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tail.c

/***********************************************************************
*                                                                      *
*               This software is part of the ast package               *
*                  Copyright (c) 1992-2005 AT&T Corp.                  *
*                      and is licensed under the                       *
*                  Common Public License, Version 1.0                  *
*                            by AT&T Corp.                             *
*                                                                      *
*                A copy of the License is available at                 *
*            http://www.opensource.org/licenses/cpl1.0.txt             *
*         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
*                                                                      *
*              Information and Software Systems Research               *
*                            AT&T Research                             *
*                           Florham Park NJ                            *
*                                                                      *
*                 Glenn Fowler <gsf@research.att.com>                  *
*                  David Korn <dgk@research.att.com>                   *
*                                                                      *
***********************************************************************/
#pragma prototyped

/*
 * print the tail of one or more files
 *
 *   David Korn
 *   Glenn Fowler
 */

static const char usage[] =
"+[-?\n@(#)$Id: tail (AT&T Labs Research) 2004-10-31 $\n]"
USAGE_LICENSE
"[+NAME?tail - output trailing portion of one or more files ]"
"[+DESCRIPTION?\btail\b copies one or more input files to standard output "
      "starting at a designated point for each file.  Copying starts "
      "at the point indicated by the options and is unlimited in size.]"
"[+?By default a header of the form \b==> \b\afilename\a\b <==\b "
      "is output before all but the first file but this can be changed "
      "with the \b-q\b and \b-v\b options.]"
"[+?If no \afile\a is given, or if the \afile\a is \b-\b, \btail\b "
      "copies from standard input. The start of the file is defined "
      "as the current offset.]"
"[+?The option argument for \b-c\b can optionally be "
      "followed by one of the following characters to specify a different "
      "unit other than a single byte:]{"
            "[+b?512 bytes.]"
            "[+k?1-kilobyte.]"
            "[+m?1-megabyte.]"
      "}"
"[+?For backwards compatibility, \b-\b\anumber\a  is equivalent to "
      "\b-n\b \anumber\a and \b+\b\anumber\a is equivalent to "
      "\b-n -\b\anumber\a.]"

"[n:lines]:[lines:=10?Copy \alines\a lines from each file.  A negative value "
      "for \alines\a indicates an offset from the start of the file.]"
"[c:bytes]:[chars?Copy \achars\a bytes from each file.  A negative value "
      "for \achars\a indicates an offset from the start of the file.]"
"[f:forever|follow?Loop forever trying to read more characters as the "
      "end of each file to copy new data. Ignored if reading from a pipe "
      "or fifo.]"
"[h!:headers?Output filename headers.]"
"[l:log?When a \b--forever\b file times out via \b--timeout\b, verify that "
      "the curent file has not been renamed and replaced by another file "
      "of the same name (a common log file practice) before giving up on "
      "the file.]"
"[q:quiet?Don't output filename headers. For GNU compatibility.]"
"[r:reverse?Output lines in reverse order.]"
"[s:silent?Don't warn about timeout expiration and log file changes.]"
"[t:timeout?Stop checking after \atimeout\a elapses with no additional "
      "\b--forever\b output. A separate elapsed time is maintained for "
      "each file operand. There is no timeout by default. The default "
      "\atimeout\a unit is seconds. \atimeout\a may be a catenation of 1 "
      "or more integers, each followed by a 1 character suffix. The suffix "
      "may be omitted from the last integer, in which case it is "
      "interpreted as seconds. The supported suffixes are:]:[timeout]{"
            "[+s?seconds]"
            "[+m?minutes]"
            "[+h?hours]"
            "[+d?days]"
            "[+w?weeks]"
            "[+M?months]"
            "[+y?years]"
            "[+S?scores]"
      "}"
"[v:verbose?Always ouput filename headers.]"
"\n"
"\n[file ...]\n"
"\n"
"[+EXIT STATUS?]{"
      "[+0?All files copied successfully.]"
      "[+>0?One or more files did not copy.]"
"}"
"[+SEE ALSO?\bcat\b(1), \bhead\b(1), \brev\b(1)]"
;

#include <cmdlib.h>
#include <ctype.h>
#include <ls.h>
#include <tm.h>

#define COUNT           (1<<0)
#define FOLLOW          (1<<1)
#define HEADERS         (1<<2)
#define LOG       (1<<3)
#define REVERSE         (1<<4)
#define SILENT          (1<<5)
#define TIMEOUT         (1<<6)
#define VERBOSE         (1<<7)

#define NOW       (unsigned long)time(NiL)

struct Tail_s; typedef struct Tail_s Tail_t;

struct Tail_s
{
      Tail_t*           next;
      char*       name;
      Sfio_t*           sp;
      Sfoff_t           size;
      Sfoff_t           last;
      unsigned long     expire;
      long        dev;
      long        ino;
};

/*
 * if file is seekable, position file to tail location and return offset
 * otherwise, return -1
 */

static Sfoff_t
tailpos(register Sfio_t* fp, register long nitems, int delim)
{
      register size_t         n;
      register Sfoff_t  offset;
      register Sfoff_t  first;
      register Sfoff_t  last;
      register char*          s;
      register char*          t;

      if ((first = sfseek(fp, (Sfoff_t)0, SEEK_CUR)) < 0)
            return -1;
      last = sfsize(fp);
      if (delim < 0)
      {
            if ((offset = last - nitems) < first)
                  return first;
            return offset;
      }
      if ((offset = last - SF_BUFSIZE) < first)
            offset = first;
      for (;;)
      {
            sfseek(fp, offset, SEEK_SET);
            n = last - offset;
            if (!(s = sfreserve(fp, n, SF_LOCKR)))
                  return -1;
            t = s + n;
            while (t > s)
                  if (*--t == delim && nitems-- <= 0)
                  {
                        sfread(fp, s, 0);
                        return offset + (t - s) + 1;
                  }
            sfread(fp, s, 0);
            if (offset == first)
                  break;
            last = offset;
            if ((offset = last - SF_BUFSIZE) < first)
                  offset = first;
      }
      return first;
}

/*
 * this code handles tail from a pipe without any size limits
 */

static void
pipetail(Sfio_t* infile, Sfio_t* outfile, int nitems, int delim)
{
      register Sfio_t*  out;
      register int            n = (2 * SF_BUFSIZE);
      register int            nleft = nitems;
      register int            fno = 0;
      Sfoff_t                 offset[2];
      Sfio_t*                 tmp[2];

      if (delim < 0 && nitems < n)
            n = nitems;
      out = tmp[0] = sftmp(n);
      tmp[1] = sftmp(n);
      offset[0] = offset[1] = 0;
      while ((n = sfmove(infile, out, nleft, delim)) > 0)
      {
            offset[fno] = sftell(out);
            if ((nleft -= n) <= 0)
            {
                  out = tmp[fno= !fno];
                  sfseek(out, (Sfoff_t)0, SEEK_SET);
                  nleft = nitems;
            }
      }
      if (nleft == nitems)
      {
            offset[fno] = 0;
            fno= !fno;
      }
      sfseek(tmp[0], (Sfoff_t)0, SEEK_SET);

      /*
       * see whether both files are needed
       */

      if (offset[fno])
      {
            sfseek(tmp[1], (Sfoff_t)0, SEEK_SET);
            if ((n = nitems - nleft) > 0) 
                  sfmove(tmp[!fno], NiL, n, delim); 
            if ((n = offset[!fno] - sftell(tmp[!fno])) > 0)
                  sfmove(tmp[!fno], outfile, n, -1); 
      }
      else
            fno = !fno;
      sfmove(tmp[fno], outfile, offset[fno], -1); 
      sfclose(tmp[0]);
      sfclose(tmp[1]);
}

/*
 * (re)initialize a tail stream
 */

static int
init(Tail_t* tp, long number, int delim, int flags)
{
      Sfoff_t           offset;
      struct stat st;

      if (tp->sp)
      {
            offset = 0;
            if (tp->sp == sfstdin)
                  tp->sp = 0;
      }
      else
            offset = 1;
      if (streq(tp->name, "-"))
            tp->sp = sfstdin;
      else if (!(tp->sp = sfopen(tp->sp, tp->name, "r")))
      {
            error(ERROR_system(0), "%s: cannot open", tp->name);
            return -1;
      }
      sfset(tp->sp, SF_SHARE, 0);
      tp->last = 0;
      if (offset)
      {
            if ((offset = tailpos(tp->sp, number, delim)) < 0)
            {
                  error(ERROR_SYSTEM|2, "%s: cannot position file to tail", tp->name);
                  goto bad;
            }
            sfseek(tp->sp, offset, SEEK_SET);
      }
      tp->size = offset;
      if (flags & LOG)
      {
            if (fstat(sffileno(tp->sp), &st))
            {
                  error(ERROR_system(0), "%s: cannot stat", tp->name);
                  goto bad;
            }
            tp->dev = st.st_dev;
            tp->ino = st.st_ino;
      }
      return 0;
 bad:
      if (tp->sp != sfstdin)
            sfclose(tp->sp);
      tp->sp = 0;
      return -1;
}

int
b_tail(int argc, char** argv, void* context)
{
      static const char header_fmt[] = "\n==> %s <==\n";

      register Sfio_t*  ip;
      register int            n;
      register int            i;
      register int            delim = '\n';
      register int            flags = HEADERS;
      char*             s;
      char*             t;
      char*             r;
      char*             e;
      char*             file;
      Sfoff_t                 offset;
      long              number = 10;
      unsigned long           timeout = 0;
      struct stat       st;
      const char*       format = header_fmt+1;
      size_t                  z;
      Sfio_t*                 op;
      register Tail_t*  fp;
      register Tail_t*  pp;
      register Tail_t*  hp;
      Tail_t*                 files;

      cmdinit(argv, context, ERROR_CATALOG, 0);
      while (n = optget(argv, usage)) switch (n)
      {
          case 'q':
            flags &= ~HEADERS;
            break;
          case 'v':
            flags |= VERBOSE;
            break;
          case 'r':
            flags |= REVERSE;
            break;
          case 's':
            flags |= SILENT;
            break;
          case 'h':
            if (opt_info.num)
                  flags |= HEADERS;
            else
                  flags &= ~HEADERS;
            break;
          case 't':
            flags |= TIMEOUT;
            timeout = strelapsed(opt_info.arg, &s, 1);
            if (*s)
                  error(ERROR_exit(1), "%s: invalid elapsed time", opt_info.arg);
            break;
          case 'l':
            flags |= LOG;
            break;
          case 'f':
            flags |= FOLLOW;
            break;
          case 'c':
            delim = -1;
            if (*opt_info.arg=='f' && opt_info.arg[1]==0)
            {
                  flags |= FOLLOW;
                  break;
            }
            /* Fall Thru */
          case 'n':
          case 'N':
            flags |= COUNT;
            s = opt_info.arg;
            number = strton(s, &s, NiL, 0);
            if (n=='c' && *s=='f')
            {
                  s++;
                  flags |= FOLLOW;
            }
            if (*s)
            {
                  error(2, "%c requires numeric argument", n);
                  break;
            }
            if (*opt_info.arg=='+' || *opt_info.arg=='-')
                  number = -number;
            if (opt_info.option[0]=='+')
                  number = -number;
            break;
          case ':':
            /* handle old style arguments */
            s = argv[opt_info.index];
            number = strtol(s, &s, 0);
            if (s!=argv[opt_info.index])
                  flags |= COUNT;
            while (n = *s++)
            {
                  switch(n)
                  {
                      case 'r':
                        flags |= REVERSE;
                        continue;
                      case 'f':
                        flags |= FOLLOW;
                        continue;
                      case 'b':
                        number *= 512;
                        delim = -1;
                        continue;
                      case 'c':
                        delim = -1;
                        continue;
                      case 'k':
                        number *= 1024;
                        delim = -1;
                        continue;
                      case 'l':
                        delim = '\n';
                        continue;
                      case 'm':
                        number *= 1024 * 1024;
                        delim = -1;
                        continue;
                      default:
                        error(2, "%s", opt_info.arg);
                        break;
                  }
                  break;
            }
            if (n==0)
            {
                  opt_info.offset = (s-1) - argv[opt_info.index];
                  if (number==0 && !(flags&COUNT))
                        number = (opt_info.option[0]=='-'?10:-10);
                  number = -number;
            }
            break;
          case '?':
            error(ERROR_usage(2), "%s", opt_info.arg);
            break;
      }
      argv += opt_info.index;
      argc -= opt_info.index;
      if (flags & REVERSE)
      {
            if (delim < 0)
                  error(2, "--reverse requires line mode");
            else if (!(flags & COUNT))
                  number = 0;
            flags &= ~FOLLOW;
      }
      if ((flags & (FOLLOW|TIMEOUT)) == TIMEOUT)
      {
            flags &= ~TIMEOUT;
            timeout = 0;
            error(ERROR_warn(0), "--timeout ignored for --noforever");
      }
      if ((flags & (LOG|TIMEOUT)) == LOG)
      {
            flags &= ~LOG;
            error(ERROR_warn(0), "--log ignored for --notimeout");
      }
      if (argc <= 1)
            flags &= ~HEADERS;
      if (error_info.errors)
            error(ERROR_usage(2), "%s", optusage(NiL));
      if (flags & FOLLOW)
      {
            if (!(fp = (Tail_t*)stakalloc(argc * sizeof(Tail_t))))
                  error(ERROR_system(1), "out of space");
            files = 0;
            while (s = *argv++)
            {
                  fp->name = s;
                  fp->sp = 0;
                  if (!init(fp, number, delim, flags))
                  {
                        fp->expire = timeout ? (NOW + timeout + 1) : 0;
                        if (files)
                              pp->next = fp;
                        else
                              files = fp;
                        pp = fp;
                        fp++;
                  }
            }
            if (!files)
                  return error_info.errors != 0;
            pp->next = 0;
            hp = 0;
            for (;;)
            {
                  if (sfsync(sfstdout))
                        error(ERROR_system(1), "write error");
                  sleep(1);
                  n = 0;
                  pp = 0;
                  fp = files;
                  while (fp)
                  {
                        if (fstat(sffileno(fp->sp), &st))
                              error(ERROR_system(0), "%s: cannot stat", fp->name);
                        else if (st.st_size > fp->last)
                        {
                              n = 1;
                              if (timeout)
                                    fp->expire = NOW + timeout;
                              fp->last = st.st_size;
                              z = st.st_size - fp->size;
                              i = 0;
                              if ((s = sfreserve(fp->sp, z, SF_LOCKR)) || (z = sfvalue(fp->sp)) && (s = sfreserve(fp->sp, z, SF_LOCKR)) && (i = 1))
                              {
                                    r = 0;
                                    for (e = (t = s) + z; t < e; t++)
                                          if (*t == '\n')
                                                r = t;
                                    if (r || i && (r = e))
                                    {
                                          if ((flags & (HEADERS|VERBOSE)) && hp != fp)
                                          {
                                                hp = fp;
                                                sfprintf(sfstdout, format, fp->name);
                                                format = header_fmt;
                                          }
                                          z = r - s + 1;
                                          fp->size += z;
                                          sfwrite(sfstdout, s, z);
                                    }
                                    else
                                          z = 0;
                                    sfread(fp->sp, s, z);
                              }
                              goto next;
                        }
                        else if (!timeout || fp->expire > NOW)
                              goto next;
                        else
                        {
                              if (flags & LOG)
                              {
                                    i = 3;
                                    while (--i && stat(fp->name, &st))
                                          sleep(1);
                                    if (i && (fp->dev != st.st_dev || fp->ino != st.st_ino) && !init(fp, 0, 0, flags))
                                    {
                                          if (!(flags & SILENT))
                                                error(ERROR_warn(0), "%s: log file change", fp->name);
                                          fp->expire = NOW + timeout;
                                          goto next;
                                    }
                              }
                              if (!(flags & SILENT))
                                    error(ERROR_warn(0), "%s: %s timeout", fp->name, fmtelapsed(timeout, 1));
                        }
                        if (fp->sp && fp->sp != sfstdin)
                              sfclose(fp->sp);
                        if (pp)
                              pp = pp->next = fp->next;
                        else if (!(files = files->next))
                              return error_info.errors != 0;
                        fp = fp->next;
                        continue;
                  next:
                        pp = fp;
                        fp = fp->next;
                  }
            }
      }
      else
      {
            if (file = *argv)
                  argv++;
            do
            {
                  if (!file || streq(file, "-"))
                  {
                        file = "/dev/stdin";
                        ip = sfstdin;
                  }
                  else if (!(ip = sfopen(NiL, file, "r")))
                  {
                        error(ERROR_system(0), "%s: cannot open", file);
                        continue;
                  }
                  if (flags & (HEADERS|VERBOSE))
                        sfprintf(sfstdout, format, file);
                  format = header_fmt;
                  if (number <= 0)
                  {
                        sfset(ip, SF_SHARE, !(flags & FOLLOW));
                        if ((number = -number) > 1)
                              sfmove(ip, NiL, number - 1, delim);
                        if (flags & REVERSE)
                              rev_line(ip, sfstdout, sfseek(ip, (Sfoff_t)0, SEEK_CUR));
                        else
                              sfmove(ip, sfstdout, SF_UNBOUND, -1);
                  }
                  else
                  {
                        sfset(ip, SF_SHARE, 0);
                        if ((offset = tailpos(ip, number, delim)) >= 0)
                        {
                              if (flags & REVERSE)
                                    rev_line(ip, sfstdout, offset);
                              else
                              {
                                    sfseek(ip, offset, SEEK_SET);
                                    sfmove(ip, sfstdout, SF_UNBOUND, -1);
                              }
                        }
                        else
                        {
                              op = (flags & REVERSE) ? sftmp(4*SF_BUFSIZE) : sfstdout;
                              pipetail(ip, op, number, delim);
                              if (flags & REVERSE)
                              {
                                    sfseek(op, (Sfoff_t)0, SEEK_SET);
                                    rev_line(op, sfstdout, (Sfoff_t)0);
                                    sfclose(op);
                              }
                              flags = 0;
                        }
                  }
                  if (ip != sfstdin)
                        sfclose(ip);
            } while (file = *argv++);
      }
      return error_info.errors != 0;
}

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