec);
}

/**** stat the device file to get an idle time */
static time_t idletime(const char *restrict const tty) {
    struct stat sbuf;
    if (stat(tty, &sbuf) != 0)
	return 0;
    return time(NULL) - sbuf.st_atime;
}

/***** 7 character formatted login time */
static void print_logintime(time_t logt, FILE* fout) {
    char weekday[][4] = { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" },
	 month  [][4] = { "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul",
			"Aug", "Sep", "Oct", "Nov", "Dec" };
    time_t curt;
    struct tm *logtm, *curtm;
    int today;

    curt = time(NULL);
    curtm = localtime(&curt);
    /* localtime returns a pointer to static memory */
    today = curtm->tm_yday;
    logtm = localtime(&logt);
    if (curt - logt > 12*60*60 && logtm->tm_yday != today) {
	if (curt - logt > 6*24*60*60)
	    fprintf(fout, " %02d%3s%02d", logtm->tm_mday, month[logtm->tm_mon],
		    logtm->tm_year % 100);
	else
            fprintf(fout, " %3s%02d  ", weekday[logtm->tm_wday], logtm->tm_hour);
    } else {
        fprintf(fout, " %02d:%02d  ", logtm->tm_hour, logtm->tm_min);
    }
}


/* This function scans the process table accumulating total cpu times for
 * any processes "associated" with this login session.  It also searches
 * for the "best" process to report as "(w)hat" the user for that login
 * session is doing currently.  This the essential core of 'w'.
 */
static const proc_t *getproc(const utmp_t *restrict const u, const char *restrict const tty, unsigned long long *restrict const jcpu, int *restrict const found_utpid) {
    int line;
    proc_t **pptr = procs;
    const proc_t *best = NULL;
    const proc_t *secondbest = NULL;
    unsigned uid = ~0U;

    *found_utpid = 0;
    if(!ignoreuser){
	char buf[UT_NAMESIZE+1];
	struct passwd *passwd_data;   /* pointer to static data */
	strncpy(buf,u->ut_user,UT_NAMESIZE);
	buf[UT_NAMESIZE] = '\0';
	passwd_data = getpwnam(buf);
	if(!passwd_data) return NULL;
	uid = passwd_data->pw_uid;
	/* OK to have passwd_data go out of scope here */
    }
    line = tty_to_dev(tty);
    *jcpu = 0;
    for(; *pptr; pptr++) {
	const proc_t *restrict const tmp = *pptr;
	if(unlikely(tmp->tgid == u->ut_pid)) {
	    *found_utpid = 1;
	    best = tmp;
	}
	if(tmp->tty != line) continue;
	(*jcpu) += tmp->utime + tmp->stime;
	secondbest = tmp;
	/* same time-logic here as for "best" below */
	if(!  (secondbest && tmp->start_time <= secondbest->start_time)  ){
	    secondbest = tmp;
	}
	if(!ignoreuser && uid != tmp->euid && uid != tmp->ruid) continue;
	if(tmp->tgid != tmp->tpgid) continue;
	if(best && tmp->start_time <= best->start_time) continue;
    	best = tmp;
    }
    return best ? best : secondbest;
}


/***** showinfo */
static void showinfo(utmp_t *u, int formtype, int maxcmd, int from) {
    unsigned long long jcpu;
    int ut_pid_found;
    unsigned i;
    char uname[USERSZ + 1] = "",
	tty[5 + sizeof u->ut_line + 1] = "/dev/";
    const proc_t *best;

    for (i=0; i < sizeof(u->ut_line); i++)	/* clean up tty if garbled */
	if (isalnum(u->ut_line[i]) || (u->ut_line[i]=='/'))
	    tty[i+5] = u->ut_line[i];
	else
	    tty[i+5] = '\0';

    best = getproc(u, tty + 5, &jcpu, &ut_pid_found);

    /* just skip if stale utmp entry (i.e. login proc doesn't exist).  If there
     * is a desire a cmdline flag could be added to optionally show it with a
     * prefix of (stale) in front of cmd or something like that.
     */
    if (!ut_pid_found)
	return;

    strncpy(uname, u->ut_user, USERSZ);		/* force NUL term for printf */
    if (formtype) {
	printf("%-9.8s%-9.8s", uname, u->ut_line);
	if (from)
	    print_host(u->ut_host, sizeof u->ut_host);
	print_logintime(u->ut_time, stdout);
	if (*u->ut_line == ':')			/* idle unknown for xdm logins */
	    printf(" ?xdm? ");
	else
	    print_time_ival7(idletime(tty), 0, stdout);
	print_time_ival7(jcpu/Hertz, (jcpu%Hertz)*(100./Hertz), stdout);
	if (best) {
	    unsigned long long pcpu = best->utime + best->stime;
	    print_time_ival7(pcpu/Hertz, (pcpu%Hertz)*(100./Hertz), stdout);
	} else
	    printf("   ?   ");
    } else {
	printf("%-9.8s%-9.8s", u->ut_user, u->ut_line);
	if (from)
	    print_host(u->ut_host, sizeof u->ut_host);
	if (*u->ut_line == ':')			/* idle unknown for xdm logins */
	    printf(" ?xdm? ");
	else
	    print_time_ival7(idletime(tty), 0, stdout);
    }
    fputs(" ", stdout);
    if (likely(best)) {
	char cmdbuf[512];
	escape_command(cmdbuf, best, sizeof cmdbuf, &maxcmd, ESC_ARGS);
	fputs(cmdbuf,stdout);
    } else {
	printf("-");
    }
    fputc('\n', stdout);
}

/***** main */
int main(int argc, char **argv) {
    char *user = NULL;
    utmp_t *u;
    struct winsize win;
    int header=1, longform=1, from=1, args, maxcmd=80, ch;

#ifndef W_SHOWFROM
    from = 0;
#endif

    setlocale(LC_ALL, "");
    for (args=0; (ch = getopt(argc, argv, "hlusfV")) != EOF; args++)
	switch (ch) {
	  case 'h': header = 0;		break;
	  case 'l': longform = 1;	break;
	  case 's': longform = 0;	break;
	  case 'f': from = !from;	break;
	  case 'V': display_version();	exit(0);
	  case 'u': ignoreuser = 1;	break;
	  default:
	    printf("usage: w -hlsufV [user]\n"
		   "    -h    skip header\n"
		   "    -l    long listing (default)\n"
		   "    -s    short listing\n"
		   "    -u    ignore uid of processes\n"
		   "    -f    toggle FROM field (default %s)\n"
		   "    -V    display version\n", FROM_STRING);
	    exit(1);
	}

    if ((argv[optind]))
	user = (argv[optind]);

    if (ioctl(1, TIOCGWINSZ, &win) != -1 && win.ws_col > 0)
	maxcmd = win.ws_col;
    if (maxcmd < 71) {
	fprintf(stderr, "%d column window is too narrow\n", maxcmd);
	exit(1);
    }
    maxcmd -= 29 + (from ? 16 : 0) + (longform ? 20 : 0);
    if (maxcmd < 3)
	fprintf(stderr, "warning: screen width %d suboptimal.\n", win.ws_col);

    procs = readproctab(PROC_FILLCOM | PROC_FILLUSR | PROC_FILLSTAT);

    if (header) {				/* print uptime and headers */
	print_uptime();
	printf("USER     TTY      ");
	if (from)
	    printf("FROM            ");
	if (longform)
	    printf("  LOGIN@   IDLE   JCPU   PCPU WHAT\n");
	else
	    printf("   IDLE WHAT\n");
    }

    utmpname(UTMP_FILE);
    setutent();
    if (user) {
	for (;;) {
	    u = getutent();
	    if (unlikely(!u)) break;
	    if (u->ut_type != USER_PROCESS) continue;
 	    if (!strncmp(u->ut_user, user, USERSZ)) showinfo(u, longform, maxcmd, from);
	}
    } else {
	for (;;) {
	    u = getutent();
	    if (unlikely(!u)) break;
	    if (u->ut_type != USER_PROCESS) continue;
 	    if (*u->ut_user) showinfo(u, longform, maxcmd, from);
	}
    }
    endutent();

    return 0;
}