Add basic sort logic.

[android-x86/external-toybox.git] / toys / posix / ps.c

/* ps.c - show process list
 *
 * Copyright 2015 Rob Landley <rob@landley.net>
 *
 * See http://pubs.opengroup.org/onlinepubs/9699919799/utilities/ps.html
 * And http://kernel.org/doc/Documentation/filesystems/proc.txt Table 1-4
 * And linux kernel source fs/proc/array.c function do_task_stat()
 *
 * Deviations from posix: no -n because /proc/self/wchan exists; we use -n to
 * mean "show numeric users and groups" instead.
 * Posix says default output should have field named "TTY" but if you "-o tty"
 * the same field should be called "TT" which is _INSANE_ and I'm not doing it.
 * Similarly -f outputs USER but calls it UID (we call it USER).
 * It also says that -o "args" and "comm" should behave differently but use
 * the same title, which is not the same title as the default output. (No.)
 * Select by session id is -s not -g.
 *
 * Posix defines -o ADDR as "The address of the process" but the process
 * start address is a constant on any elf system with mmu. The procps ADDR
 * field always prints "-" with an alignment of 1, which is why it has 11
 * characters left for "cmd" in in 80 column "ps -l" mode. On x86-64 you
 * need 12 chars, leaving nothing for cmd: I.E. posix 2008 ps -l mode can't
 * be sanely implemented on 64 bit Linux systems. In procps there's ps -y
 * which changes -l by removing the "F" column and swapping RSS for ADDR,
 * leaving 9 chars for cmd, so we're using that as our -l output.
 *
 * TODO: ps aux (att & bsd style "ps -ax" vs "ps ax" behavior difference)
 * TODO: finalize F, remove C
 *       switch -fl to -y, use "string" instead of constants to set, remove C
 * TODO: --sort
 * TODO: way too many hardwired constants here, how can I generate them?
 * TODO: thread support /proc/$d/task/%d/stat (and -o stat has "l")
 *
 * Design issue: the -o fields are an ordered array, and the order is
 * significant. The array index is used in strawberry->which (consumed
 * in do_ps()) and in the bitmasks enabling default fields in ps_main().

USE_PS(NEWTOY(ps, "k(sort)P(ppid)*aAdeflno*p(pid)*s*t*u*U*g*G*wZ[!ol][+Ae]", TOYFLAG_USR|TOYFLAG_BIN))

config PS
  bool "ps"
  default y
  help
    usage: ps [-AadeflnwZ] [-gG GROUP,] [-k FIELD,] [-o FIELD,] [-p PID,] [-t TTY,] [-uU USER,]

    List processes.

    Which processes to show (selections may be comma separated lists):

    -A  All processes
    -a  Processes with terminals that aren't session leaders
    -d  All processes that aren't session leaders
    -e  Same as -A
    -g  Belonging to GROUPs
    -G  Belonging to real GROUPs (before sgid)
    -p  PIDs (--pid)
    -P  Parent PIDs (--ppid)
    -s  In session IDs
    -t  Attached to selected TTYs
    -u  Owned by USERs
    -U  Owned by real USERs (before suid)

    Output modifiers:

    -k  Sort FIELDs in +increasing or -decreasting order (--sort)
    -n  Show numeric USER and GROUP
    -w  Wide output (don't truncate at terminal width)

    Which FIELDs to show. (Default = -o PID,TTY,TIME,CMD)

    -f  Full listing (-o USER:8=UID,PID,PPID,C,STIME,TTY,TIME,CMD)
    -l  Long listing (-o F,S,UID,PID,PPID,C,PRI,NI,ADDR,SZ,WCHAN,TTY,TIME,CMD)
    -o  Output the listed FIELDs, each with optional :size and/or =title
    -Z  Include LABEL

    Available -o FIELDs:

      ADDR    Instruction pointer
      CMD     Command name (original)
      CMDLINE Command name (current argv[0])
      COMM    Command line (with arguments)
      ETIME   Elapsed time since process start
      F       Process flags (PF_*) from linux source file include/sched.h
              (in octal rather than hex because posix)
      GID     Group id
      GROUP   Group name
      LABEL   Security label
      MAJFL   Major page faults
      MINFL   Minor page faults
      NI      Niceness of process (lower niceness is higher priority)
      PCPU    Percentage of CPU time used
      PGID    Process Group ID
      PID     Process ID
      PPID    Parent Process ID
      PRI     Priority
      RGID    Real (before sgid) group ID
      RGROUP  Real (before sgid) group name
      RSS     Resident Set Size (memory currently used)
      RUID    Real (before suid) user ID
      RUSER   Real (before suid) user name
      S       Process state:
              R (running) S (sleeping) D (disk sleep) T (stopped)  t (traced)
              Z (zombie)  X (dead)     x (dead)       K (wakekill) W (waking)
      STAT    Process state (S) plus:
              < high priority          N low priority L locked memory
              s session leader         + foreground   l multithreaded
      STIME   Start time of process in hh:mm (size :19 shows yyyy-mm-dd hh:mm:ss)
      SZ      Memory Size (4k pages needed to completely swap out process)
      TIME    CPU time consumed
      TTY     Controlling terminal
      UID     User id
      USER    User name
      VSZ     Virtual memory size (1k units)
      WCHAN   Waiting in kernel for
*/

#define FOR_ps
#include "toys.h"

GLOBALS(
  struct arg_list *G;
  struct arg_list *g;
  struct arg_list *U;
  struct arg_list *u;
  struct arg_list *t;
  struct arg_list *s;
  struct arg_list *p;
  struct arg_list *o;
  struct arg_list *P;
  struct arg_list *k;

  struct ptr_len gg, GG, pp, PP, ss, tt, uu, UU, *parsing;
  unsigned width;
  dev_t tty;
  void *fields;
  long long ticks, bits;
  size_t header_len;
  int kcount;
)

struct strawberry {
  struct strawberry *next, *prev;
  short which, len;
  char *title;
  char forever[];
};

// Data layout in toybuf
struct carveup {
  long long slot[50];       // data from /proc, skippint #2 and #3
  unsigned short offset[4]; // offset of fields in str[] (skip name, always 0)
  char state;
  char str[];              // name, tty, wchan, attr, cmdline
};

// Return 1 to keep, 0 to discard
static int match_process(long long *slot)
{
  struct ptr_len *match[] = {
    &TT.gg, &TT.GG, &TT.pp, &TT.PP, &TT.ss, &TT.tt, &TT.uu, &TT.UU
  };
  int i, j, mslot[] = {33, 34, 0, 1, 3, 4, 31, 32};
  long *ll = 0;

  // Do we have -g -G -p -P -s -t -u -U options selecting processes?
  for (i = 0; i < ARRAY_LEN(match); i++) {
    if (match[i]->len) {
      ll = match[i]->ptr;
      for (j = 0; j<match[i]->len; j++) if (ll[j] == slot[mslot[i]]) return 1;
    }
  }

  // If we had selections and didn't match them, don't display
  if (ll) return 0;

  // Filter implicit categories for other display types
  if ((toys.optflags&(FLAG_a|FLAG_d)) && slot[3]==*slot) return 0;
  if ((toys.optflags&FLAG_a) && !slot[4]) return 0;
  if (!(toys.optflags&(FLAG_a|FLAG_d|FLAG_A|FLAG_e)) && TT.tty!=slot[4])
    return 0;

  return 1;
}

static char *string_field(struct carveup *tb, struct strawberry *field)
{
  char *buf = toybuf+sizeof(toybuf)-64, *out = buf, *s;
  long long ll, *slot = tb->slot;
  int i;

  // Default: unsupported (5 "C")
  sprintf(out, "-");

  // stat#s: PID, PPID, PRI, NI, ADDR, SZ, RSS, PGID, VSS, MAJFL, MINFL
  if (-1!=(i = stridx((char[]){3,4,6,7,8,9,24,19,23,25,30,0}, field->which)))
  {
    char *fmt = "%lld";

    ll = slot[((char[]){0,1,15,16,27,20,21,2,20,9,7})[i]];
    if (i==2) ll--;
    if (i==4) fmt = "%llx";
    else if (i==5) ll >>= 12;
    else if (i==6) ll <<= 2;
    else if (i==8) ll >>= 10;
    sprintf(out, fmt, ll);
  // user/group: UID USER RUID RUSER GID GROUP RGID RGROUP
  } else if (-1!=(i = stridx((char[]){2,22,28,21,26,17,29,20}, field->which)))
  {
    int id = slot[31+i/2]; // uid, ruid, gid, rgid

    // Even entries are numbers, odd are names
    sprintf(out, "%d", id);
    if (!(toys.optflags&FLAG_n) && i&1) {
      if (i>3) {
        struct group *gr = getgrgid(id);

        if (gr) out = gr->gr_name;
      } else {
        struct passwd *pw = getpwuid(id);

        if (pw) out = pw->pw_name;
      }
    }
  // CMD TTY WCHAN LABEL (CMDLINE handled elsewhere)
  } else if (-1!=(i = stridx((char[]){15,12,10,31}, field->which))) {
    out = tb->str;
    if (i) out += tb->offset[i-1];

  // F (also assignment of i used by later tests)
  // Posix doesn't specify what flags should say. Man page says
  // 1 for PF_FORKNOEXEC and 4 for PF_SUPERPRIV from linux/sched.h
  } else if (!(i = field->which)) sprintf(out, "%llo", (slot[6]>>6)&5);
  // S STAT
  else if (i==1 || i==27) {
    s = out;
    *s++ = tb->state;
    if (i==27) {
      // TODO l = multithreaded
      if (slot[16]<0) *s++ = '<';
      else if (slot[16]>0) *s++ = 'N';
      if (slot[3]==*slot) *s++ = 's';
      if (slot[18]) *s++ = 'L';
      if (slot[5]==*slot) *s++ = '+';
    } 
    *s = 0;
  // STIME
  } else if (i==11) {
    time_t t = time(0)-slot[46]+slot[19]/sysconf(_SC_CLK_TCK);

    // Padding behavior's a bit odd: default field size is just hh:mm.
    // Increasing stime:size reveals more data at left until full,
    // so move start address so yyyy-mm-dd hh:mm revealed on left at :16,
    // then add :ss on right for :19.
    strftime(out, 64, "%F %T", localtime(&t));
    out = out+strlen(out)-3-abs(field->len);
    if (out<buf) out = buf;

  // TIME ELAPSED
  } else if (i==13 || i==16) {
    int unit = 60*60*24, j = sysconf(_SC_CLK_TCK);
    time_t seconds = (i==16) ? (slot[46]*j)-slot[19] : slot[11]+slot[12];

    seconds /= j;
    for (s = 0, j = 0; j<4; j++) {
      // TIME has 3 required fields, ETIME has 2. (Posix!)
      if (!s && (seconds>unit || j == 1+(i==16))) s = out;
      if (s) {
        s += sprintf(s, j ? "%02ld": "%2ld", (long)(seconds/unit));
        if ((*s = "-::"[j])) s++;
      }
      seconds %= unit;
      unit /= j ? 60 : 24;
    }

  // COMM - command line including arguments
  // CMDLINE - command name from /proc/pid/cmdline (no arguments)
  } else if (i==14 || i==32) {
    if (slot[47]<1) {
      out = toybuf+sizeof(toybuf)-300;
      sprintf(out, "[%s]", tb->str); // kernel thread, use real name
    } else {
      out = tb->str+tb->offset[3];
      if (slot[47]!=INT_MAX) out[slot[47]] = ' '*(i==14);
    }

  // %CPU
  } else if (i==18) {
    ll = (slot[46]*sysconf(_SC_CLK_TCK)-slot[19]);
    i = ((slot[11]+slot[12])*1000)/ll;
    sprintf(out, "%d.%d", i/10, i%10);
  }

  return out;
}

// Display process data that get_ps() read from /proc, formatting with TT.fields
static void show_ps(struct carveup *tb)
{
  struct strawberry *field;
  int i, len, width = TT.width;

  // Loop through fields to display
  for (field = TT.fields; field; field = field->next) {
    char *out = string_field(tb, field);

    // Output the field, appropriately padded
    len = width - (field != TT.fields);
    if (!field->next && field->len<0) i = 0;
    else {
      i = len<abs(field->len) ? len : field->len;
      len = abs(i);
    }

    // TODO test utf8 fontmetrics
    width -= printf(" %*.*s" + (field == TT.fields), i, len, out);
    if (!width) break;
  }
  xputc('\n');
}

// dirtree callback: read data about process to display, store, or discard it.
// Collects slot[50] plus  stat, name, tty, wchan, attr, cmdline
static int get_ps(struct dirtree *new)
{
  struct {
    char *name;
    long long bits;
  } fetch[] = {{"fd/", 1<<12}, {"wchan", 1<<10}, {"attr/current", 1<<31},
               {"cmdline", (1<<14)|(1LL<<32)}};
  struct carveup *tb = (void *)toybuf;
  long long *slot = (void *)toybuf;
  char *name, *s, *buf = tb->str, *end = 0;
  int i, j, fd, ksave = DIRTREE_SAVE*!!(toys.optflags&FLAG_k);
  off_t len;

  // Recurse one level into /proc children, skip non-numeric entries
  if (!new->parent) return DIRTREE_RECURSE|DIRTREE_SHUTUP|ksave;
  if (!(*slot = atol(new->name))) return 0;
  fd = dirtree_parentfd(new);

  len = 2048;
  sprintf(buf, "%lld/stat", *slot);
  if (!readfileat(fd, buf, buf, &len)) return 0;

  // parse oddball fields (name and state). Name can have embedded ')' so match
  // _last_ ')' in stat (although VFS limits filenames to 255 bytes max).
  // All remaining fields should be numeric.
  if (!(name = strchr(buf, '('))) return 0;
  for (s = ++name; *s; s++) if (*s == ')') end = s;
  if (!end || end-name>255) return 0;

  // Move name right after slot[] array (pid already set, so stomping it's ok)
  // and convert low chars to spaces while we're at it.
  for (i = 0; i<end-name; i++)
    if ((tb->str[i] = name[i]) < ' ') tb->str[i] = ' ';
  buf = tb->str+i;
  *buf++ = 0;

  // Parse numeric fields (starting at 4th field in slot[1])
  if (1>sscanf(s = end, ") %c%n", &tb->state, &i)) return 0;
  for (j = 1; j<50; j++) if (1>sscanf(s += i, " %lld%n", slot+j, &i)) break;

  // Now we've read the data, move status and name right after slot[] array,
  // and convert low chars to spaces while we're at it.
  for (i = 0; i<end-name; i++)
    if ((tb->str[i] = name[i]) < ' ') tb->str[i] = ' ';
  buf = tb->str+i;
  *buf++ = 0;

  // save uid, ruid, gid, gid, and rgid int slots 31-34 (we don't use sigcatch
  // or numeric wchan, and the remaining two are always zero), and vmlck into
  // 18 (which is "obsolete, always 0")
  slot[31] = new->st.st_uid;
  slot[33] = new->st.st_gid;

  // If RGROUP RUSER STAT RUID RGID happening, or -G or -U, parse "status"
  // Save ruid in slot[34] and rgid in slot[35], which are otherwise zero,
  // and vmlck into slot[18] (it_real_value, also always zero).
  if ((TT.bits & 0x38300000) || TT.GG.len || TT.UU.len) {
    len = sizeof(toybuf)-(buf-toybuf);
    sprintf(buf, "%lld/status", *slot);
    if (!readfileat(fd, buf, buf, &len)) *buf = 0;
    s = strstr(buf, "\nUid:");
    slot[32] = s ? atol(s+5) : new->st.st_uid;
    s = strstr(buf, "\nGid:");
    slot[34] = s ? atol(s+5) : new->st.st_gid;
    s = strstr(buf, "\nVmLck:");
    if (s) slot[18] = atoll(s+5);
  }

  // We now know enough to skip processes we don't care about.
  if (!match_process(slot)) return 0;

  // /proc data is generated as it's read, so for maximum accuracy on slow
  // systems (or ps | more) we re-fetch uptime as we fetch each /proc line.
  sysinfo((void *)(toybuf+2048));
  slot[46] = ((struct sysinfo *)toybuf)->uptime;

  // fetch remaining data while parentfd still available, appending to buf.
  // (There's well over 3k of toybuf left. We could dynamically malloc, but
  // it'd almost never get used, querying length of a proc file is awkward,
  // fixed buffer is nommu friendly... Wait for somebody to complain. :)
  for (j = 0; j<ARRAY_LEN(fetch); j++) { 
    tb->offset[j] = buf-(tb->str);
    if (!(TT.bits&fetch[j].bits)) {
      *buf++ = 0;
      continue;
    }

    // Determine remaining space, reserving minimum of 256 bytes/field and
    // 64 bytes scratch space at the end (for output conversion later).
    len = sizeof(toybuf)-(buf-toybuf)-64-256*(ARRAY_LEN(fetch)-j);
    sprintf(buf, "%lld/%s", *slot, fetch[j].name);

    // If it's not the TTY field, data we want is in a file.
    // Last length saved in slot[] is command line (which has embedded NULs)
    if (j) {
      readfileat(fd, buf, buf, &len);

      // When command has no arguments, don't space over the NUL
      if (len>0) {
        int temp = 0;

        if (buf[len-1]=='\n') buf[--len] = 0;

        // Always escape spaces because an executable named esc[0m would be bad.
        // Escaping low ascii does not affect utf8.
        for (i=0; i<len; i++) {
          if (!temp && !buf[i]) temp = i;
          if (buf[i]<' ') buf[i] = ' ';
        }
        if (temp) len = temp; // position of _first_ NUL
        else len = INT_MAX;
      } else *buf = len = 0;
      // Store end of argv[0] so COMM and CMDLINE can differ.
      slot[47] = len;
    } else {
      int rdev = slot[4];
      struct stat st;

      // Call no tty "?" rather than "0:0".
      strcpy(buf, "?");
      if (rdev) {
        // Can we readlink() our way to a name?
        for (i = 0; i<3; i++) {
          sprintf(buf, "%lld/fd/%i", *slot, i);
          if (!fstatat(fd, buf, &st, 0) && S_ISCHR(st.st_mode)
            && st.st_rdev == rdev && 0<(len = readlinkat(fd, buf, buf, len)))
          {
            buf[len] = 0;
            break;
          }
        }

        // Couldn't find it, try all the tty drivers.
        if (i == 3) {
          FILE *fp = fopen("/proc/tty/drivers", "r");
          int tty_major = 0, maj = major(rdev), min = minor(rdev);

          if (fp) {
            while (fscanf(fp, "%*s %256s %d %*s %*s", buf, &tty_major) == 2) {
              // TODO: we could parse the minor range too.
              if (tty_major == maj) {
                sprintf(buf+strlen(buf), "%d", min);
                if (!stat(buf, &st) && S_ISCHR(st.st_mode) && st.st_rdev==rdev)
                  break;
              }
              tty_major = 0;
            }
            fclose(fp);
          }

          // Really couldn't find it, so just show major:minor.
          if (!tty_major) sprintf(buf, "%d:%d", maj, min);
        }

        s = buf;
        if (strstart(&s, "/dev/")) memmove(buf, s, strlen(s)+1);;
      }
    }
    buf += strlen(buf)+1;
  }

  // If we need to sort the output, add it to the list and return.
  if (ksave) {
    s = xmalloc(buf-toybuf);
    new->extra = (long)s;
    memcpy(s, toybuf, buf-toybuf);
    TT.kcount++;

  // Otherwise display it now
  } else show_ps(tb);

  return ksave;
}

// Traverse arg_list of csv, calling callback on each value
void comma_args(struct arg_list *al, char *err,
  char *(*callback)(char *str, int len))
{
  char *next, *arg;
  int len;

  while (al) {
    arg = al->arg;
    while ((next = comma_iterate(&arg, &len)))
      if ((next = callback(next, len)))
        perror_exit("%s '%s'\n%*c", err, al->arg,
          (int)(5+strlen(toys.which->name)+strlen(err)+next-al->arg), '^');
    al = al->next;
  }
}

static char *parse_o(char *type, int length)
{
  struct strawberry *field;
  char *width, *title, *end, *s, *typos[] = {
         "F", "S", "UID", "PID", "PPID", "C", "PRI", "NI", "ADDR", "SZ",
         "WCHAN", "STIME", "TTY", "TIME", "CMD", "COMMAND", "ELAPSED", "GROUP",
         "%CPU", "PGID", "RGROUP", "RUSER", "USER", "VSZ", "RSS", "MAJFL",
         "GID", "STAT", "RUID", "RGID", "MINFL", "LABEL", "CMDLINE"
  };
  // TODO: Android uses -30 for LABEL, but ideally it would auto-size.
  signed char widths[] = {1,-1,5,5,5,2,3,3,4+sizeof(long),5,
                          -6,5,-8,8,-27,-27,11,-8,
                          4,5,-8,-8,-8,6,5,6,
                          8,-5,4,4,6,-30,-27};
  int i, j, k;

  // Get title, length of title, type, end of type, and display width

  // Chip off =name to display
  if ((end = strchr(type, '=')) && length>(end-type)) {
    title = end+1;
    length -= (end-type)+1;
  } else {
    end = type+length;
    title = 0;
  }

  // Chip off :width to display
  if ((width = strchr(type, ':')) && width<end) {
    if (!title) length = width-type;
  } else width = 0;

  // Allocate structure, copy title
  field = xzalloc(sizeof(struct strawberry)+(length+1)*!!title);
  if (title) {
    memcpy(field->title = field->forever, title, length);
    field->title[field->len = length] = 0;
  }

  if (width) {
    field->len = strtol(++width, &title, 10);
    if (!isdigit(*width) || title != end) return title;
    end = --width;
  }

  // Find type
  for (i = 0; i<ARRAY_LEN(typos); i++) {
    field->which = i;
    for (j = 0; j<2; j++) {
      if (!j) s = typos[i];
      // posix requires alternate names for some fields
      else if (-1==(k = stridx((char []){7,14,15,16,18,23,22,0}, i))) continue;
      else s = ((char *[]){"NICE","ARGS","COMM","ETIME","PCPU",
                           "VSIZE","UNAME"})[k];

      if (!strncasecmp(type, s, end-type) && strlen(s)==end-type) break;
    }
    if (j!=2) break;
  }
  if (i==ARRAY_LEN(typos)) return type;
  if (!field->title) field->title = typos[field->which];
  if (!field->len) field->len = widths[field->which];
  else if (widths[field->which]<0) field->len *= -1;
  dlist_add_nomalloc((void *)&TT.fields, (void *)field);

  // Print padded header.
  TT.header_len +=
    snprintf(toybuf + TT.header_len, sizeof(toybuf) - TT.header_len,
             " %*s" + (field == TT.fields), field->len, field->title);
  TT.bits |= (i = 1<<field->which);

  return 0;
}

// Parse -p -s -t -u -U -g -G
static char *parse_rest(char *str, int len)
{
  struct ptr_len *pl = TT.parsing;
  long *ll = pl->ptr;
  char *end;
  int num = 0;

  // numeric: -p, -s
  // gg, GG, pp, ss, tt, uu, UU, *parsing;
 
  // Allocate next chunk of data
  if (!(15&pl->len))
    ll = pl->ptr = xrealloc(pl->ptr, sizeof(long)*(pl->len+16));

  // Parse numerical input
  if (isdigit(*str)) {
    ll[pl->len] = xstrtol(str, &end, 10);
    if (end==(len+str)) num++;
  }

  if (pl==&TT.pp || pl==&TT.ss) {
    if (num && ll[pl->len]>0) {
      pl->len++;

      return 0;
    }
  } else if (pl==&TT.tt) {
    // -t pts = 12,pts/12 tty = /dev/tty2,tty2,S0
    if (!num) {
      if (strstart(&str, strcpy(toybuf, "/dev/"))) len -= 5;
      if (strstart(&str, "pts/")) {
        len -= 4;
        num++;
      } else if (strstart(&str, "tty")) len -= 3;
    }
    if (len<256 && (!(end = strchr(str, '/')) || end-str>len)) {
      struct stat st;

      end = toybuf + sprintf(toybuf, "/dev/%s", num ? "pts/" : "tty");
      memcpy(end, str, len);
      end[len] = 0;
      xstat(toybuf, &st);
      ll[pl->len++] = st.st_rdev;

      return 0;
    }
  } else if (len<255) {
    char name[256];

    if (num) {
      pl->len++;

      return 0;
    }

    memcpy(name, str, len);
    name[len] = 0;
    if (pl==&TT.gg || pl==&TT.GG) {
      struct group *gr = getgrnam(name);
      if (gr) {
        ll[pl->len++] = gr->gr_gid;

        return 0;
      }
    } else if (pl==&TT.uu || pl==&TT.UU) {
      struct passwd *pw = getpwnam(name);
      if (pw) {
        ll[pl->len++] = pw->pw_uid;

        return 0;
      }
    }
  }

  // Return error
  return str;
}

// sort for -k
static int ksort(void *aa, void *bb)
{
  long long lla, llb;
  char *out, *end;

  // Convert fields to string version, saving first in toybuf
  out = string_field((void *)aa, TT.fields);
  memccpy(toybuf, out, 0, 2048);
  toybuf[2048] = 0;
  out = string_field((void *)bb, TT.fields);

  // Numeric comparison?
  llb = strtoll(out, &end, 10);
  if (!*end) {
    lla = strtoll(toybuf, &end, 10);
    if (!*end) {
      if (lla<llb) return -1;
      if (lla>llb) return 1;
      return 0;
    }
  }

  // String compare
  return strcmp(toybuf, out);
}

void ps_main(void)
{
  struct dirtree *dt;
  int i;

  TT.width = 99999;
  if (!(toys.optflags&FLAG_w)) terminal_size(&TT.width, 0);

  // find controlling tty, falling back to /dev/tty if none
  for (i = 0; !TT.tty && i<4; i++) {
    struct stat st;
    int fd = i;

    if (i==3 && -1==(fd = open("/dev/tty", O_RDONLY))) break;

    if (isatty(fd) && !fstat(fd, &st)) TT.tty = st.st_rdev;
    if (i==3) close(fd);
  }

  // parse command line options other than -o
  TT.parsing = &TT.PP;
  comma_args(TT.P, "bad -P", parse_rest);
  TT.parsing = &TT.pp;
  comma_args(TT.p, "bad -p", parse_rest);
  TT.parsing = &TT.tt;
  comma_args(TT.t, "bad -t", parse_rest);
  TT.parsing = &TT.ss;
  comma_args(TT.s, "bad -s", parse_rest);
  TT.parsing = &TT.uu;
  comma_args(TT.u, "bad -u", parse_rest);
  TT.parsing = &TT.UU;
  comma_args(TT.U, "bad -u", parse_rest);
  TT.parsing = &TT.gg;
  comma_args(TT.g, "bad -g", parse_rest);
  TT.parsing = &TT.GG;
  comma_args(TT.G, "bad -G", parse_rest);

  // Parse manual field selection, or default/-f/-l, plus -Z,
  // constructing the header line in toybuf as we go.
  if (toys.optflags&FLAG_Z) {
    struct arg_list Z = { 0, "LABEL" };

    comma_args(&Z, "-Z", parse_o);
  }
  if (TT.o) comma_args(TT.o, "bad -o field", parse_o);
  else {
    struct arg_list al;

    al.next = 0;
    if (toys.optflags&FLAG_f)
      al.arg = "USER:8=UID,PID,PPID,C,STIME,TTY,TIME,CMD";
    else if (toys.optflags&FLAG_l)
      al.arg = "F,S,UID,PID,PPID,C,PRI,NI,ADDR,SZ,WCHAN,TTY,TIME,CMD";
    else if (CFG_TOYBOX_ON_ANDROID)
      al.arg = "USER,PID,PPID,VSIZE,RSS,WCHAN:10,ADDR:10=PC,S,CMDLINE";
    else al.arg = "PID,TTY,TIME,CMD";

    comma_args(&al, 0, parse_o);
  }
  dlist_terminate(TT.fields);
  printf("%s\n", toybuf);

  dt = dirtree_read("/proc", get_ps);

  if (toys.optflags&FLAG_k) {
    struct carveup **tbsort = xmalloc(TT.kcount*sizeof(struct carveup *));

    // descend into child list
    *tbsort = (void *)dt;
    dt = dt->child;
    free(*tbsort);

    // populate array
    i = 0;
    while (dt) {
      void *temp = dt->next;

      tbsort[i++] = (void *)dt->extra;
      free(dt);
      dt = temp;
    }

    qsort(tbsort, TT.kcount, sizeof(struct dirtree *), (void *)ksort);
    for (i = 0; i<TT.kcount; i++) {
      show_ps(tbsort[i]);
      free(tbsort[i]);
    }
  }

  if (CFG_TOYBOX_FREE) {
    free(TT.gg.ptr);
    free(TT.GG.ptr);
    free(TT.pp.ptr);
    free(TT.PP.ptr);
    free(TT.ss.ptr);
    free(TT.tt.ptr);
    free(TT.uu.ptr);
    free(TT.UU.ptr);
    llist_traverse(TT.fields, free);
  }
}