/*
 * Copyright 1998 by Albert Cahalan; all rights reserved.
 * This file may be used subject to the terms and conditions of the
 * GNU Library General Public License Version 2, or any later version
 * at your option, as published by the Free Software Foundation.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Library General Public License for more details.
 */

/* This is a minimal /bin/ps, designed to be smaller than the old ps
 * while still supporting some of the more important features of the
 * new ps. (for total size, note that this ps does not need libproc)
 * It is suitable for Linux-on-a-floppy systems only.
 *
 * Maintainers: do not compile or install for normal systems.
 * Anyone needing this will want to tweak their compiler anyway.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <dirent.h>
#include <unistd.h>

#include <asm/param.h>		/* HZ */

static int P_euid;
static int P_pid;
static char P_cmd[16];
static char P_state;
static int P_ppid, P_pgrp, P_session, P_tty, P_tpgid;
static unsigned long P_flags, P_min_flt, P_cmin_flt, P_maj_flt, P_cmaj_flt,
    P_utime, P_stime;
static long P_cutime, P_cstime, P_priority, P_nice, P_timeout, P_it_real_value;
static unsigned long P_start_time, P_vsize;
static long P_rss;
static unsigned long P_rss_rlim, P_start_code, P_end_code, P_start_stack,
    P_kstk_esp, P_kstk_eip;
static unsigned P_signal, P_blocked, P_sigignore, P_sigcatch;
static unsigned long P_wchan, P_nswap, P_cnswap;

#if 0
static int screen_cols = 80;
static int w_count;
#endif

static int want_one_pid;
static const char *want_one_command;
static int select_notty;
static int select_all;

static int ps_format;
static int old_h_option;

/* we only pretend to support this */
static int show_args;		/* implicit with -f and all BSD options */
static int bsd_c_option;	/* this option overrides the above */

static int ps_argc;		/* global argc */
static char **ps_argv;		/* global argv */
static int thisarg;		/* index into ps_argv */
static char *flagptr;		/* current location in ps_argv[thisarg] */

#ifndef HZ
#warning HZ not defined, assuming it is 100
#define HZ 100
#endif

int page_shift;			/* Page size as shift count */

static void usage(void)
{
	fprintf(stderr,
		"-C   select by command name (minimal ps only accepts one)\n"
		"-p   select by process ID (minimal ps only accepts one)\n"
		"-e   all processes (same as ax)\n"
		"a    all processes w/ tty, including other users\n"
		"x    processes w/o controlling ttys\n"
		"-f   full format\n"
		"-j,j job control format\n"
		"v    virtual memory format\n"
		"-l,l long format\n"
		"u    user-oriented format\n"
		"-o   user-defined format (limited support, only \"ps -o pid=\")\n"
		"h    no header\n"
/*
    "-A   all processes (same as ax)\n"
    "c    true command name\n"
    "-w,w wide output\n"
*/
	    );
	exit(1);
}

/*
 * Return the next argument, or call the usage function.
 * This handles both:   -oFOO   -o FOO
 */
static const char *get_opt_arg(void)
{
	const char *ret;
	ret = flagptr + 1;	/* assume argument is part of ps_argv[thisarg] */
	if (*ret)
		return ret;
	if (++thisarg >= ps_argc)
		usage();	/* there is nothing left */
	/* argument is the new ps_argv[thisarg] */
	ret = ps_argv[thisarg];
	if (!ret || !*ret)
		usage();
	return ret;
}

/* return the PID, or 0 if nothing good */
static void parse_pid(const char *str)
{
	char *endp;
	int num;
	if (!str)
		goto bad;
	num = strtol(str, &endp, 0);
	if (*endp != '\0')
		goto bad;
	if (num < 1)
		goto bad;
	if (want_one_pid)
		goto bad;
	want_one_pid = num;
	return;
      bad:
	usage();
}

/***************** parse SysV options, including Unix98  *****************/
static void parse_sysv_option(void)
{
	do {
		switch (*flagptr) {
    /**** selection ****/
		case 'C':	/* end */
			if (want_one_command)
				usage();
			want_one_command = get_opt_arg();
			return;	/* can't have any more options */
		case 'p':	/* end */
			parse_pid(get_opt_arg());
			return;	/* can't have any more options */
		case 'A':
		case 'e':
			select_all++;
			select_notty++;
		case 'w':	/* here for now, since the real one is not used */
			break;
    /**** output format ****/
		case 'f':
			show_args = 1;
			/* FALL THROUGH */
		case 'j':
		case 'l':
			if (ps_format)
				usage();
			ps_format = *flagptr;
			break;
		case 'o':	/* end */
			/* We only support a limited form: "ps -o pid="  (yes, just "pid=") */
			if (strcmp(get_opt_arg(), "pid="))
				usage();
			if (ps_format)
				usage();
			ps_format = 'o';
			old_h_option++;
			return;	/* can't have any more options */
    /**** other stuff ****/
#if 0
		case 'w':
			w_count++;
			break;
#endif
		default:
			usage();
		}		/* switch */
	} while (*++flagptr);
}

/************************* parse BSD options **********************/
static void parse_bsd_option(void)
{
	do {
		switch (*flagptr) {
    /**** selection ****/
		case 'a':
			select_all++;
			break;
		case 'x':
			select_notty++;
			break;
		case 'p':	/* end */
			parse_pid(get_opt_arg());
			return;	/* can't have any more options */
    /**** output format ****/
		case 'j':
		case 'l':
		case 'u':
		case 'v':
			if (ps_format)
				usage();
			ps_format = 0x80 | *flagptr;	/* use 0x80 to tell BSD from SysV */
			break;
    /**** other stuff ****/
		case 'c':
			bsd_c_option++;
#if 0
			break;
#endif
		case 'w':
#if 0
			w_count++;
#endif
			break;
		case 'h':
			old_h_option++;
			break;
		default:
			usage();
		}		/* switch */
	} while (*++flagptr);
}

#if 0
/* not used yet */
static void choose_dimensions(void)
{
	struct winsize ws;
	char *columns;
	/* screen_cols is 80 by default */
	if (ioctl(1, TIOCGWINSZ, &ws) != -1 && ws.ws_col > 30)
		screen_cols = ws.ws_col;
	columns = getenv("COLUMNS");
	if (columns && *columns) {
		long t;
		char *endptr;
		t = strtol(columns, &endptr, 0);
		if (!*endptr && (t > 30) && (t < (long)999999999))
			screen_cols = (int)t;
	}
	if (w_count && (screen_cols < 132))
		screen_cols = 132;
	if (w_count > 1)
		screen_cols = 999999999;
}
#endif

static void arg_parse(int argc, char *argv[])
{
	int sel = 0;		/* to verify option sanity */
	ps_argc = argc;
	ps_argv = argv;
	thisarg = 0;
  /**** iterate over the args ****/
	while (++thisarg < ps_argc) {
		flagptr = ps_argv[thisarg];
		switch (*flagptr) {
		case '0'...'9':
			show_args = 1;
			parse_pid(flagptr);
			break;
		case '-':
			flagptr++;
			parse_sysv_option();
			break;
		default:
			show_args = 1;
			parse_bsd_option();
			break;
		}
	}
  /**** sanity check and clean-up ****/
	if (want_one_pid)
		sel++;
	if (want_one_command)
		sel++;
	if (select_notty || select_all)
		sel++;
	if (sel > 1 || select_notty > 1 || select_all > 1 || bsd_c_option > 1
	    || old_h_option > 1)
		usage();
	if (bsd_c_option)
		show_args = 0;
}

/* return 1 if it works, or 0 for failure */
static int stat2proc(int pid)
{
	char buf[800];		/* about 40 fields, 64-bit decimal is about 20 chars */
	int num;
	int fd;
	char *tmp;
	struct stat sb;		/* stat() used to get EUID */

	snprintf(buf, 32, "/proc/%d/stat", pid);
	fd = open(buf, O_RDONLY, 0);
	if (fd == -1)
		return 0;
	num = read(fd, buf, sizeof buf - 1);
	fstat(fd, &sb);
	P_euid = sb.st_uid;
	close(fd);
	if (num < 80)
		return 0;
	buf[num] = '\0';
	tmp = strrchr(buf, ')');	/* split into "PID (cmd" and "<rest>" */
	*tmp = '\0';		/* replace trailing ')' with NUL */
	/* parse these two strings separately, skipping the leading "(". */
	memset(P_cmd, 0, sizeof P_cmd);	/* clear */
	sscanf(buf, "%d (%15c", &P_pid, P_cmd);	/* comm[16] in kernel */
	num = sscanf(tmp + 2,	/* skip space after ')' too */
		     "%c " "%d %d %d %d %d " "%lu %lu %lu %lu %lu %lu %lu " "%ld %ld %ld %ld %ld %ld " "%lu %lu " "%ld " "%lu %lu %lu %lu %lu %lu " "%u %u %u %u "	/* no use for RT signals */
		     "%lu %lu %lu",
		     &P_state,
		     &P_ppid, &P_pgrp, &P_session, &P_tty, &P_tpgid,
		     &P_flags, &P_min_flt, &P_cmin_flt, &P_maj_flt, &P_cmaj_flt,
		     &P_utime, &P_stime, &P_cutime, &P_cstime, &P_priority,
		     &P_nice, &P_timeout, &P_it_real_value, &P_start_time,
		     &P_vsize, &P_rss, &P_rss_rlim, &P_start_code, &P_end_code,
		     &P_start_stack, &P_kstk_esp, &P_kstk_eip, &P_signal,
		     &P_blocked, &P_sigignore, &P_sigcatch, &P_wchan, &P_nswap,
		     &P_cnswap);
/*    fprintf(stderr, "stat2proc converted %d fields.\n",num); */
	P_vsize /= 1024;
	P_rss <<= page_shift - 10;
	if (num < 30)
		return 0;
	if (P_pid != pid)
		return 0;
	return 1;
}

static const char *do_time(unsigned long t)
{
	int hh, mm, ss;
	static char buf[32];
	int cnt = 0;
	t /= HZ;
	ss = t % 60;
	t /= 60;
	mm = t % 60;
	t /= 60;
	hh = t % 24;
	t /= 24;
	if (t)
		cnt = snprintf(buf, sizeof buf, "%d-", (int)t);
	snprintf(cnt + buf, sizeof(buf) - cnt, "%02d:%02d:%02d", hh, mm, ss);
	return buf;
}

static void print_proc(void)
{
	char tty[16];
	snprintf(tty, sizeof tty, "%3d,%-3d", (P_tty >> 8) & 0xff,
		 P_tty & 0xff);
	switch (ps_format) {
	case 0:
		printf("%5d %s %s", P_pid, tty, do_time(P_utime + P_stime));
		break;
	case 'o':
		printf("%d\n", P_pid);
		return;		/* don't want the command */
	case 'l':
		printf("%03x %c %5d %5d %5d  - %3d %3d - "
		       "%5ld %06x %s %s",
		       (unsigned)P_flags & 0x777, P_state, P_euid, P_pid,
		       P_ppid, (int)P_priority, (int)P_nice,
		       P_vsize >> (page_shift - 10),
		       (unsigned)(P_wchan & 0xffffff), tty,
		       do_time(P_utime + P_stime)
		    );
		break;
	case 'f':
		printf("%5d %5d %5d  -   -   %s %s",
		       P_euid, P_pid, P_ppid, tty, do_time(P_utime + P_stime)
		    );
		break;
	case 'j':
		printf("%5d %5d %5d %s %s",
		       P_pid, P_pgrp, P_session, tty, do_time(P_utime + P_stime)
		    );
		break;
	case 'u' | 0x80:
		printf("%5d %5d    -    - %5ld %5ld %s %c   -   %s",
		       P_euid, P_pid, P_vsize, P_rss, tty, P_state,
		       do_time(P_utime + P_stime)
		    );
		break;
	case 'v' | 0x80:
		printf("%5d %s %c %s %6d   -   - %5d    -",
		       P_pid, tty, P_state, do_time(P_utime + P_stime),
		       (int)P_maj_flt, (int)P_rss);
		break;
	case 'j' | 0x80:
		printf("%5d %5d %5d %5d %s %5d %c %5d %s",
		       P_ppid, P_pid, P_pgrp, P_session, tty, P_tpgid, P_state,
		       P_euid, do_time(P_utime + P_stime)
		    );
		break;
	case 'l' | 0x80:
		printf("%03x %5d %5d %5d %3d %3d "
		       "%5ld %4ld %06x %c %s %s",
		       (unsigned)P_flags & 0x777, P_euid, P_pid, P_ppid,
		       (int)P_priority, (int)P_nice, P_vsize, P_rss,
		       (unsigned)(P_wchan & 0xffffff), P_state, tty,
		       do_time(P_utime + P_stime)
		    );
		break;
	default:
		break;
	}
	if (show_args)
		printf(" [%s]\n", P_cmd);
	else
		printf(" %s\n", P_cmd);
}

int main(int argc, char *argv[])
{
	arg_parse(argc, argv);

	page_shift = __getpageshift();

#if 0
	choose_dimensions();
#endif
	if (!old_h_option) {
		const char *head;
		switch (ps_format) {
		default:	/* can't happen */
		case 0:
			head = "  PID TTY         TIME CMD";
			break;
		case 'l':
			head =
			    "  F S   UID   PID  PPID  C PRI  NI ADDR SZ WCHAN    TTY       TIME CMD";
			break;
		case 'f':
			head =
			    "  UID   PID  PPID  C STIME   TTY       TIME CMD";
			break;
		case 'j':
			head = "  PID  PGID   SID TTY         TIME CMD";
			break;
		case 'u' | 0x80:
			head =
			    "  UID   PID %CPU %MEM   VSZ   RSS   TTY   S START     TIME COMMAND";
			break;
		case 'v' | 0x80:
			head =
			    "  PID   TTY   S     TIME  MAJFL TRS DRS   RSS %MEM COMMAND";
			break;
		case 'j' | 0x80:
			head =
			    " PPID   PID  PGID   SID   TTY   TPGID S   UID     TIME COMMAND";
			break;
		case 'l' | 0x80:
			head =
			    "  F   UID   PID  PPID PRI  NI   VSZ  RSS WCHAN  S   TTY       TIME COMMAND";
			break;
		}
		printf("%s\n", head);
	}
	if (want_one_pid) {
		if (stat2proc(want_one_pid))
			print_proc();
		else
			exit(1);
	} else {
		struct dirent *ent;	/* dirent handle */
		DIR *dir;
		int ouruid;
		int found_a_proc;
		found_a_proc = 0;
		ouruid = getuid();
		dir = opendir("/proc");
		if (!dir)
			exit(1);
		while ((ent = readdir(dir))) {
			if (*ent->d_name < '0' || *ent->d_name > '9')
				continue;
			if (!stat2proc(atoi(ent->d_name)))
				continue;
			if (want_one_command) {
				if (strcmp(want_one_command, P_cmd))
					continue;
			} else {
				if (!select_notty && P_tty == -1)
					continue;
				if (!select_all && P_euid != ouruid)
					continue;
			}
			found_a_proc++;
			print_proc();
		}
		closedir(dir);
		exit(!found_a_proc);
	}
	return 0;
}