PsL Monthly 1993 December/PSL Monthly Shareware CD-ROM (December 1993).iso/prgmming/dos/c/snippet.exe/TAIL.C

C/C++ Source or Header | 1991-09-23 | 4.9 KB | 196 lines

/******************************************************************************
TAIL.C  Display the last "n" lines of a file (5 lines by default).
Written February 4, 1986 by Joe Huffman
Modified October 5, 1986 by Joe Huffman
  Utilize prototyping, fixed a bug, added (a few) comments and help.

Not copyrighted.

NOTE:  Compile using Datalight 'C' with flags "-mci".  Link with "_main.obj" to
get wildcard expansion of file names.

Notice the use of "atoi ()" instead of sscanf () and the use of a local int to
ascii routine instead of printf () to save space in the final executable code.
******************************************************************************/

#include <stdio.h>

unsigned char head1[] = {"\n------- \""},
              head2[] = {" -------\n"};
FILE *fp;
int filenum, cc;
unsigned int linenum = 5, indx;
long int *tail;
void help (void);

main (argc, argv)
int argc;
unsigned char *argv[];
{
  if (argc <= 1)
  {
    help ();
    exit (1);
  }

  getlinenum (argc, argv);

  for (filenum = 1; filenum < argc; ++filenum)
  {
    if (*argv[filenum] == '/')
      continue;
    fp = fopen (argv[filenum], "rb");
    if (!fp)
    {
      fputs (head1, stderr);
      fputs (argv[filenum], stderr);
      fputs ("\" not found.", stderr);
      fputs (head2, stderr);
    }
    else
    {
      fputs (head1, stdout);
      fputs (argv[filenum], stdout);
      gettail ();
      fputs (head2, stdout);
      for (cc = getc (fp); cc != EOF; cc = getc (fp))
        fputc (cc, stdout);
      fclose (fp);
    }
  }
}
/******************************************************************************
Get the number of lines to display at the "tail" of each file from the command
line.
******************************************************************************/
getlinenum (n, str)
int n;
unsigned char *str[];
{
  int atoi (char *);

  for (--n; n; --n)
  {
    ++str;
    if (**str == '/')
    {
      linenum = atoi (*(str) + 1);
      if (linenum <= 0)
        linenum = 5;
    }
  }
  linenum++;  /* Because we save a pointer to the end of the PREVIOUS line. */
}
/******************************************************************************
Set the file pointer "fp" to "linenum - 1" lines before the end of the file.
******************************************************************************/
gettail ()
{
  unsigned char outstr[15];
  void *malloc (unsigned int);
  unsigned long int currline = 0L;

  tail = (long int *)malloc (sizeof(*tail) * linenum);
  if (!tail)
  {
    fputs ("Insufficient memory.", stderr);
    exit (1);
  }
  tail[0] = ftell (fp);
  indx = 0;

  for (cc = getc (fp); cc != EOF; cc = getc (fp))
  {
    if (cc == '\r')
    {
      ++currline;
      cc = getc (fp);
      if (cc != '\n')
        ungetc (cc, fp);
      ++indx;
      indx %= linenum;
      tail[indx] = ftell (fp);
    }
    else
    {
      if (cc == '\n')
      {
        ++currline;
        cc = getc (fp);
        if (cc != '\r')
          ungetc (cc, fp);
        ++indx;
        indx %= linenum;
        tail[indx] = ftell (fp);
      }
    }
  }
  fputs ("\" ", stdout);
  ltoa (currline, outstr);
  fputs (outstr, stdout);
  fputs (" lines", stdout);
  if (currline >= linenum - 1)
  {
    indx++;
    indx %= linenum;
  }
  else
    indx = 0;

  if (fseek (fp, tail[indx], 0) == -1)
  {
    fputs ("\nFile seek error.", stderr);
    exit (1);
  }
  free (tail);
}
/******************************************************************************
long integer to ASCII.  Use this function rather than function in the library
to save many bytes in the ".COM" file.
******************************************************************************/
ltoa (val, cp)
long int val;     /* the number to convert */
unsigned char *cp;    /* the address of the string */
{
  unsigned char tempc[15], *tcptr;
  int sign;
  static unsigned char dig[] = {"0123456789"};

  if (val < 0)
  {
    val = -val;
    sign = 1;
  }
  else
    sign = 0;

  *(tcptr = tempc + 11) = '\0';
  do
  {
    *--tcptr = dig[(int)(val % 10)];
  }while (val /= 10);
  if (sign)
    *--tcptr = '-';
  strcpy (cp, tcptr);
}
/******************************************************************************
Tell the user what the program is and how to use it.
******************************************************************************/
void help ()
{
  char *ptr;
  static char help_str[] =
  { "\
Command error: No file(s) specified.\n\
Written by Joe Huffman.\n\
TAIL is a program that prints out only the last lines of a program.\n\
usage:\n\
       TAIL filename [filename] [/n]\n\n\
            filename - The name of a valid file, wildcards accepted.\n\
            n - number of lines to print out, 5 by default."
  };

  for (ptr = &help_str[0]; *ptr; ptr++)
    fputc (*ptr, stdout);
}